pics of block and head pls. also check to make sure the valves are closing properly. might be a piece of junk/old gasket/carbon buildup making a valve leak?
Blew my 7M, what should I do?
- Thread starter jake8790
- Start date
Mine did the same thing one time. I was confused too until I disassembled the shortblock and found this.
gtsfirefighter
SM Expert on White trash
Pull the engine yourself and take it to a reputable machine shop and have the short block rebuilt and the surfaces machined. Either have the head rebuilt (best choice) or have it pressure tested and resurfaced. I would never trust buying a supposedly built or rebuilt engine from anyone unless I knew the shop that did it. My philosphy is that all used 7M's have a BHG or rod knock. Good luck and keep it 7M! 
When I had issues out of my 7m, I lost compression on 3 cylinders. After taking the head off my head gasket looked fine and when I tore the short block apart, I checked the pistons and they were fine also. The problem wasn't revealed until the I checked the head. Turns out it was cracked. I re-assembled my short block, and got another head, now its good as new. Good luck on rebuilding.
Yeah, keep track of where everything goes. Set aside your piston/rod/bearings and label which cylinder it came out of. Do not just throw parts around and lose track of where it all went. Just incase you do find out it's not the bottom end you clean and put everything back as long as they were in spec.
Of course start with the cylinder bore that lost compression.
Of course start with the cylinder bore that lost compression.
I've read broken rings like mine are caused by worn cylinder walls which wear more at the top of the bore from more cylinder pressure against the rings. As the rings expand and contract along the uneven bore they eventually fatigue and break. Does this sound right? It makes sense to me, my engine had almost 300K on it.