Cooling System:                                                                                             FAQ Home
Volvo Maintenance FAQ for 7xx/9xx/90 Cars                                                                                                                     Version 5.0
Water Pump

Water Pump Gaskets Wonít Seal

Water Pump Line Replacement

Thermostat Replacements

Draining Engine Coolant

Block Drain Plugs Location

Engine Flush Procedure

Radiator Screen

Radiator Fin Cleaning

Volvo Radiator Destructive Test

Replacement Radiators

Engine Freeze Plugs

Sudden Loss of Coolant and Engine Overheating Incidents

Loss of Coolant Sensor Design

Loss of Coolant and Possible Head Gasket Leaks

Temp Gauge Acts Oddly: Leaking Headgasket?

Thermostatic Fluid Clutch Fan Test

Oil in Coolant Bottle on 745 with B230F

Gauge Shows Overheating

Gauge Shows Intermittent Redline

Overheats with A/C On

Coolant Sensor Loose in Replacement Metal Radiator

Electric Cooling Fan Operation

Electric Fan Will Not Shut Off

Questions on Fan Clutch and Electric Fan Conversion

Installation of Electric Fan

Coolant Loss: How to Diagnose?

960 B6304 Coolant Loss: Coolant Cap At Fault

Dexcool Coolant

Homemade Cooling System Pressure Tester

Water Pump: Check out the following Web site for detailed instructions from Cameron Price regarding a B230 water pump  When you tighten the belts, be careful about belt tension. I replaced a half dozen pumps on my cars until I started leaving the belt looser. Now, they last a long time. Watch the final tightening on the alternator bolt as it will almost certainly end up taking slack out of the adjustment as you give it your final snugging.

[Query:] On a typical water pump installation, is some kind of sealant, like RTV, needed, or, just the paper gasket? If, RTV is used, where does it go? On the gasket-to-pump, or gasket-to-head?  [Response 1: Chip Hewette ] Only use the paper gasket!  Carefully align the paper gasket using the two studs on the engine block, then apply the pump. Tighten nuts and bolts carefully, snugging them down in a crossing pattern. The pump is aluminum, and you risk a seal failure if you tighten one bolt fully before all the others are nearly tight.  [Response 2:  Dick Riess] Use the paper gasket only AND clean mating surfaces, including the bottom of head mating surface. [Response 3: Don Foster] You ask different people, you get different opinions. I like to use a touch of (red) RTV on the top O-ring and on the heater pipe O-ring. In the past I've used Permatex aircraft gasket cement on the paper gasket -- it works, and I've never had a failure. BUT it's a b*tch to remove next time around.   So I install the gasket dry. Dick's caution about clean mating surfaces is critical, and Chip is absolutely right about tightening carefully and using a cross pattern.   Don't forget to pry the pump up toward the head before tightening -- this compresses the top O-ring. Also, a touch of anti-seize on the bolt threads might make removal easier next time (but don't over-tighten).  [Response 4: Randy]  Make sure the surface of the block is scraped clean before installing a new gasket (razor blade) and don't ever consider reusing the rubber pieces. I use a light smear of silicone on the heater pipe before putting the Oring on there and then another light coating on that Oring before pressing the pump on (the silicone acts as a lube and helps prevent hanging up, tearing, or twisting; but don't use so much as to have it squeeze out inside) I put a coating of silicone in the groove that the large rubber piece fits in before installing it. I put a coating of silicone on the top of the rubber piece before hanging the waterpump on the two studs. I start the remaining bolts before running the nuts on the studs down with my fingers. Using a hammer handle I apply upward pressure on the bottom of the waterpump to compress the large rubber ring. While maintaining that pressure I snug up the two nuts enough to hold the pump in that position, then I tighten the remaining bolts including the nut/bolt combination that holds the heater pipe in place. I try to wait overnight before adding the coolant to give the silicone a chance to set up.  [Tip: John O]  I wouldn't advise using any sealer like RTV, but spray a little silicone spray on the seals so the pump goes on easily, taking care of the small one on the water tube because it's easy to not notice it slipping out when moving the pump against it.

Water Pump Gaskets Wonít Seal. Put the seal on the pipe first make sure pipe is clean as well as bloc and head surfaces, then push the pipe with the seal attached, into the H2O pump. Hold the pump upward so they seat properly into their recesses ,and make sure you use the correct seals as two sets of seals of different sizes usually come with the pump. My guess is that the heater pipe seal is the culprit , as it often balks seating easily. I usually smear a small dab of silicone sealer on the seal to facilitate proper seating.

[Use of RTV vs.Gasket Sealer:] The Haynes manual advises to apply RTV sealant to the gasket. I understand RTV is to be used instead of a gasket. Is it absolutely necessary to use some kind of sealant with the gasket? [Response 1:] RTV may be used in lieu of the gasket but there's no real reason to substitute for a real gasket (I find RTV is more prone to leakage). The trick in putting in a new water pump is to adhere the gasket to the PUMP side only and leave the gasket-block interface free of Permatex (or whatever gasket sealant you're using). The gasket itself provides a great seal without adhesive but adhering it to the pump first assures that it won't slip when you're installing it. [Response 2:] I've replace 4 water pumps in over 15 years of Volvo ownership and never used Permetex or RTV on a pump gasket. I have used the gasket alone and nary a leak in the lifetime of the pumps. I insert two bolts to hold the gasket to the pump before mounting. after hand tightening all the bolts lever the pump upwards to allow the head to seal correctly with the rubber donut on top of the pump and torque appropriately.

