Ragnarok69 |
10-14-2018 08:51 PM |
Potentially bad piston/rings
Some back story: 09 Cobalt SS/TC. Its been laid up since last year, haven't had much time to work on it. Did a compression test initially (cant recall #'s but I knew 2 and 3 were still good and 1 and 4 were lacking) So I eventually pulled the head off found a handful of problems. Lapped the valves, didn't see any damage to them outside of the coating of crap around where they seal/seat. Didn't notice any head damage. had a lot of oil below the head, saw that the headgasket had basically taken a dump. Checked the injector seals for damage, Visually inspected the sleeve walls, didn't see any signs of scoring or cracks. At this point I should have gone further and removed the pistons and inspected the rings, rods etc, but after finding stuff like the coatings on the valves and the headgasket issue I figured I were in the clear and decided to reassemble. Car seemed good for a couple of hours idling, and then eventually sounded like she was falling on her face again. Tried to drive her around the block and would get some blue tinted smoke out the exhaust.
Waited a couple days intermittently starting it, while waiting for a leakdown tester that I ordered to come in. and this is what I found this morning doing a compression test first. Cylinders 1-4 in psi, 60,180,185,135. Did the leakdown test with instructions I found off a thread on here somewhere. And the loss/leakage %'s if I did my math right were as follows 73.5%, 3%, 2%, 35%. All the cylinders had some air coming out of the oil dipstick (As I know the rings aren't a perfect seal), but cylinders 1 and 4 sounded like they were losing air from the valve cover to the compressor side of the turbocharger, and after pressurizing the cylinders (one at a time of course) If i opened the oil fill cap you would hear the air abruptly leave those 2 in particular (cylinder 3 also did this but it was ever so slight in comparison). None of the cylinders showed signs of air leaking into the coolant or bubbling in the reservoir. I didn't hear or notice any air hissing out of either the intake manifold or the exhaust manifold. Should I have checked anywhere else to better determine the cause of the compression loss. Or should I at this point assume that its quite possibly my pisons/rings or something close to that vicinity. Or is there another place I should look while doing a leakdown test. Any information would be greatly appreciated. ;)
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