This is a 1991 Volvo 240 with 141,000 miles, automatic transmission, a California car with an EGR valve.
I am in the process of dealing with an oil leak dripping down in the front of the engine when it is running. I stripped down the front and found that the aluminum front cover plate behind the crankshaft pulley is leaking along the top. The front cover has never been removed as far as I know.
I will be taking that cover plate off and replacing the gasket. In addition, there is a small leak from the camshaft seal, and possibly the other two seals. I plan to replace all three front seals.
One of the possible reasons for an oil leak is that the crankcase pressure is too high. I want to avoid having the oil leak re-occur after doing this repair work.
Meanwhile, there are a couple of unknowns.
- Due to a mistake the mechanic made changing the timing belt and front seals three years ago, I have lost confidence in him. The leaking oil seals could possibly be due to an improper installation of the crank, cam, and intermediate shaft seals.
- When I discovered the leaking front plate cover, I also found that the two or three bolts along the top of the plate were not tight. Tightening them reduced substantially the amount of oil leaking out to just a small seepage. Why and for how long those bolts were not tight is a mystery to me. They might have not been tightened correctly at the factory. The oil leak developed rather on the quick side rather than over a period of months.
What I do not know is whether or not these leaks are a result of excess PCV pressure.
Here are the facts that suggest that there is excess pressure.
- The seal or cap on the back of the valve cover popped out several years ago.
- One or more front engine seals/gaskets is leaking
- The "glove test" shows that when the engine is at idle and a nitrile glove is placed over the oil cap, the glove inflates.
One of the possible reasons for excess pressure in the PCV system is a clogged oil box aka oil separator.

Here are the facts that suggest the separator box is not clogged.
- The engine has "only" 140,000 miles.
- The flame trap is not now and has never been clogged. The large hose going from the flame trap to the bellows is clear and not clogged. It's pretty clean in that area. The small vacuum hose originating at the nipple attached to the intake manifold and terminating at the flame trap is providing good vacuum to the flame trap area. I drilled out that hole to make it a little larger.
-The oil dipstick does not jump up from its normal position.
-When the flame trap was removed and the oil sump drained, and solvent (mineral spirits) was poured into the tube on top of the oil separator, it immediately flowed out of the open oil pan drain plug.
Because of the EGR valve, removing the oil box would be a difficult and time consuming job.
When several mechanics with some experience with 240's were asked what they would charge to remove and clean the oil separator, they each immediately asked why I would want to do such a thing. Each said they have never, or only rarely, cleaned out or changed out an oil box. One said that the dipstick popping up would be a valid indicator of excess pressure caused by a clogged oil box. They commented that a car with over 200,000 miles might possibly have this problem, but not one at 140,000 miles.
Questions:
If solvent readily runs through the oil separator and into the oil pan below, does that confirm that the box is not clogged?
The large hose running from the flame trap to the bellows. When I remove it from the bellows and place my thumb on it, I feel neither vacuum nor pressure. If I leave my thumb there, I feel vacuum building up, presumably because of the small tube connected to the intake manifold. If there were excess PCV pressure would not there be oil fumes coming out of this tube when it is disconnected from the bellows and the engine is running?
What else could account for pressure at the oil cap? Can those conditions be corrected without major engine work?