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Oil around spark plug holes, this mean anything?


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#1 Guest_bastaad525_*

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Posted 21 May 2005 - 11:44 PM

L28ET motor. I noticed today there was a bit of oil around the #4 spark plug hole. It seems to be originating from the hole itself, as there's no trail or trace of leak from above that point. The oil 'splotch' was spread about about 1" in each direction from the spark plug itself, as well as some had dribbled down onto the block.

I checked the spark plug and it was torqued to spec. I removed the plug, and there was a bit of oil pooled up at the bottom edge of the hole, as well as some oil around the threads of the plug and the washer. However the tip of the spark plug was clean, well not CLEAN like lean clean, but a nice light tannish/greyish color as it's supposed to be, no sign of oil on the business end of the plug.

So what does this mean, if anything? The motor is rebuilt top to bottom, and runs fine. I don't seem to be burning oil, I rarely have to top the oil off at all and I get no smoke from the exhaust, and again the spark plug tips were dry... so where on earth would this oil be coming from?

#2 dapiper

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Posted 22 May 2005 - 01:50 PM

Your rings are shot. Engine will run for quite a while like this...years, but plug threads will be wet with oil and octane reqmts will rise.
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#3 Guest_ON3GO_*

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Posted 22 May 2005 - 01:55 PM

when that happened to my L28ET it was my rings that were gone.
do a compression test.
maybe even a leak down test..

mike

#4 dapiper

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Posted 22 May 2005 - 02:57 PM

Compr and leakdown will test OK and repl valve stem seals will not cure either. I endured this problem for years and although still had 2-3 % leakdown and 150 psi compr on 8:1 CR the plug thread remained wet. Machinist said rings had lost all tension.
'77 Custom Turbo
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#5 wheelman

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Posted 22 May 2005 - 03:32 PM

Bastaad,
Didn't you just have the thing rebuilt not long ago? I'd clean it off and watch it for a while before getting worried. If it returns then there is a problem otherwise it might have been some oil that was spilled the last time you changed it. The washer and threads can pickup oil from the "pool" when you remove the plug.
Might be worth doing a compression and leak down test just to satisfy yourself though.

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#6 Afshin

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Posted 22 May 2005 - 04:22 PM

I'm with wheelman on this one and would not worry yet. clean the plugs, clean out all the oil...I have had the same thing happen on different plugs at different times and it never happened again. After all the oil is on the outside of the engine and if the plug was not falling off, how would the oil pass thru the thread and just pool there when 1000psi of peak combustion pressure can't leak thru? At least that's my thinking on it. Am I missing something in the failing rings theory?
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#7 Nismo280zEd

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Posted 22 May 2005 - 04:39 PM

I had this same problem on my 280z motor... turned out it was the crush seals on the spark plugs... They had been tightend and loosened too many times... new set of spark plugs and I never had the problem again.

-Ed

Also if you run synthetic (assuming you do) you'll have aslight leak around the valve cover seal... just nature. The oil is doing what it was designed to do... get into every little knoock and cranny.

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#8 Tony D

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Posted 22 May 2005 - 05:13 PM

These mystery leaks. Anyone running a fully-functioning PVC system?

My experience has been "nuisance leaks" increase when those little K&N filters start appearing on the valve cover...

#9 Tim240z

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Posted 22 May 2005 - 05:15 PM

I vote for the valve cover gasket. Clean everything around that area until spotless and shiney. Then watch for evidence of oil. A piece of white tissue paper or napkin pressed over the area between the valve cover and plug will tell you any sign of oil.
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#10 dapiper

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Posted 22 May 2005 - 05:38 PM

If recent rebuild, may need time to allow rings to seat. Bores need to be perfectly round for rings to seat. Did u use torque plate? Chrome rings less forgiving than moly. Use non-deterg oil for break-in.

If just one cyl, then maybe oil seal. Chk to see if seal remains on guide. Sometimes they pop-off and ride the stem. L28ET seals are shorter and will not stay put on N42 head guides.
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#11 Guest_bastaad525_*

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Posted 22 May 2005 - 06:01 PM

yeah the motor is fully rebuilt now (though I didn't rebuild the whole thing at once but that's a whole 'nuther story!). The rings are new, compression is good. When my rings were bad before the rebuild, there was no mistaking it, the spark plug tips were wet with oil, and I was getting quite a bit of smoke from the exhaust (though compression still showed fine on all cylinders). But this time there is NO smoke or oil on the plug tips. Not sure how many miles off the top of my head since the rebuild but it's somewhere in the 5-10k range, well past the break in period.

I am running synthetic oil (Mobil 1). Valve cover gasket was replaced recently as well (felpro gasket) and it is BONE dry all the way around. It's all very clean so a leak there would be immediately apparent. It's the #4 plug so I don't even think it could be spillage from when I've topped off the oil.

Yes I'm running K&N breathers on the valve cover and block in place of a PCV system, Tony D why would this cause oil to seep thru my spark plug holes?

The theory about the crush washers on the spark plugs being worn out is a good one, I have removed and replaced these plugs quite a few times as I was experimenting with enlarging the plug gap when I installed my MSD ignition... I'll get a new set of plugs ASAP.

Thanks for the tips guys, I've cleaned the area and will keep an eye on it... still kinda worried as the oil did look fresh, but it was hard to tell. Well not much I can do about it anyways even if the rings ARE somehow bad again... if worse comes to worse I'll check the valve stem seals and I do have a set of the Viton brown seals maybe I'll replace them just for the heck of it though the seals on there now are new (the black ones). Well the motor runs great anyways and as I said no smoking, and uses almost no oil, so I doubt the engine is 'bad'. I'll see if any oil builds up around there again.....




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