Water Pump Line Replacement. Any secrets for hooking the hard water line to the pump? I'm talking about the one that attaches to the block near the coolant draincock, and then runs around behind the block. When I install a water pump, I "lubricate" the seal on that pipe and the opening in the pump with a very thin coating of red RTV. In the 8-10 water pumps I've installed, I've never had a problem, leak, or failure. I'm sure others out there would object to this practice -- but it has worked well for me since my first Volvo, a 1972 142E -- and I'm on my 15th, or so, Volvo. When I say "lubricate" I do NOT really mean lubricate. That is, DO NOT use oil or grease. Let me repeat: DO NOT use oil or grease. The RTV adds a little extra sealing property to the O-ring, and while it's still gooey, it's slippery. I find it helps the O-ring fit and seat properly into the pump. Of course, both the female opening in the pump and the end of the pipe must be clean and dirt-free, and the O-ring must be new. By the way, that pipe carries the hot antifreeze to your heater. Because it bypasses the thermostat, you get heat in the car while the radiator's still cold.

Thermostat Replacements. OE Volvo thermostats must be installed with the small venting nipple oriented upward. If incorrectly installed, an air pocket will form in the thermostat housing causing a reduction of cooling abilities. Beck/Arnley Worldparts' thermostats for most popular model Volvos are manufactured with a patented crimped design that ensures proper bleeding without regard to thermostat orientation. No problem.

Draining Engine Coolant.  [Query:] I must be missing something here. My 944 needed an antifreeze flush and refill, so off I went. I set the heater on "high", disconnected the vacuum to the water valve to make sure it was open, disconnected the upper and lower radiator hoses and drained a large quantity of coolant out of the radiator, water pump and overflow bottle. The heater hose was stuck on to the firewall pipe; not wanting to cut the hose, I did not disconnect it, thinking that the upper radiator hose disconnection would encourage the head and heater to drain. I also drained the block via the block plug screw. After refilling and draining again once, I put in what I thought was exactly half (5 qts) of the system capacity in new Dexcool antifreeze. This filled the system, so I obviously had another five qts of undrained water sitting in there somewhere. Has anyone figured out how to drain the cooling system down to zero? Can the heater actually hold that much fluid?   [Response:] You will never be able to get all the coolant out. Have you ever replaced an engine thinking you got all the fluids out only to have a mess all over the floor. The engine has areas that can't be drained unless the block is tipped over. You did as thoroughly as the job can be done. When refilling premix the coolant so that when you top off, the mixture is still 50/50 .

Bleeding Air from the Cooling System.  [Query]  After replacing a thermostat or water pump, how do I bleed the air out?  [Response: Jim McDonald]  Very little bleeding should be necessary if you put the thermostat in with the "wiggle valve"[air vent] in the right position[up].  Typically, I only have to add around a liter or so after running the car 'til the thermostat opens.

Block Drain Plugs Location.  [Query:] B230F - I want to flush the cooling system, but the only block drain I see is a threaded male plug on the RH side of the block (kinda high) between jugs 1 and 2. Is that all there is?  [Response: Randy] Passenger's side, #4 cylinder back. 13mm wrench will loosen, continue to turn counterclockwise and the coolant will flow out. You can attach a hose and run it into a container with about a 2 gallon capacity. If it hasn't been used in some time you may have to clean it out to get a good flow.  [Response 2:  Paul Seminara] Randy nailed it...go further back on the block way back by the tranny on the passenger side, I usually unscrew the whole works.

Engine Flush Procedure.  [Tip from Dick Riess] If you pull your thermostat, open the block drain and turn your heater valve on you can flush the engine very nicely, especially if you pull your bottom radiator hose from the water pump. Put your hose in the top where the thermostat is removed and flush. Put your hand over the waterpump opening , fill the engine till it comes out the thermostat opening and take your hand away. Do this a few times and it should come clean.   Now put the hose in the waterpump openting and flush the upward direction. The block drain will be running all this time so you are getting a good flush. When the water is clean, let it drain, tighten block drain, replace hoses and you may want to put a new tstat in so you are trouble free. Fill with a 50/50 solution of your favorite antifreeze.  [Tip from WBain] After flushing just hook the system back up and pour 5 quarts of your favorite 100% coolant into a 10 quart capacity system, and top up with water, at least to the expansion tank. I like to use 50/50 mix in the expansion tank. You should have 50% coolant/water mix, or slightly more (by 1/2 the amount of 50/50 mix added in the expansion tank).

Radiator Screen.  [Tip from Roland P.] For more than 20 years I have used fiberglass house screen in from of my Volvo 72, 81 and 91 radiators. This keeps insects from plugging air passages. Anything smaller than screen opening passes through; larger insects (leaves/dirt also) stick on there and fall down when engine stops. It seems to prevent these bugs from cooking in there. Radiators seems to last longer also.

Radiator Fin Cleaning.  [Tip from Pomp] My Volvo's been having all the same overheating symptoms I've been reading about on the board . . . running into the red and staying there. I too put in a new thermostat and did a flush but it still ran hot. I then sprayed out the radiator fins from the engine side out.   Yesterday we ran into 99-degree heat and it never once ran hot.  [Tip from Ed Lipe] Always blow back to front with air. You run the risk of making a mud-pack if you just make a passing attempt with water.  The generic blower schnozzle on the end of a compressed air line works well. You often get to nick your knuckles on the fan and shroud and other goodies down there. Yes, you do have to reach.  I've made a modification to my blower. Usually there is a fitting screwed into the end of the blower, and it is usually 1/8" NPT pipe thread. I've added a 1/8 NPT x 1/4" tubing compression fitting with about 2 feet of 1/4" copper tubing or the stiffer brake tubing.   With this, you can reach some tight places with little problem. I use mine nearly every day to clean coolers and radiators. I start from the rear and then go to the front and then again from the rear just to make sure it's clear.   After a good blow out a hose down is also good, but the air is usually enough. Make it a regular part of your maintenance regimen.

