FAQs about Flame Traps

  • Flame Trap Road map.
  • Is there a flame trap on a intercooled turbo engine?
  • I neglected to replace the flame trap....

  • Flame Trap Road map.

    Date: Fri, 17 Jan 1992 13:59:46 PST
    From: Raphael_F._Bov.wbst311@xerox.com
    Subject: Flame Trap Road Map
    To: Mike.Sestina@east.sun.com
    Cc: volvo-net@me.rochester.edu

    The flame trap is one of those little things that cost very little, but are impossible to find, harder still to remove, can only be replaced by contorsionists and monkeys and will destroy your engine if you don't change it regularly!

    I think it has something to do with PCV, but without a valve. The Haynes manual has a nice picture of the air flow at idle, under load, etc.

    That said, look in the least accessible part of the intake side of the engine, directly underneath the center of the intake manifold. It's mounted on the block in a little black plastic piece that is removable and is attached to two hoses. A small hose comes up to a nipple between the 2-3 intake runners and a wide (.75") hose runs from the throttle body area to the beastie. If a friend can show you where it is, more the better

    Getting it out is difficult, cleaning it is nearly impossible, and marginally worthwhile considering it's $5 cost (still a rip) and the 30 to 50 minutes you are about to spend trying to get it back in. The only trick I've found is to locate a rod (like the lug nut wrench) that fits in the larger hose's hole. Use that to position it and use a long screwdriver or the like to push it back in place with the small hose still attached. The larger hose can then be reattached to it and the intake. Figure on 60 minutes of cursing and frustration the first time you change it and about 5 minutes by the tenth time. Keep it clean and pressure won't build up inside the crank case and blow your seals. Let it get dirty and nothing's safe.

    Have Fun!!


    PS I also have a, '81 245. The electronic injection makes things SO much easier!!

    From: danp@oregon.cray.com
    Subject: Re: flame trap
    To: swedishbricks@me.rochester.edu
    Date: Wed, 17 Mar 93 8:02:54 PST


    I have a '86 240DL and clean the flame trap every other oil change. It's a little tricky to get out....I do it only in daylight and reach in from the back of the engine, under the intake manifold. You can easily pry the metal baffle (about the size of a quarter and 3/8" thick) out with a knife blade. I shake it up in a jar with a small amount of gas plus spray a little carb cleaner through it to blow it out(protect your eye's). Pop it back in and reassemble. My mechanic say's not keeping up with this little chore can result in leaking seals.


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    Is there a flame trap on a intercooled turbo engine?

    From: alfred@nyquist.bellcore.com (Alfred Kwan 21342)
    Subject: Re: flame trap / flame guard info wanted.....
    To: nessa@mentor.cc.purdue.edu (Vanessa M. Cook)
    Date: Thu, 18 Mar 1993 09:29:14 -0500 (EST)
    Cc: swedishbricks@me.rochester.edu

    > Alfred Kwan 21342 writes...
    > { As far as I know, there is no flame trap on a intercooled turbo engine.
    > { Not so sure about a 240 non-intercooled turbo engine.
    > Then what have my mechanics been cleaning all these years?
    > I own a 1985 244 Turbo.

    I just check with the local Volvo parts person. He said that for the 240 Turbo, there is a filter inside the oil condensation box (part of the PCV system) but no flame trap of the non-turbo engine type.


    Date: Thu, 18 Mar 93 12:09:32 EST
    From: wiegman@orion (Herman L. N. Wiegman)
    To: jtembulk@spica.prime.com
    Subject: Re: flame trap / flame guard info wanted.....
    Cc: swedishbricks@me.rochester.edu

    There have been some good posts lately on what trap came with what kind of Volvo also how to get to them and what to expect...Here is some history and theory.

    The old B-18 motors had this small tin can on the driver's side of the block with a hose running back to the intake. The idea was that gasses inside the block, below the combustion chamber, could escape. The gasses would be introduced back into the intake where they would have a second chance at being combusted.

    The Federal gov't mandated this clean handling technique for non-combusted gasses in 1970 (I believe).

