Oily plugs - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bubbastrick · 10-03-2002, 07:46 PM

Hey guys:

My truck started running rough when I was getting off the freeway this morning. When I got it home I pulled a couple of the plugs and they looked alright except for being covered in oil. The oil was all the way up the threads. I do not see how oil could get on the threads of the plugs. My question is: is there any way to find out where the oil is coming from? The only idea I had was to run a leakdown test and try to listen for air leaks.

Also how hard is it to replace the regular o-ring type valvestem seals with the positive seal umbrella type?

Thanks guys!

Fred T · 10-03-2002, 10:49 PM

To put in the umbrella seals you need to machine a spotface on the head. Best done by a machine shop. Don't know if anyone will do it with the head on the engine. I've never asked.

Did you check all of the plugs, or just two? I would guess that oil on the threads was from an external leak, valve cover. Oil on the plug tip indicates an internal leak, either stem seals or rings. A compression check will tell you if it's rings. A leakdown check will tell if you have a valve leaking, you might be able to listen for a stem seal leak with a good ear and a tube. I was trying to think of something that would foam or bubble like soapy water, but be oil based.

10-03-2002, 07:46 PM	#1
bubbastrick Registered User Join Date: Feb 2002 Location: Jacksonville, AR, USA Posts: 44	Oily plugs Hey guys: My truck started running rough when I was getting off the freeway this morning. When I got it home I pulled a couple of the plugs and they looked alright except for being covered in oil. The oil was all the way up the threads. I do not see how oil could get on the threads of the plugs. My question is: is there any way to find out where the oil is coming from? The only idea I had was to run a leakdown test and try to listen for air leaks. Also how hard is it to replace the regular o-ring type valvestem seals with the positive seal umbrella type? Thanks guys! __________________ James Strickland AS Computer Information Systems “Ignorance is a powerful tool if applied at the right time, even usually surpassing knowledge” ~E.J. Potter

10-03-2002, 10:49 PM	#2
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	To put in the umbrella seals you need to machine a spotface on the head. Best done by a machine shop. Don't know if anyone will do it with the head on the engine. I've never asked. Did you check all of the plugs, or just two? I would guess that oil on the threads was from an external leak, valve cover. Oil on the plug tip indicates an internal leak, either stem seals or rings. A compression check will tell you if it's rings. A leakdown check will tell if you have a valve leaking, you might be able to listen for a stem seal leak with a good ear and a tube. I was trying to think of something that would foam or bubble like soapy water, but be oil based. __________________ Fred There is no such thing as too much cam...just not enough engine.



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