Volvo Radiator Destructive Test. As I am basically a chicken, I decided after this summer's rash of "radiator failed and I lost my coolant" messages to buy a new Nissen unit from RPR and install it in my 1990 745. The 745 was built in July, 1989, so the original Blackstone aluminum/plastic radiator was exactly ten years old, in the age range where I began to worry that I would lose it catastrophically some hot summer day. It showed no evidence of leakage or corrosion, but then reports show that the plastic side tanks fail first, and usually through a large crack. I used Volvo blue-green for the first six years, switching to Havoline Dexcool orange in 1996. Coolant has been changed every two years.
The installation of the Nissen was a piece of cake. The new unit is at least twice as heavy as the old one, the result of brass and not aluminum construction. While removing the top hose from the old radiator, I pulled off the inlet hose plastic fitting, so some plastic embrittlement was evident. I also found that the fins on the old unit were absolutely filled with dirt, bugs and assorted crud. When I banged on it, lots of dirt fell out.
After finishing the job, I decided to do a little destructive testing on the old unit. I used a ball peen hammer and whacked the plastic side tanks to see where they would fail. They were actually quite robust for 3mm thick plastic, but I found that the weakest area was around the inlet area on the top,  which makes sense because the hottest water enters at that point and any temperature-related plastic fatigue would tend to start there. That cracked far more easily than the outlet area, which tends to stay cooler in operation.
I then peeled back the tabs holding the side tanks and removed the tanks. Amazing! There was absolutely no evidence of any internal corrosion whatsoever. Each tube was in pristine shape, the header ends appeared brand new, and the transmission cooler was in superb condition. The rubber gaskets sealing the joint between the tanks and the radiator shell were elastic and clean. The only thing I noticed was a little bluish-green silicate precipitate film on the surface of the side tank near the outlet fitting (the coldest area of the radiator) related to the pre-1996 Volvo coolant that I used. Otherwise everything was clean.
The only weak point in the radiator was the embrittled plastic on the upper side tank near the inlet hose.  Otherwise, these are very high quality units (and I speak from experience with mid-80's GM radiators, which corrode and fail every five years.)
My recommendations to everyone are:
 -Make sure you change the coolant regularly;
 -Dexcool seems to work very, very well in an all-aluminum radiator;
 -Pull the fan shroud back (two bolts, easy!) and use compressed air or a car wash high-pressure soaping wand to blow out the dirt from the fins.
 -Think about changing the radiator after ten years when side tank plastic embrittlement will become a problem. Due to the nature of the aluminum tabs holding the tanks in place, it does not appear possible to replace the tanks alone, since in doing so you will crack the tabs.
I hope the Nissen unit will have the same robust metallurgy and last just as long.
[Response 2: Dick Riess] Your experience with the top inlet being weak dovetails with my experience in at least three instances. One actually broke in my hand when changing hoses.

Replacement Radiators: Wholesale Radiator lists $128 for an all metal radiator for an 87 760T, for example. Guaranteed for as long as you own the car.1-800-204-2020. [Source: Thailand.] Buy the IPD unit. I've had one for four years, with zero problems. It's literally a remove & replace, right own to the correct fittings for sensors and tubes. One caveat, however: Volvo coolant tends to eat these, as they apparently use a formulation for aluminum parts that eats copper and bronze. I'm now on my second one for that reason. This time, I'll be using Prestone. [Other info:] Summary: 1) The only radiator available locally was a "Modine". 2-row,brass+copper. price ranging from $154-190. No reports on quality received. 2) IPD offers a 3-row radiator made in Denmark by an unnamed company(probably not Nissens). I was unable to determine whether or not they are still sourcing the same unit that some netters have had problems with. 3) Rob at Wholesale Radiator Warehouse in Cincinnati OH (800-322-1616)was very helpful. He had a 2-row "Auto Radiator Sales (ARS)" brand all-metal radiator for $123 inc s/h. He said he could special order a 3-row "CSF" brand radiator for $215 inc s/h. No reports received on quality of ARS; one positive report on CSF (see below). I hear CSF is made in Taiwan. 4) I got several positive recommendations for the Nissens 3-row all-metal radiator. Made in Denmark. Has a screw cap to hold in thermoswitch (or plastic plug in my case). Comes with transmission cooler for auto trans. From RPR. Available from: GAPA $260+s/h Global Automotive Parts Access (GAPA)27068 La Paz Road, Suite 507 Laguna Hills, CA 92656(714)581-3427,,  G&G ~$245 Wisconsin - has listing in Rolling RPR $219+s/h 599 San Pablo Ave. Albany, CA 94706 (510) 524-7200 ; FAX 510.524.7409800-81-VOLVO (800-818-6586) Josh answered all my questions quite thoroughly. 17lbs shipped to NY was $14.

[Comment:] The quality of aftermarket radiators vary considerably. The brand I use in my shop is "Nissens". One of the nice features of this radiator is the screw cap that holds the sensor in place.

Nissen Radiator Composition.   [Tip from A. Sorenson at]  Our solder composition is 33% tin and 77% lead [Editor: thereby qualifying as "low-lead".]

Engine Freeze Plugs: We in the great white north (Canada) refer to these casting plugs as "frost plugs"; they are intended to pop in the event that the engine is filled with water rather than anti-freeze and the temperature drops below freezing-they are sacrificial in order to save the block from cracking. The one below plug two is actually removable in order to insert a block heater, in fact these plugs and block heaters both corrode with equal regularity (about once every 150,000-250,00 kms) and fall out causing loss of coolant and if not detected, overheating... a quick and inexpensive repair in either case unless, of course, not detected in time. Keep watching those temp gauges.

