I have done 5 sets of front seals and one rear and it is very easy to screw one up although I never had one leak because I would remove the possible bad install and reinstall a new seal. This has happened only twice.

First do the David Hunter palm over the oil filler test with a cold engine. The suction won’t be steady but will be more pulsing. All cars have some blowby. You want the intake manifold, via the flame trap and associated plumbing to suck more blow by than what the engine produces. About every 6k, during an oil change I dump a few tablespoons of oil into the breather box and monitor how fast it drains out but I doubt this does anything to clean the buildup out.

Leaks are a little difficult to find. If it didn’t leak as much as before the seal change I’d say it is one of the seals. Another possible area is the between the seal carrier (that holds the crank and aux seals) and the oil pan gasket if at one time the carrier was removed for a seal replacement. Unless the carrier is removed properly it is easy to damage the oil pan gasket. The only proper carrier reinstall must be done with a sealant like RTV between the carrier and the oil pan gasket.
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Tom F. Couple of Volvos Mods, RainX & cup holders.

Is there anything to look for when replacing the breather box. I have 200k ('92 940) and I think it's time (flame trap & hose were already replaced)...

May be good to also check the oil breather box itself. If the box is clogged, then eventhough the PVC valve, small and large hoses are clear, the engine will not vent properly. I believe you can attach about 1/2" size hose to the box (remove the S hose) and with the engine off remove the oil filler cap and you should be able to blow through the box. I've also read that one can check for PVC system working by lifting the oil dip stick and there should be no smoke when running. Perhaps, others can confirm if the dip stick test works.
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dnvolvo '89 765T 200K - '91 245 100K

One brickboarder, I think it may have been Don Foster, took an old oil filler cap and mounted a pressure guage on it to read internal engine prankcase pressure. A tried and true check of pressure has been called the "jiggle test".

On an idling engine you simply loosen the oil filler car as if you were going to remove it but leave it in place. There should be enough negative pressure in the crankcase so that the cap is slightly sucked down and will stay in place. If there is positive pressure in the crankcase, the oil cap will bounce around or "jiggle" on its seat. The presence of the jiggle means either that the flame trap-crankcase vent system is not clear or that there is excessive blow-by.

On the newer B230 engines, the oil filler cap is a lighter design and can jiggle sometimes even with a good crankcase vent system, especially if the engine shakes a bit at idle. The test works fine on my cars with the newer cap, however. You might be able to get an older cap from a friend or a salvage yard. Some make the test by laying their hand over the oil filler opening while the engine idles. You should be able to feel a slight vacuum.

Repairman, if you find you do have positive pressure in the crankcase and you are certain that EVERY part of the flame trap system is open, you may have stuck rings from having poor oil changes in the past. I've been able to loosen stuck rings with an oil additive called Rislone. I use a quart of Rislone in place of a quart of oil at an oil change. This additive is just a concentrated detergent which allows the oil to penetrate and loosen the gunk in stuck rings. It isn't a motor flush which I don't recommend. Another way to do this is to switch to a synthetic oil and let it slowly clean the engine.

There is an additive called Auto RX which get good reviews on the net but I haven't tried it, no need to yet. good luck on fixing your leaks.

Remove oil cap with engine running, do this when it is not too hot so you don't burn your hand. Place your palm over the cover, on and off for as few seconds and feel for pressure or vacume. Either way it will be very slight. This should tell you if the flame trap is working and if you are building up pressure.
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David Hunter

ok, i gotta ask, ours is a 240, but, what's a "flame trap"? i don't like hearing things like "flame", when referring to engines, and pressures, is this something i need to know about on my '85 240 DL?? thanks, louis

RepairmanJack, did you get teh seals replaced or did you do it yourself. It seems like we are having the same questions recently. I am thinking would it be wise to have them all replaced at once. If I want to keep the car for another 10 years, why pay to have one done, when all can be done at the same time to avoid piece-mealing it. What do you think.....