    The metal can thingy was really just a baffle or two which tended to "scape" the oil from the moist gasses. This reduced the amount of oil consumption. The baffled did not stop flame propigation well.

    A metal mesh was introduced to reduce the chances of dynamic flame travel back into the trap. The metal mesh unfortunately collects garbage and sludge. This defeats the whole purpose of the PCV system (Positive Crancase Ventilation). The internal gasses are then allowed to build-up causing gasket failure and oil leakage.

    The Turbo cars have the block vented to INTAKE side of the turbo charger. This is where the necessary vacuum is to "suck" the gasses out of the block. Somehow I think that Volvo has used a much more fancy system (as shown in Haynes manuals) which has two paths for the gasses to flow.. one during normal driving and an other during accelleration.. anyone?

    Either way, I think that some models of Volvo's do not need the flame trap because there is an other component in the path of the gas which effectively acts as a flame retarder.

    I have not inspected my '81 245 trap.. i change the oil regularly (well not all the time.. :( and drive the motor hard. I also do not have the white pasty sludge on the oil filler cap which indicates OEM spark timing. Hence I think that I am a low risk candidate for flame trap clogging.

    If you do have the sludge (white goo'y stuff) on the bottom of you oil filler cap, then you may be at higher risk of fouling your flame trap. Infrequent oil changes or short trips will also contribute to a fouled flame trap. If a car has been overheated, crusty oil deposits will also speed a clogged flame trap.

    How to get to it? Enlist a small child with strong hands, hold 'em by the ankles and drop 'em down by the intake manifold.... or take your neighbors Saws-all and cut a nice hole in your intake to get easy access to the flame trap..


    Herman L.N. Wiegman -> wiegman@orion.crd.ge.com
    General Electric - Corporate R&D, Schenectady NY
    - the Flying Dutchman in the DSP Swedish Brick -

    From: alfred@nyquist.bellcore.com (Alfred Kwan 21342)
    Subject: Re: on flametraps
    To: maj@frame.com (Michael Jue)
    Date: Thu, 17 Jun 1993 14:30:29 -0400 (EDT)
    Cc: swedishbricks@me.rochester.edu


    There are no flametraps on the later turbo bricks. The flametrap is used to prevent the hot and oily crankcase vented stuff get ignited on the intake side. On the turbo bricks, the hot and oily stuff passes through the intercooler first.

    Are there flametraps on the non-intercooled (81~83) 240s?


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    I neglected to replace the flame trap....

    From: Mark Nathanson <nathanso@umdnj.edu>
    Subject: flame trap answer
    To: swedishbricks@me.rochester.edu
    Date: Fri, 18 Jun 1993 12:24:35 -0500 (EDT)

    Well here it is from the losers mouth....

    I neglected to replace the flame trap (AKA breather) on my 240 ('86) and blew out a plug on the back of the head. Not knowing much about the trap, even though I was warned many times of the need to change it, I thought I blew a valve cover gasket. Upon removing the cover, said gasket looked good. BUT I noticed that one could see the cam turning when looking at the back of the head. Scratching my head, I thought ... did it look like this yesterday? I finally went looking for the flame trap and found it; it was clogged solid. So I poured lots of oil in the beast and off to the dealer we went.

    Now, the breather is just that, it lets excess crankcase fumes go to the intake manifold. Since this is part of the normal emission controls there is no other place for the fumes to go. So, when the breather clogs with blowby gunk it can blow almost anything. Volvo put a plug in the back of the head, much like a freeze plug in the block, just in case one of us ignores good advice. BTW, it cost 100+ to have the plug and breather replaced.

    So, do one thing this weekend. Look under the intake manifold for several hoses coming from a metal tube sticking out of the crankcase. Reach in and yank the rubber off the tube. Note that there are two hoses on my breather that go to the intake side and you do not want to yank so hard that you rip everyting out. Do not be afraid to yank though as it will come loose. I assume that you are all fairly knowledgeable and the rest will be fairly self explanatory.

    One word of caution, tis easier to remove thatn to install.


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