Sudden Loss of Coolant and Engine Overheating Incidents.   [Steve Ringlee] We recently surveyed the Brickboard and Swedishbricks lists for incidents of sudden loss of coolant and engine overheating.  Here are the results:
 -Plastic-bodied heater water valve cracked; coolant was pumped out
In most of the incidents, drivers did not notice the loss because the coolant was pumped or blown under the car.  In most cases, the first evidence was engine noise, slowing of the car, or other signs of serious engine damage.  [Steve Seekins:] these valves crack longitudinally along the plastic center pipe.
-Heater hose fractured due to aging and internal crack; catastrophic loss of coolant
-Heater hose chaffed against block, rubbing through and failing; catastrophic loss of coolant
-Radiator plastic side tank fractured; catastrophic loss of coolant
-Radiator hose split due to aging and internal crack.  Upper: loss of coolant; lower: catastrophic loss of coolant
-Top radiator hose clamp was over-tightened, cracking plastic neck outlet. Some coolant was pumped out and the engine temp gauge showed overheating but no damage occurred.
-Hose clamp failed; lower radiator hose parted from radiator outlet neck.  All the coolant suddenly drained out of the radiator, leaving only the coolant in the block.  Engine required a new headgasket.
-Coolant Reservoir Hose Became Oil-Soaked at the Clamp and Split.  All coolant was pumped out and the engine overheated.
-Water pump seized due to a bearing failure around the pump shaft, shucking one of the two drive belts.  The remaining belt was sufficient to start the pump turning again, but this resulted in the cast iron pump impeller coming into contact with the back of the pump casing, smashing it and causing loss of coolant.
-Electric frost plug engine heater leaked due to corrosion of the anchoring devicel; slow leak.
-Nobody mentioned a failed water pump shaft seal as a cause of catastrophic loss-of-coolant, merely resulting in slow leaks.

In almost every case, the lack of an "idiot light" caused drivers not to notice the loss until too late.  When the driver finally looked at the temperature gauge, it was invariably far into the red zone, indicating serious overheating.  In almost every case, drivers attempted to drive to a convenient destination such as home, a gas station, or a freeway exit.  This extended drive usually led to further engine damage.   The least damage noted (except in the last instance) was head gasket; in many instances the engine required replacement.

Lessons learned:
1. Assume that your cooling system components have a limited lifespan.  Replace them according to an intelligent schedule.  I replace hoses every six years and the radiator and water valve at year ten.  I replace the water pump either at a convenient maintenance interval or when it starts leaking at the seal.  For turbo cars, assume that the higher underhood temperatures will reduce component lifetimes.
2. Give serious thought to installing a loss-of-coolant sensor and an idiot light wired into your instrument cluster.  "I didn't notice until it was too late" was a universal experience.
3. If you notice smoke, fluid or other evidence of engine distress, STOP and see what the matter is before trying to go any further.  Shut the engine off if you have a loss-of-coolant or oil.

Loss of Coolant Sensor for Volvo 740/940 Cars:  [from Steve Ringlee]

These plans allow you to fabricate and install a low-coolant sensor in your car so that you can detect either slow or sudden coolant leaks and take appropriate action before your engine overheats.  Volvo 760 and 960 cars have these sensors already installed.

Overall Plan.

a) Volvo 740 with Circular Oval Tank.

Using a Nohken float level sensor switch, drill a hole in the bottom of the coolant tank and install the sensor.  One lead is wired to the front grounding plane near the passenger-side headlight, the other back around the engine compartment, through the firewall, to the unused instrument panel lamp denoted "EGR Overheating (Japan Only)."  When coolant is low, the switch closes, allowing 12V from the panel to travel through the switch to ground, illuminating the warning lamp.  You can add a small piezo buzzer to add an audible warning, if desired.  The circuit is fused just behind the panel.

b) Volvo 940 with Rectangular Tank P/N 9142001/2

Volvo included a level float in this tank, but not the sensor.  Buy a "Level Guard" sensor Volvo p/n 3547710 and wire as above.  Make sure you read all assembly instructions below first, especially to confirm you have the float inside the tank.

Bill of Materials:

    740 Variant: Float Level Sensor Switch: Nohken LS-11P-0A, miniature 10VA switch with polypropylene float and stem and flat flange face. This is available from Scientific Technologies Inc. at 6550 Dumbarton Circle, Fremont, CA  94555-3611, 510-608-3400.
        Order STI part number 22152; cost is approximately $15 plus shipping. Web site is
    940 Variant: Volvo "Level Guard" p/n 3547710)  approx $15 from Borton's Volvo, or from a junkyard off a wrecked 960 car.
b) Volvo 12v 1.2w lamp for instrument panel:   Volvo uses two kinds of bulbs and bulb holders for their panels.  One is a replaceable bulb with wire leads, inserted into a holder that has a plastic locking ring.  The other is a bulb soldered into a holder with metal locking tabs.  You will probably have to pull your panel to determine which one your car has.
740 with Yazaki panel:  Volvo p/n 2721 1.2w replaceable bulb with leads
940 with VDO panel:  Volvo p/n 966326-1 1.2w bulb fixed into holder

c) Instrument panel female metal electrical connector inserted into "C" harness connector:
        a.  740 and 940 before 1994: ell-shaped "C" connector uses Volvo p/n 949542 (likewise "L" shaped)
        b.  940 1994+: flat "C" connector uses flat Volvo p/n 9148152

d) Electrical Supplies, all from Radio Shack (one each unless noted):
Insulated Wire:  20 gauge stranded approx 25 feet p/n 278-1225
Snap Connector 22-18 g, p/n 64-3085
Inline Fuse Holder 5x20mm p/n 270-1238C
GGS 5x20mm Fast-Acting Fuse 3/4 amp p/n 270-1048
Quick Disconnect Connector, Female, .25 inch, p/n 64-4040
Crimp Butt Connector, 22-18 gauge (quantity=2) p/n 64-3037
Shrink tubing for insulating connections p/n 278-1611
Option: Piezo buzzer p/n 273-059 (gives audible warning)
Soldering iron with electronic solder

e) Mechanical Supplies:
Wire ties for securing wire to existing harnesses
"OxGard" conductive electrical grease (from hardware store)
Silicone dielectric insulating grease (from auto parts store)
Volvo 940 applications:  None other required
Volvo 740 applications:  (from hardware store)
Neoprene O-Ring O.D. 1/2 inch, I.D. 3/8 inch
Neoprene Flat Washer O.D. 7/8 inch, I.D. 3/8 inch

f) Volvo wiring diagram to understand your panel connectors.  Here is where Chilton's will finally choke you, and you will be motivated to buy the OEM wiring diagram which is absolutely the best on the market.  Approx. $30 from Ken Cook Inc. (Volvo agent) at

