This is a 1991 Volvo 245 with 145,000 miles, automatic, California car.
BACKGROUND: In 2017 a shop replaced the timing belt, water pump, accessory belts, and the three front engine seals. Two years later in August 2019 there was a sudden and large oil leak which turned out to be mostly from the front crankshaft seal and the front seal plate. In recent BB submissions starting in October 2019, I asked questions about leaking front oil seals and learned that excess crankcase pressure can cause them to leak. Thinking back, I recalled that several years prior, the rear camshaft seal came out and fell to the ground. Naively, I just popped the old worn seal back in place. Because it was a loose fitting seal, I stuffed a mechanic's wiping rag between it and the firewall to help keep it in place. A week later, I bolted in a metal half-plate from IPD so the seal could not pop out again. That event likely was the first indication of a problem with crankcase pressure. There has been no problem or leak in that location since that time. Back to the present. In January 2020, in addition to replacing the water pump and the alternator bushings, I replaced the (Elring) camshaft seal, intermediate shaft seal, crankshaft seal, and seal plate gasket. The "glove test" shows that the engine has excessive crankcase pressure at the oil filler cap. Looking for the cause of the excess pressure, I cleaned the flame trap which was not very dirty and it was not clogged. I checked for a clog in the oil separator box by pouring mineral spirits in the hose below the flame trap. That liquid immediately ran out the drain hole in the oil pan indicating that the oil separator is not clogged. The small vacuum hose from the intake manifold to the flame trap has plenty of suction. The oil dipstick has never popped up. I've driven the car only a few hundred miles since that January repair.
CURRENT SITUATION: Two weeks ago, the leak in the front of the engine returned suddenly with a vengeance. When the engine is running, oil leaks even more than the previous time - most of the engine has a coating of oil (nice and shiny) in addition to the generous amount that drips down to the ground. It appears to be originating from the front crankshaft seal. There is a small amount of oil originating from the front cam seal area, but not sufficient to reach the ground. I plan to remove the drive belts, the timing belt, and the crank pulley to confirm the location of the leak. Meanwhile I did a compression test with the following results:
Cylinder one - 180
Cylinder two - 185
Cylinder three - 185
Cylinder four - 185
The engine was not fully warmed up for the test, nor was the throttle opened. These results would seem to indicate that "blowby" from worn piston rings is not the cause of the excessive crankcase pressure. The spark plugs had been installed about 10 years ago and were black, not tan.
There could be three reasons that I can think of to explain the front crank seal leaking again.
1. a failed seal - not likely
2. improperly inserted seal - a possibility
3. seal blown out by excessive crankcase pressure - a possibility
Though it may be worth a try, I am hesitant to just replace the front seal if it will just blow out again by crankcase pressure. I also do not want to run the risk of the rear crank seal failing from excess pressure. That would be a worse problem. In order to be sure that the new crank seal was installed correctly, I had hoped to find the Volvo approved crank seal installer but have not been able to obtain one. Although, it appears that most front seals are installed without that special tool. The pressure that can be felt putting a hand over the oil filler hole does not seem all that powerful. I have heard of 240 engines that have so much pressure that they cause the dipstick to be pushed up out of the dipstick hole. Mine never did that.
I am not sure what to do next.
QUESTIONS:
1. Based on the results of the compression check does it seem reasonable to conclude that blowby is not causing excess crankcase pressure?
2. Does the crankcase pressure increase with engine speed or load? (I ask this because I checked the engine only at idle)
3. Would a vacuum gauge yield any useful information?
4. Would a leakdown test be worthwhile to perform?
5. Does a leakdown test require special skills, or can a mediocre mechanic competently perform this? Would it be better to choose a Volvo mechanic?
6. Having eliminated the flame trap, the oil separator box, and blowby, what else might be causing the excessive crankcase pressure?
7. Other than pulling up the oil dipstick, is there a way to relieve the excess crankcase pressure by, for example, having a relief device installed somewhere in the upper part of the engine? (I would consider leaving the oil cap off temporarily to see if that might make a difference - but only if I could keep the oil from splashing out and be sure nothing would fall into the engine)
8. Does the fact that the two front crank seal leaks happened suddenly rather than gradually over time give any clue?
9. What do black spark plugs indicate? I have heard that could mean a lean mixture, which in turn can increase crankcase pressure. Any truth to that?
10. The snout of the crankshaft has two very small grooves just about where the soft part of the seal might touch. Can the soft part of the seal wear a small groove? Might that be a cause of seal failure?