Last winter the rear main seal started leaking immediately after being in the shop for a brake caliper replacement. What's so frustrating is that knowing the propensity for high-mileage volvos to leak, I was pleased that this one was bone-dry when I bought it last September. Now it's leaving a tablespoon of oil on the ground after any short drive. It has 170,000 miles on it.

I'm just trying to figure out what could have caused the sudden development of this leak.

The circumstances were this: Outside temperature was about 5º F, drove 2 miles to the shop, parked it inside. They did the repair, I picked it up that evening, went to dinner, and when I parked it in the garage, I noticed a spot on the driveway where I stopped to let out my passenger. (No, the spot was oil, not the passenger ...)

I took it back to the shop in the morning, they put it on the lift with engine running, and we all watched as oil seeped out of a rectangular weep hole. The owner of the shop told me it was the rear main seal. He works on many Volvos, so I take his word for it. There is another gasket at the driver side that appears relatively new, by the way.

When the car was back on the ground, the mechanic (a younger guy) checked the oil, saw it was low, and asked if he should top it up. The owner wisely said no. At some point earlier, the owner had asked the mechanic if he had added any oil, and the guy said no then, but I have doubts. I was surprised at the mechanic's question, because that would be a rookie mistake to add oil to an engine that had just been shut down. This shop changes my oil every 3,000 miles, and they have been the only ones to do so since I got the car.

When I checked for myself later, the oil was over-filled. Knowing that it's leaking, I let it be.

My question is, is there anything in particular that could have caused this - going from very cold outside to warm shop, over-filling the oil - or was it just due to fail because of the high mileage? I've already discussed it with the shop owner, and he does not think over-filling the oil could cause a seal failure like this.

It is in general a good shop - they service the exotics in addition to Volvos (from MG to DeLorean to 1932 Marmon rebuilt over 9 years) - and I've been to most of the other shops in town. I don't want to switch shops again.

Anybody have some insight to offer?
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Charles Grammer - '93 245 (140K), '96 850 (170K)

Check that the flame trap and the crankcase ventilation lines are not clogged.
That will cause overpressure to build up inside the engine.. Try a search for pcv or flame trap in this forum, there are a lot of postings. Bay13 have instructions how to clean the flame trap

Hmmm ... hope emerges ... I am planning to catch up my regular maintenance and replacing the flame trap is on the list. In fact I have the parts already from FCP Groton. I was also planning on checking the PCV, but I see they are expensive to replace, and presumably not something to be done "just because". Not sure what to look for in checking, although I have both Chiltons and Haynes. I'll see what Bay13 has on it.

Thanks.
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Charles Grammer - '93 245 (140K), '96 850 (170K)