Assembly Instructions:

1. Volvo 940:
a) Drain coolant recovery tank and remove from car.  Shake the tank to make sure that Volvo installed the magnetic float that activates the Level Guard inside the tank.  (It rattles.  If you can't hear the rattle, install the Level Guard and test it with a multimeter for resistance change as the tank is filled with water.) If your tank has the float,  install the "Level Guard" sensor into the snap hole on the bottom of the tank.  Insert the wire leads into the tank's wiring connector holder on the bottom.  Continue below at step "e)".
If you don't have a magnetic float inside, you can either proceed as though you own a 740, or buy a new tank with a float from Borton's for about $25.
Volvo 740:
a) Drain coolant recovery tank and remove from car.
b) Drill a 10mm hole on the flat surface of the underside, approximately one inch toward the center from the threaded cap
c) Remove the float and install it so that the switch operates in the "N.O." ("Normally open") position.   Test the switch operation with the ohmmeter range on a multimeter: when the float is at the bottom of the switch (corresponding to loss-of-coolant) the switch should close and complete the circuit, reducing resistance from infinite to zero.
d) Remove the fixing nut on the bottom of the coolant sensor switch.  Install the flat neoprene washer on the switch. Feed the switch wires through the coolant fill hole, then into the hole you drilled on the bottom of the tank.  Pull the switch snug.  Install the neoprene o-ring, then the fixing nut.  Snug up the nut until the switch is firmly held without possibility of leakage.  If your hole was oversize, use silicone RTV to seal the gap between the hole and your o-ring.
e) Cut a piece of wire sufficient to reach the grounding panel just behind the headlight.  Using a short piece of shrink tubing and a .25 inch female blade quick connector, crimp the connector onto a stripped end of the wire and add some solder to ensure a long-lasting connection.  Shrink the shrink-fit tubing onto it at the crimp to serve as corrosion proofing.  Clean off the grounding plane connector, install the blade connector and the wire onto the ground, insulate it with some "Oxgard" conductive grease, then feed the wire up the lamp harness back to the coolant tank.  (Maintenance note: this is a good opportunity to clean all your grounds and coat with OxGard to prevent future electrical problems.  Don't use OxGard on any other connectors in the car aside from grounds.)
f) Volvo 740: Install a snap connector to one wire of the float switch and the ground wire.  Again, solder it.  Insulate any exposed wire on the connector with shrink tubing.  This connector allows you to disconnect the level sensor easily.
Volvo 940:  Using a razor knife and some pliers, cut down the diameter of two female snap connectors and squeeze them so as to fit very tightly on the Level Guard lead connectors.  Install one of these snap connectors onto the stripped lead of the ground wire by firmly crimping it.  Place silicone dielectric grease on the connection for corrosion protection and connect the ground wire connector to one of the Level Guard leads.  If you are ambitious, buy the un-insulated version of the snap connectors, solder them onto the wire, and insulate with shrink tubing.
g) Cut a long length of wire sufficient in length to travel from the coolant tank, up the wiring harness at the top of the firewall, thence through the firewall rubber wiring conduit behind the driver-side strut tower, thence into the cabin with an excess of length to reach well beyond the panel.
h) Volvo 740:  Strip, crimp, and solder one end of this wire (using a crimp connector) to the other sensor switch wire.  Insulate where exposed with shrink tubing and apply silicone dielectric grease to the ends of the connector to prevent corrosion.
Volvo 940: Install the other female snap connector onto the stripped lead of the panel wire by firmly crimping it onto the stripped end.  Place silicone dielectric grease on the connection for corrosion protection and connect the ground wire connector to the other Level Guard lead.  Again, if you are ambitious, buy the un-insulated version of the snap connector, solder it onto the wire, and insulate with shrink tubing.
i) Snake the other end of the wire up to the firewall harness and to the lower firewall rubber wiring conduit just behind the driver strut tower.  Use wire ties where appropriate.
j) Cut off one of the smaller rubber wiring conduits in the lower firewall connector just behind the strut tower.  Feed the wire through the conduit into the cabin.
k) Remove the battery negative connector to disable the electrical system.  Remove the driver side kickpanel (two plastic body mounts at the top, pull out.)  Move both the turn signal and wiper handles down, out of the way. Remove the instrument panel (740:  remove plastic fascia plates covering the clock and rheostat knobs, then the two screws holding the panel in place.) (760: See Link.)   (940: unclip using the two side slits midway up the sides of the bezel.  See link.)  Pull the panel straight out and rest it on the steering column.
l) Working from underneath, snake the coolant sensor wire from the back of the firewall wiring conduit up through the panel opening.  Keep it away from the hood release mechanism, any sharp metal edges, and the ignition module, using wire ties as needed.
m) Pull the large 12-position "C" plastic wiring connector out from the rear top center of the panel.  This connector is white and roughly "ell" shaped when looked at from the side (but is flat for later 940s.)
n) Confirm with your wiring diagram which connector you will use for the warning lamp.  In the 1986 740, this is position number 7, numbered on the connector itself, which is not used for any other purpose.  In the 1990 740, this is position 12 on the connector, which connects to the unused "Exhaust Gas Temperature" lamp for Japanese applications.  In the 1995 940, this is position 9 on the connector which connects to the unused "High Engine Temperature" lamp.
o) Cut the coolant sensor wire, leaving enough to reach just beyond the door opening.  Strip and install the in-line fuse holder using soldered crimp connectors and shrink tubing or insulating tape to cover exposed surfaces.  Install the fuse.  Be very careful about soldering near the interior of the car: use a metal guard or shield to keep hot solder off plastic, fabric or leather components.
p) If you want to add the piezo audible buzzer, place it in-line between the fuse and the firewall, again using crimp connectors, solder and shrink tubing.
q) Install the special ell-shaped or flat Volvo metal wire connector p/n as in the parts list above (p/n 949542 or 9148152) to the end of the fuse wire.  While this is crimped in place, you should also add a small amount of solder to secure it.
r) Record the colors and positions of the wires at the "C" connector.  Snap open the back of the connector and insert the coolant connector at the correct position.  Snap it shut, making sure all the wires go back appropriately.
s) Install the Volvo instrument panel lamp at the appropriate lamp position, again per your wiring diagram.  On the 1990 740, the lamp is installed at the second in from the driver's side of the panel, in the unused position.  In the 1995 Volvo 940, the lamp is installed at position 7 from the passenger side of the panel.  If you are confused, use a flashlight and shine it through the empty lamp receptacle to confirm the position from the front.  Just make sure from your wiring diagram that you correlate the lamp position with the wiring position in the "C" connector.
t) Re-install the "C" connector.  Coil extra wire and install a tie to keep it out of the way.  Re-install the panel.
u) Seal the wire passage through the firewall conduit with silicone caulk.
v) Test the installation.
Volvo 740: open the coolant tank and place a pencil on the float so as to depress it to the bottom.  Start the car.  The lamp should go on.  Demonstrate several times to wife and kids what this lamp looks like and what they need to do if it goes on (stop the engine ASAP and investigate.)
Volvo 940:  Using a turkey baster or a siphon, empty the coolant reservoir.  Start the car.  The lamp should go on.  See note above.

