Troubleshooting Low Compression/High Leak Down
#1
Troubleshooting Low Compression/High Leak Down
Hey guys, I have an 01 Supercharged Corvette. Long story short, I had a failed oil pump and cracked block 5k ago, got a new block, machined and swapped my rotating assembly over to it. Wish I could have gone forged but the budget didn't permit at that time.
Was driving last weekend and noticed some smoke in my rear view at WOT but not at any other time while driving. Got home, pulled plugs found oil on cylinder #7. Did a compression test, that cylinder is showing barely 15 versus 180 on the rest, except cylinder 3 which showed 155. Then did a cylinder leakdown test after removing the rockers on that cylinder so the valves stay closed and that cylinder when regulated to 100psi was only retaining 20psi. Valve springs look good, valves are there at least but could be bent in a best case scenario.
I do not have any CEL or misfires, car felt fast, no noticeable driveability issues. I have HPTuners and can take a log if it would be helpful. Was going to pull the oil, cut filter open and insepect then pull the head. Should I do anything else before taking these actions? Thanks.
Was driving last weekend and noticed some smoke in my rear view at WOT but not at any other time while driving. Got home, pulled plugs found oil on cylinder #7. Did a compression test, that cylinder is showing barely 15 versus 180 on the rest, except cylinder 3 which showed 155. Then did a cylinder leakdown test after removing the rockers on that cylinder so the valves stay closed and that cylinder when regulated to 100psi was only retaining 20psi. Valve springs look good, valves are there at least but could be bent in a best case scenario.
I do not have any CEL or misfires, car felt fast, no noticeable driveability issues. I have HPTuners and can take a log if it would be helpful. Was going to pull the oil, cut filter open and insepect then pull the head. Should I do anything else before taking these actions? Thanks.
#2
You could scope the cylinder and look for damage but I would say its safe to pull the engine and replace number 7 piston. I'm sure from your description it has failed in some form(broken melted etc.