Oil on sparkplug threads
Thread Starter
Joined: Mar 2003
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From: Hamilton Ontario
Oil on sparkplug threads so Im swapping out the plugs this morning and all the plugs have oil on the threads. The valve cover isn't leading. The plugs themselves look good, anyone seen this before or have any idea what it is?
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
Every time I've had oil on spark plug threads (only the threads, not the tip), it has always been from a weeping valve cover gasket.
If the tip/electrode is oil fouled, then you have a different problem.
If the tip/electrode is oil fouled, then you have a different problem.
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
Any loss of oil measurable on the dipstick?
Typically, leaking valve seals will allow a bit of oil into the combustion chamber after engine shutdown, and then you'll get a puff of smoke on start-up when this is burned off. I've had this before, got some pretty big oil puffs from the exhaust on start-up, but it was never enough to cause oil deposits all the way up the threads of the plugs (or foul the tips, but yours doesn't seem to have that issue either).
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Joined: Jun 2009
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From: Tulsa, OK
You won't necessarily feel anything under the valve covers, as it accumulates in the spark plug wells over time, not over night. Bad stem seals will not do this.
Thread Starter
Joined: Mar 2003
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From: Hamilton Ontario
The plugs as I pulled them out were wet with oil and the same all through the motor. The car has smoked at wot but I though this was a rich condition from the tune. I will see better tonight when it goes on the dyno.
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From: Schiller Park, ILL Member: #317
If you are seeing smoke from the exhaust during WOT and it isn't due to overly rich A/F or carbon build-up, then I'd look beyond valve seals.
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When my valve seals were bad on my 436ci......I wouldn't get that puff at start-up......I did have wet raw oil on all of my spark plug threads though......also, when I went WOT from a steady cruising speed I would leave an initial HUGE blue-grey cloud of smoke.....then as I stayed on the throttle that cloud would slowly, over about 3-4 seconds clear up and it would be clear as I continued to accelerate.
When I hit the throttle that sudden decrease of pressure would suck oil through the leaky valve seals from the oil under the valve covers....going through my cylinders and giving me that huge initial cloud of smoke. As the pressure started to stabilize that cloud would clear up.
I removed the heads and had a valve job done on both heads.....problem solved.
I think if the valve seal leaks were really bad....you will get the start-up puff of smoke too.......as some people do.
.
Last edited by LS6427; Aug 13, 2014 at 01:26 PM.