I'm guessing it's a valve...
 

So i put a manual boost controller on my 96 850 turbo wagon and had it set for 10psi and was driving down the highway making sure it didn't go past 10 (autometer gauge) and when i came to a stop it was missing. Got the OBDII scanner out of the glove box and sure enough it was a miss on #3. No smoke and no compression on #3. So my educated guess is a problem with an exhaust valve.

I'll be pulling the head this afternoon and will report later whether I was right or not.

And sure enough one exhaust valve on number three cylinder has a triangle shaped piece missing from it. I'm lucky it didn't drop a valve and there is no damage to the cylinder or piston. The cylinder still has good cross hatch in it and there's no ridge at the top. These Volvos are amazing, this one has 218,000 on it and everything looks good. It only took about 2 hours to get the head off! The real bummer is that one of the head bolts broke off below the deck surface about 1".

I will try and post some photos and if I'm too retarded for that I'll put a link to my flickr account.

So I'm wondering if I should replace all the exhaust valves or just the ones that look bad? And does anyone know a tried and true method of getting broken head bolts out of Volvos? I'm thinking about making a drill bushing and going about it that way.

fun!

Ok, here are some pics of the damage and the car.

http://www.flickr.com/photos/rosstho...7623832834394/

Fun indeed!! Getting broken bolts/studs extracted is more of an art than a science! Never heard the "drill bushing" method here's what I do:

1. Starting with small titanium drill, drill a hole as centered as possible in the center of the bolt; preferably all the way thru if you can. Be careful! If you get into aluminum, stop immediately! Keep going up in drill size until you get a decent sized EZ-Out in there.
2. Get some anti seize lube in there thru the hole. With a pin drift, slightly smaller in diameter than the bolt, but bigger than the hole you drilled, rap the end of the bolt with the pin drift and hammer. Idea is to break the frozen threads loose.
3. Up to your discretion but at this point I like to apply heat to the aluminum around the seized bolt; steel and alum has much different expansion rates helping to break the frozen threads loose.
4. Try the EZ-Out; work it back and forth until threads are loose. Don't break the EZ-out!!
5. Good luck!

Oh yeah, while I was in there, I would do a full valve job!

Thanks for the input, that is the method I usually use but using a drill bushing keeps the bit centered especially in this case where the bolt is not broken off flat. It might be a few days before I even mess with it as thankfully it's not my daily driver. I'm definitely doing a full valve job and I'm thinking about replacing all of the exhaust valves.