Tuesday, July 20, 2010

Oil Around Spark Plug Threads?

1998 Chevy Cavalier Z24 2.4L GM Quad 4 Oil Around Spark Plugs

I found oil around all 4 of my 1998 Chevy Cavalier Z24 2.4 Litre spark plug threads.Could this be the result of a previous compression test!?

It is unusual to find oil around the spark plug threads. What does this mean? Oil on your spark plug(s) may indicate worn piston rings. worn piston rings will allow for oil to "slip" past them. a cheap diagnostic test you can perform at home is called a "leak down", or vaccum test. most auto parts stores sell leak down testers at a reasonable price. most come with instructions on how to use them. the key to reading them is the behavior of the needle in the gauge. leak down tester will confirm several problems- worn piston rings, bad valves, among others. you may also consider a compression tester. another cheap easy diagnostic procedure you can do at home and save money

That means the valve cover oil seals are leaking, and if they leak bad enough, the oil can cause ignition misfires. So when it affects the engine performance, you'll have to have the valve cover removed and new oil seals installed. we used to call them '' rocker arm covers' but they are properly called valve covers. There is a gasket between them and the top of the engine . The gaskets are worn and leaking oil.

Don't try the quick fix of just simply tightening the small bolts that are around the rim cover. This could distort the metal cover and then it might always leak. Just go out and buy new gaskets and replace them.
While you have the metal covers off take a look at the oil drain holes on either ends of the cylinder heads and make sure they are not partially closed by sludge and if so then clean the holes up.

If it's your drain plug then this is perfectly normal. If there's oil on the threads of your spark plugs then there's a problem. First of all, check to see if there's any oil on the top of the cam cover (e.g. maybe weeping out from an ill-fitting or damaged oil filler cap) that could be running into the spark plug wells. If there isn't, then the oil must be coming from inside the cylinder. The most likely reasons for this would be worn piston rings and/or warn oil control rings, worn valve stem seals or a leaking head gasket.

A compression test will show if its either the rings or the head gasket. You can also check your coolant to see if there's any oil contamination in there as that's another sign of a leaking head gasket.

To test for worn valve stem seals, take your foot off the accelerator for several seconds when going downhill, then watch for smoke when you step on the accelerator again. If you see a puff of blue smoke, you probably have bad valve stem seals.

If you have a 4 cylinder motor you most likely have a problem with the spark plug tower seals.
To replace them you must remove the valve cover and replace the valve cover gasket AND the 4 spark plug tower seals. Some valve cover gaskets come with the tower seals and others don't, so make sure you buy them if not with the gasket.

Replace the plug wires if soaked in oil as they will short out and cause a misfire. If you've had a misfire for a while it would be a good idea to change the oil. Any gas not burnt because of the misfire will dilute the oil and cause bearing failure.


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