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I've just completed a careful head removal. Getting to those exhaust nuts and bolts turned out to be a real challenge, but I finally finished the task. The lower water pipe bolt was also a challenge in working blind.
I carefully levered the head off and transferred it to a flat cardboard box. I took a look at the valve surfaces and they all look pretty good. But I think I know why.
There's a sticker on the computer box stating that the volvo dealer replaced the timing belt at 172,000 miles. I'm at 220k now, which should mean that that I have another 20k-30k miles on this belt.
Upon removing the head and starting to clean out the combustion chambers I noticed that there are a pair of deep marks on the frontward side of all five pistons. They are pretty clearly valve impact marks.
Checking the valves again, I can see nothing to suggest that *these* valves hit those pistons. My working theory is that the original owner let the belt snap and paid a pretty penny to put on a new head - that, or the car got a complete valve job.
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Head gasket failure is not obvious, but I see some evidence of trouble.
All the cylinders were carbonized on the top, but #3 came *really* clean with minimal efforts. The #5 exhaust manifold port has recent internal surface rust formation, all others were clean. #3 piston had some weird black carbon throughout. It's hard to describe, but was quite unlike the usual carbon build up one finds in a cylinder. There were also some places of odd build-up under the gasket.
Several of the exhaust manifold gaskets had broken also. I had to fish one little fragment out of the exhaust manifold.
I'll load up some pictures soon.
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