Oil on spark plug threads

[nfaj]

So I did a compression test after being paranoid about the head gasket failure that happens in s54s. I was looking to see what my compression numbers are and they were around 180psi with a variance of 1-2psi. This was also done on a warm engine.

As I took out the spark plugs, cyl 1 spark plug had a bit of oil on the threads. The spark plug well was dry as can be.

I am not understanding why there is oil on the threads with on cyl 1 especially since it had one of the highest compression reading of 182psi compared some of the cylinders which only saw 180psi. If the piston rings or valve guides are worn, this cylinder would have lower compression compared to the rest. Correct?

I was going to do the VANOS on this car but now I'm having second thoughts on how to proceed. I was wondering if anyone has any experience with similar presenting symptoms. Thanks!

[SliM3]

Typically oil in the cylinder will cause higher compression numbers if there are no ring or cylinder wall flaws (leaky valve stem seal for instance). Are you noticing blue smoke out of the exhaust? One way you can check is to remove the secondary air valve and see if any oil has accumulated.

[nfaj]

I understand that oil in the cylinder will cause higher compression numbers if piston rings are the culprit. If it were valve stem seals, compression would read low or unchanged despite the oil on cylinder walls.

Do you mean the secondary air pump? Im not sure where the secondary air valve is located on the s54.

Thanks for the input!

[Slideways]

It could be oil vapor accumulation, in which case, a tiny amount is nothing to worry about.

[Speed Monkey]

I’m guessing this is your culprit... An aged gasket that allows a bit of motor oil into the spark plug well.

[nfaj]

It could be oil vapor accumulation, in which case, a tiny amount is nothing to worry about.

I hope it is!

[nfaj]

I’m guessing this is your culprit... An aged gasket that allows a bit of motor oil into the spark plug well.

if this was my problem, wouldn't there be oil in spark plug wells or on the ceramic portion of the plug?

[nfaj]

bump!

[digger]

its not uncommon for people to lube the threads with oil which means the threads on the head will have residual oil even if you add a dry plug it gets oil on it when removed. if the oil isnt obviously on the ground strap or electrode then your probably jumping at shadows

[Arith2]

Clogged crankcase ventilation can cause pressure which can leave things a little oily. The CCV is the cheapest part so I'd start there. If there's oil in the tube down in the spark plug hole, then it's leaking up top and it's time for a VCG. Let's hope it's not your oil rings and just focus on the small stuff first, unless something is blatantly obvious. You could get one of those cheap little bluetooth cameras to visually look inside the cylinder to verify there is no oil. Cylinder 1 produces the least amount of pressure due to it's location. It could just not be scraping the oil like the other cylinders.

[mrgizmo04]

I’m guessing this is your culprit... An aged gasket that allows a bit of motor oil into the spark plug well.

If you've taken the valve cover off, there is no way for the oil to make it into the spark plug well from these gaskets, given these gaskets sit about halfway down on the outside of the tube and the tube itself protrudes quite a bit higher than the valve cover.

If oil were entering through the top of the spark plug well, top part of the coil (which makes a seal around the spark plug well) would also be oily.

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[mrgizmo04]

OP, there could be blow by from the rings, rule that out by doing a wet test, next step after that might be leak down.

I will also note that, on several occasions I have found spark plugs to be improperly torqued/loose on some engines. Most folks just do them hand tight and at first sign of resistance they stop and say "tight enough", whereas in reality they are just feeling some gunk/burnt oil on the threads, and actually taking the plug to the proper 23Nm would result in tightening it another turn or sometimes more.

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[nfaj]

Clogged crankcase ventilation can cause pressure which can leave things a little oily. The CCV is the cheapest part so I'd start there. If there's oil in the tube down in the spark plug hole, then it's leaking up top and it's time for a VCG. Let's hope it's not your oil rings and just focus on the small stuff first, unless something is blatantly obvious. You could get one of those cheap little bluetooth cameras to visually look inside the cylinder to verify there is no oil. Cylinder 1 produces the least amount of pressure due to it's location. It could just not be scraping the oil like the other cylinders.

how do i check the oil rings ? would compression be lower?

[Arith2]

Do a leak down test and see whrre the air comes out. There needs to be a tiny bit of oil in the cylinder like a few drops but no more. At TDC of every cylinder you send air through the spark plug hole. You use a leakdown guage to tell you how much air is being lost. Use your hands to see where the air is escaping. If it's the oil cap hole, which you should open, then that means rings. If it's the same cylinder valves, leaking valves. If it's a neighboring intake or exhaust port, head gasket. Make sure the valves are fully seated on the cylinder you're testing. Google a video of someone doing this to get a visual

[M3Pat]

Do a leak down test and see whrre the air comes out. There needs to be a tiny bit of oil in the cylinder like a few drops but no more. At TDC of every cylinder you send air through the spark plug hole. You use a leakdown guage to tell you how much air is being lost. Use your hands to see where the air is escaping. If it's the oil cap hole, which you should open, then that means rings. If it's the same cylinder valves, leaking valves. If it's a neighboring intake or exhaust port, head gasket. Make sure the valves are fully seated on the cylinder you're testing. Google a video of someone doing this to get a visual

+1 This is exactly what to do... and buy a big ass wrench to rotate the crank.