Regular Maintenance.  Because of the peculiarities of the wiring within the instrument panel, your bulb may not illuminate when you turn the ignition to KPII before starting.  Hence, periodically test the installation to make sure that the bulb, the sensor, and the circuit operate correctly by performing test v) above.

Loss of Coolant and Possible Head Gasket Leaks.  See  Headgasket Failure

Temp Gauge Acts Oddly: Leaking Headgasket?  See Temp Gauge Acts Oddly: Leaking Headgasket?

Thermostatic Fluid Clutch Fan Test. Fan should roar when car is first started cold engine. Within 5 minutes the roar should stop/die down. When radiator warms up, the roar should start again. For the thermostatic one (post ~1980), run engine, hang blanket over grille. If the fan starts to get loud and blow more air before the temperature gauge gets too high, the thermostatic clutch works. To check slippage (at normal engine temperature), Volvo suggests using a strobe light with adjustable frequency. You put a timing mark on the fan with chalk, and figure out the fan speed for a few different engine rpms. The chart of engine vs fan speed is in all the different repair manuals.

The crazy way (which I prefer), is to stick a big screwdriver in the way of the fan with the engine idling on a regular day. If the fan stops easily, but quickly spins again, then I guess it's OK. The fancy strobe light Volvo describes seems awfully expensive just to make sure your fan spins right.

Oil in Coolant Bottle on 745 with B230F.  [Query:] I own a 1991 740 wagon, 125,000 kms, B230F engine, auto, not driven particularly hard.  The problem is this:  On Sunday I discovered oil in the radiator expansion bottle. But no oil in the radiator! And no sign of oil (frothy or otherwise) on the dip stick.  I have taken the car to the local service station thinking that I have a blown head gasket. This afternoon the mechanic has shown me the dismembered bits. No blown head gasket. He is sending the head for a compression test.   So what do you think?
 [Response: Steve Seekins] On this particular car, the problem is likely the oil cooler. Check at the oil filter housing. I think that your car has a sheet metal oil cooler mounted on the oil filter extension housing just forward of the oil filter. It should have two water lines attached. These have a history of developing leaks - it may simply need to be replaced. You can remove it and perform a pressure test on it. If you have the older style cooler, there will be a cast piece there with OIL lines vice the sheet metal piece with WATER lines. The earlier cooler adapters have no water interface so cannot leak water, but do develop oil leaks from worn O-rings. [Solution: Owner]  The problem turned out to be a leaking radiator ATF cooler.  I replaced the radiator and it solved it.

Gauge Shows Overheating. [Symptom:] My temp gauge started going almost to the red (I always shut the car off to avoid a boil over) and gave readings (now that I think about it) that were generally high and also sporadic. [Diagnosis:] I pulled out my Bentley manual and it was plain as day (consistently high sporadic gauge readings) that it was the voltage regulator. I took out the voltage regulator for the temp gauge cleaned the four contacts and more "overheating."

Temp Gauge Shows Intermittent Redline.  My temp gauge would almost redline for a couple of days but then be normal for a week or a month and then repeat the symptoms. This doesn't feel like an engine that's over-heating.  [Fix:] Try loosening the block gauge temperature sender  a quarter turn then tighten. Slight corrosion at the sender's threads may interrupt circuit grounding. Worked for me anyway.

Overheats with A/C On.  [Query: 1991 740 B230F station wagon. Normally the car can sit for 10 20 or 30 minutes at idle and the temp gauge will stay in the normal spot.
However, when I run the A/C the car will over heat even if I'm running at 70 - 80 mph.]
[Response 1:] Before you go any further you should wash out your radiator to clear it of any accumulation of bugs and dirt. Many Volvo radiators are replaced for this reason and it does fix them as a new radiator is obviously clean. It could be a thermostat, bad fan clutch, head gasket problem, etc., etc. but the radiator being obstructed is an easy thing to try. Get your garden hose out and wash from the fan side towards the front of the car. If you see a lot of debris then it is worth the trouble to remove fan and fan shroud and continue to wash but more thoroughly. It helps to use Fantastic or Formula 409 as that will get more dirt off the fins of radiator and condenser. [Response 2 for B230FT:] If this has the oil cooler that is mounted off to the side, you need to clean it too. Remove one bolt at the top; it sits in a molded rubber fitting.  Be careful of the hoses! I found this to be totally clogged when the radiator was cleaned. You can't remove it without disconnecting the hoses and having a mess, but you can get at the nooks and crannies where the crud is. Don't spray at an oblique angle, because you will bend the fins.

