So I did some research and started "fixing" it. The first suggestion that I got was that was likely the front crank seal or oil pump. Since the mileage was close to the timing belt change interval, I changed out the timing belt and water pump while I was in there. Also swapped out the PCV system, even though I had exchanged that just a few years ago and the one that came out was clean as a whistle.
Still leaking, so I spent the entire four-day Thanksgiving weekend dropping and re-sealing the oil pan. No joy, and I discovered that only two of the rubber seals in the "comprehensive" oil seal kit from Volvo actually applied to my engine.
During all this I also managed to clean up some pesky coolant leaks, so the time spent wasn't totally wasted.
Okay, back to square one. The leak appears to be only down at the lower end of the engine. The camshaft seals don't appear to be leaking, as the back sides of the camshaft sprockets are bone-dry. Then I found DIY Robert's video on how easy it is to screw up while installing the crank seal, so I ordered his installation tool and installed a second oil pump seal kit. It was very clear that I had screwed up the first installation, as the seal compression spring was completely off of the seal and riding on the crankshaft, where it left a shiny ring on the shaft. Was very careful installing the second seal with Robert's tool (which is of sublime quality, BTW), and was sure that it had gone in correctly, but we're still having leakage, albeit somewhat less than before. I'm a little worried that the seal's lip is actually riding on the part of the shaft that the spring had worked against. Next seal I install will be pressed not quite all the way in, hoping that will avoid the worn bit. Grasping at straws a bit at this point.
I'm now approaching the problem on two fronts:
- On the assumption that I've missed something, I'm gathering all the parts and tools to replace the crank seal (again), the camshaft seals and the VVT hub (this engine has intake VVT only) as well as the piston-cooling squirter valve and gasket that someone else mentioned here. I'm afraid that this is the oft-tried yet usually futile tactic of throwing parts at the problem until it goes away or I run out of money. The new VVT hub has just arrived, but I'm afraid that it may be defective. It has about 3 mm of axial play on the inner collar, but having never handled one before, I can't judge whether that's normal or not. I will be planning a trip to the local wreckers soon to see if I can pull off some sample VVT hubs and get a better feel for them. I'm loathe to pull the hub off of my engine because it seems to be working just fine.
- On the suspicion that my engine at 200,000 miles has worn to the point where the crankcase pressure under load is now great enough to overcome the capacity of the stock PCV system, thus blowing oil past the crank seal regardless of how finely the seal is installed, I will be modifying an oil cap with a pipe fitting to monitor crankcase pressure with a manometer while driving. Even though the case has decent negative pressure at idle or revving with no load, the worst leaks seem to occur after a high-speed run on the highway, which is what has me leaning more towards this hypothesis.