Several weeks back after a food stop while on a short road trip, the wife's 240 would start but not idle. It only stayed running with the accelerator depressed. It didn't run well even then. But I was able to limp the thing into a local shop and they did a compression test. They found no compression on one cylinder - I think #1. I ended up having the car towed to my own mechanic. Once things were checked out and the head removed, he reported that the head was trashed - as I understood it, one of the valve seats on the cylinder in question had somehow come loose and jammed the valve open. Hence no compression.

This was a replacement head installed by yet another mechanic some 14K miles earlier. It came off a shelf at a parts house. So no real idea of what had/had not been done to it. After only 3K miles I noted that an exhaust manifold stud on this thing had snapped already. So I purchased genuine Volvo studs and nuts and had the same mechanic replace them all. I figured that the studs were either old at the time of rebuild and not replaced or replaced with crap parts. So this head felt questionable early on, I guess.

I have looked at some of my Volvo books and I do see specs for the diameter dimension of the place in the casting where the seats are inserted. So maybe new seats were installed (who knows?) into locations that were out of spec allowing the seat to come loose? Or do seats come in various sizes and perhaps the wrong size was installed?

I guess it doesn't matter now since the car is getting yet another head rebuilt. Obviously, not the same head. But at least this is being done by a machine shop known and used by our usual mechanic who told me the old one was toast. And that shop rejected the first head he gave them so I have at least some comfort in knowing there is some level of quality control at this machine shop. But I still find it odd that a valve seat could come loose and move so far as to permit the valve to be jammed open like that.

Has anyone seen anything like this before? Thanks!