Coolant Sensor Loose in Replacement Metal Radiator. [Symptom:] I had a metal radiator installed in my 87 765T and have had nothing but problems trying to get the temp sensor sealed in the tank (uses a rubber grommet). Just started leaking again today. Someone mentioned a screw fitting to hold the sensor, but I have been unable to rind one. I believe my radiator is a Nessen and has threads where the holes is for putting the sensor in. [Fix:] I did two things when I replaced my oem rad with a metal one. I used a brand new grommet and I pulled a wire tie through the rad and around and across the temp sensor between the two spade connectors (it needs to be a pretty long one.) This will prevent the sensor from popping out, not an unheard of scenario. [Fix 2:] I recently installed a metal radiator from RPR, I believe it is a Nessen brand, and the temp tensor fitting has a metal screw on 'lid' (with a hole cutout in the top of it) which screws down on the temp gauge after it is pressed into the rubber grommet and keeps it snugged down in it's bung (couldn't help myself). Contact RPR, they may be able to help you find a lid...

Electric Cooling Fan Operation.  [Query] I've had my 1989 740 for a year and just yesterday at the muffler shop, while the car was up on the lift, I peeked in the front end, and lo and behold there, in all its glory was an electric fan in front of the A/C radiator. However it never has turned on, that I know...How do I test it to see if it works?, where is the wiring to the sensor that turns it on?  [Response: Abe Crombie] On an 89 740 model that fan is triggered just for overheat by a switch in tank of radiator that turns on relay on strut tower that feeds power to fan.  If it is a 760 then the relay can be triggered by the aforementioned switch or by a ground out of ECC control unit if the outside temp is over 92 F +/- and you are below 8 MPH and the a/c compressor is engaged.  To test the fan, find the switch on right radiator end tank and pull back the rubber sleeves covering wires and short the two terminals together with a small screwdriver. Key must be on.  If this doesn't make the fan start then go to the relay and check for power supply on one of the two large gauge wires (one is feed and one is to fan motor, so one should be hot). If power is found then disassemble and inspect for cracked solder in relay and repair as needed.

[Electric Fan Won't Turn On] [Symptom:]Engine overheats in 940 while sitting in traffic. I have an electric fan on the front of my radiator. I have never seen it come on - What triggers this fan to come on?
[Diagnosis:] Before you buy a new fan be sure the fan is the problem. The engine *will* overheat standing still in traffic if the fan doesn't turn on to keep the water temp cool enough, especially if the A/C is on. Make sure the fan has not seized first . There is a thermostat switch on the top of the radiator on the passenger side with two wires attached to it. One wire should have voltage to it at all times (engine running). The other wire goes to the fan. If the one wire is hot touch the two together and the fan should turn on. If the fan works then you probably need a new thermostat switch. If the fan doesn't turn on and it has a proper ground *then* you probably need a fan.

Electric Fan Will Not Shut Off.  [Query:] The wife's 940 Turbowagon has an auxiliary radiator fan that seats in front of the radiator that will not shut off after she had parked the car in the garage for over an hour. I tried to look for the electrical wire in order to disconnect it but could not locate it. So the next best thing to do was to disconnect the battery because it had drained the juice in the battery. Has anyone gone through this scenario and what is causing the aux. fan to run continuously?  [Response: Wydon] I had a fan relay stick on my 960 which caused the fan to run on. I replaced it with a new one and that fixed it. Some have had good results re-soldering relays.

Questions on Fan Clutch and Electric Fan Conversion. The four nuts from the water pump pulley come off, and the two screws that hold the top of the fan shroud get removed. Grab the fan and wiggle the fan ( with the clutch still attached ) and remove the fan and shroud together. Transfer the blades and reinstall .    As far as the aux electric fan goes, you will have to fabricate some things to make it work. It will help. Don't forget to also check the basics like engine timing and boost pressure, both can create excess heat.

Installation of Electric Fan.  [Procedures and results:] installation in a 87 745 ti:

Selection: I bought a Mr. Gasket high performance electric fan, 16 inch, heavy duty plastic with ring shroud. this was about 95 bucks. I also bought an adjustable thermostat kit for about 25 bucks. It had a name brand, I think Flex-a-lite or Therma-cool, but it was universal in its application. some members suggested getting the fan and related items from a new 92 or newer 7/900 but i did not have the time to investigate and I do not know of any u-pick-it type salvage yards in the New York Area (anyone know of any?? i would love to check one out.) The fan I bought pulls 1900 cfm on 10 amps. Similar options are the Flex-a-lite, or Perma-cool. A high end option is the Spal fan which pulls 2300 cfm on 23 amps and has a thermostat that connects directly to the cylinder head but the cost is higher, 155+55... I don't know if one needs this kind of air pull but your call.


Other options: include a switch to customize when the fan will or will not work depending on where it is positioned and whether or not it provides its own power supply..

