Help! Lm7 oil leak
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Teching In
Joined: Oct 2025
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Help! Lm7 oil leak Hello, I am new to this forum and hope I am not reposting something that’s already been discussed. This is my first time ever posting on a forum but from what I’ve read online the dudes on this one are pretty kick *** so here’s my issue. I have a 2001 Silverado With the 5.3 she’s got about 254,000 miles all stock motor when I bought it I found it to be leaking oil all down the starter, off the bell housing , the oil drain plug , all over ! Also It was misfiring at the beginning of winter as it got colder. I’m pretty new to wrenching on vehicles, but I found that the misfire was due to a vacuum leak so I changed the intake manifold gasket, and while I was in there I wanted to eliminate the high oil leak points, such as the valley pan gasket the oil pressure sensor and the camshaft position sensor o ring. Did all that and found that she’s still leaking oil so I kind of assumed rear cover or seal. Upon further inspection today when changing the spark plugs. I found that there is a pretty good amount of oil leaking past the plugs on multiple cylinders and dripping down the back of the block. Does anybody know what could be causing this? Are they not torqued properly? Are the threads on the cylinder heads going bad cylinder seven and eight seem to be the worst although cylinder six and four seem to have the same problem. I’m not totally eliminating the rear cover and seal as the culprit, but I’d like to address the amount of oil coming out of the spark plug holes. Thanks
Joined: Apr 2006
Posts: 3,891
Likes: 1,137
From: Grand Rapids, Michigan
You most certainly do not have oil coming out of your spark plug holes. If there's oil there, it's likely from your valve cover gaskets. These engines are old now, they leak everywhere. Did you replace the valve cover gaskets? If not, do that, then spray degreaser on your engine and hose it down to wash off the oil residue. Drive it and look to see where new oil is dripping from.
Thread Starter
Teching In
Joined: Oct 2025
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Yes, I have replaced the valve cover. Gaskets I will try to get a couple. Good photos after work tomorrow to post them to the thread but it looks like it’s coming right out of the spark plug And when I pull the plugs out, they’re wet. Could it be my valve stem seals?? I do start up occasionally sometimes it does sometimes it doesn’t
Joined: Apr 2006
Posts: 3,891
Likes: 1,137
From: Grand Rapids, Michigan
High mileage, valve seals probably need replaced. Are the plugs wet with oil or gas? A properly tightened plug is not going to allow oil past it, period. And an improperly tightened plug is going to blow out of the engine under the pressure of combustion. Spray the plug areas on the heads with parts cleaner and put new plugs in. You're going to have to clean everything. It's nearly impossible to trace leaks on a dirty engine.
Teching In
Joined: Aug 2024
Posts: 22
Likes: 5
From: Springfield, Arkansas
Check the gasket where the oil filter screws onto the block on the driver's side. This O-ring often leaks and sends oil running backward along the pan rail. You might also check the rear of the valve covers, as oil can drip off the very back of the heads and run down the block.
I’ve seen it many times to where the PCV get so clogged up that the engine can’t breathe correctly and crankcase pressure pushes air…it has to vent somewhere…and oil out of unsuspecting holes. Often times also in this direct issue on this thread, the cam sensor on the top rear of the engine is leaking and oil simply goes everywhere back there. I’d start with the cam sensor first. You’re going to have to go buy 8-10 cans of brake parts cleaner, and clean it all up first, to determine where the leak is originated. BPC aid flammable so be careful. I buy it by the cases. Very helpful stuff to clean new parts also.
