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I have a 1992 chevy 5.7 liter v8 4×4 it the burns 1 quart per 100 miles. The engine has 120,000 miles. The knock sensor went out. It was replaced. The head gasket was leaking so it was replaced. The spark plugs are not fouled up. It does not miss so it seems not to be piston rings. How do I tell if it’s valvery seals. I have watched videos and see you can do it with the head on. Other than compression test is there any other test I can do to diagnose the isssue. And it only smokes when you step on it hard. After a cold start it leaves black oil on the garage floor. Thanks in advance. Any help would be appreciated.
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Because it actually LEAKS OIL OUT? Judging from dark oil stains left on the floor? And pretty bad to that matter? I bet you, it’s oil pan gasket and rear main seal.
Aha. So no oil stains under the drive train?
Somehow I think you have more of condensate/soot mix coming out of exhaust, than oil itself.
Well, if she burps grey smoke when under load, it’s definitely internal oil leak into exhaust from CC-s.
Your cat will go next soon, it can not stand abuse like this for long.
I’d say, best bet is to do major overhaul, starting with engine head.
See, compression test will show you 2 things:
– if rings are Ok
– if valves are seated properly and not burnt out.
Should rings be bad, it’d be burning oil as in – turning it black,due to blow by of exhaust gasses into crankcase. But it normally does not chug on oil at such speed.
Hence, you either have leak somewhere or, oil drips liberally into combustion chambers and burns out there.
Check spark plugs? Are they covered in black sooty residue? Then it’s into cc leak either around valve stem seals, or from head gasket. Yes, I saw you haed gasket done. Was head resurfaced same time?If the catalytic converter is still there, and working, you probably won’t see a whole lot of smoke from the burning oil, as most of it will wind up in the converter. That will soon plug up from all the burned oil, and then performance, and fuel economy will suffer tremendously.
If it actually burns the oil and is not leaking I would say that it has a serious internal problem to burn 1 qt in 100 miles.
Many people hope that it’s just valve seals, in my experience, it’s often much more than that. A worn out engine is just that, worn out. Based on your description I’d say that’s what you’re probably dealing with. More info on these issues here.
http://www.ericthecarguy.com/faq/finding-and-fixing-leaks
Good luck and keep us posted.
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