Coolant Loss: How to Diagnose?  Further information:  See Head Gasket Failure.  [Query:]  My Brick is losing coolant; is it the head gasket?  How do I tell? How do I pull the head?   [Response: Don Foster]  Pulling the head is not a casual or inexpensive job. You might even cause more problems than you now have. First, look long and hard for the leak.
If it were my car and I was worried about disappearing antifreeze, I'd carefully crack the oil drain plug, let the first few tablespoons drip into a bowl, and examine it carefully for antifreeze. It'll sink to the bottom, so should be the first out. Do this with a stone-cold engine (not run for several days).  If the antifreeze has mixed with the oil in a running engine, it'll form a "dispersion" and the oil will take on a grayish, cloudy characteristic.
Next, I'd pull each sparkplug and look for evidence of coolant in the cylinders. BTW, an engine leaking coolant into a combustion chamber will have an unusual amount of white exhaust smoke, particluarly on a cold day (steam). More typical, however, is that the combustion gasses are forced into the cooling system -- and can be detected with a simple instrument. Every garage should have one. I do.
Much more likely is a hidden leak elsewhere in the cooling system. First, look very carefully around the water pump. When the seal starts to leak, often antifreeze can "sneak" unseen down to the splash pan -- and if it's a slowish leak, you might not see a puddle 'til the leak gets worse. The antifreeze will escape only when you're driving.
Another "invisible" (but problematic) leak might be the heater core. Or even the heater control valve. If you find something around the heater (and fix it) don't forget to get the coolant out from under the carpets -- they really should be pulled. Otherwise you'll be facing rusted floors in a year, or so.
If you're really determined (and have some equipment available), get an old radiator cap and mount a barb fitting in it. Then hook a compressed air supply to the cooling system through a regulator -- you shouldn't use more than about 10 psi pressure -- 12 max.    This way you can accelerate any leak for you inspection without running the engine. [Editor's note: see Headgasket Failure for procedures on a cooling system pressure test: highly recommended that you have the correct equipment for this.]

960 B6304 Coolant Loss: Coolant Cap At Fault.  [Query:] I'm a little concerned about the accounts of casting porosity in the 6 cyl block or head. This would certainly explain my regular loss of coolant.  No external leaks, no  WP seal or gasket leaks, heater core seems OK (no smell in car, no coolant in condensate rain) no coolant indications in engine oil or ATF. Runs fine so far. Could it be leaking outboard of the exhaust valves and vaporizing in the manifold? I assume this would kill the cat or O2 sensor after a while. But no white smoke shows.   Coolant has to be going somewhere and it is doing so at the rate of about a pint a week. In winter. Perhaps more. This engine would fry and bend like a hot dog if it ever got seriously dry.  Any ideas?  [Response: Tom Irwin] Relax!   The block porosity issue was limited to about the first 10,000 units off the line in model year 1992, only!   If it was leaking into the oil, your crankcase would be full of mayonnaise, right?  Per chance, Greg, do you have a Grey plastic pressure cap?? Hmm?   If so, you need a Green one. My wifes 940 and my 960, each with grey caps, failed within 6 mos. of each other. They tend to get little hairline cracks in the threaded portion. They spittle and sputter and ooze coolant ONLY when at temp. and pressurized. Check it out carefully.   FWIW, Stant company is selling the new green Volvo caps for half what the dealer wants, under their own name.  Also, you change your coolant right? Volvo Type C blue only?  Don't believe the "Perma-Fluid" crap in your manual.

Dexcool Coolant [From the AC-Delco site:] Neon orange in color, the coolant lasts up to five years or 150,000 miles, whichever comes first. Conventional coolants need to be replaced every two years/30,000 miles. DEX-COOLís benefits include: Lower maintenance costs, due to longer change intervals; enhanced component durability -- improved water pump seal performance and superior heat exchanger protection over regular-life coolants; recyclability. Note: DEX-COOLís unique orange color acts as a reminder not to mix the new formula with conventional coolant (usually green in color). Although it wonít damage your carís cooling system when mixed with other coolants, DEX-COOL will lose some of its effectiveness. (Warning: Do not use DEX-COOL with Cooling System Seal Tabs, Radiator Fast Flush or Radiator Stop Leak.)
[Note from Texaco regarding rumored incompatibilities:] "We have seen the statement many times that "On '93 and older GM models, use of this antifreeze is discouraged because its chemical ingredients can interact with the copper-soldered joints inside the radiator." It was even in Motor Trend recently, which has spread the rumors further. The statement is not true. Havoline Extended Life Antifreeze DEX-COOL can be used in any car including 93 and earlier model GM cars without any problems.
It is true that some older GM cars used a high lead solder in copper brass radiators where their newer cars are all aluminum. However, Havoline Extended Life Antifreeze DEX-COOL protects the high lead solder very well, there is no detrimental interaction with the solder or radiator, and there is no need to be concerned. Indeed, although GM decided to be conservative in not recommending DEX-COOL for all older cars, Texaco has recommended Havoline DEX-COOL for ALL cars, and stands behind the product in ALL cars. "
[Stephen Goldberger] It is claimed by the manufacturer to leave a thinner inhibitor layer on the metal, resulting in improved heat transfer, and it is claimed to be less abrasive to the water pump seals. The inhibitor in "DexCool" is a non-silicate formulation, more along the lines of the European sebacic acid practice, but it is not the same.  The 100,000 mile or 5-year recommended change interval is only true for vehicles which had "DexCool" as original fill; otherwise, it is recommended that the original factory change interval be adhered to.
[Ywan Mason]  Dex-Cool, according to a GM service bulletin only gives the extended life when it was used as the first and only coolant in the car. Residual amounts of conventional coolants left in the system even after careful draining require that the Dex-Cool be changed at the same interval as any other coolant, every two years.
[Paul Seminara] Just got off the hook with tech. reps at Texaco. Absolutely no problems should be encountered with Dexcool and high lead solder in the Nissens radiator.   They said the GM and other concerns with the products is with 5 years in a system with lead, the coolant would be metal bearing (including lead - as would any coolant, including water!), not that the lead would degrade.   They assured me that I was very safe because of all my new system components and huge amount of flushing that I did.

Homemade Cooling System Pressure Tester. Here's what I've rigged up for both pressure testing the cooling system and bleeding the clutch and brakes: I found an old bottle cap that has the same threads as the coolant reservoir. Then I bought $1.00 worth of tank valves and screwed one into it. If you don't have such a cap, then an old coolant reservoir cap should work even better. When I need to use it, I take the gasket out of the coolant reservoir cap and use it in my "pressure cap". I connect a $5.00 bicycle pump (with built in pressure gauge) to the cap and presto. Since the brake reservoir has the same type orifice, it can also be used to pressure bleed the clutch and brakes.

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