Sorry if this is a common issue, but searching for "spark plug" and "oil" comes up with a lot of posts.

Did some 160K km service on my wife's 04 MCS. Changing the spark plugs I first noticed that the auto shop gave me single prong plugs instead of the 4 prong ones that were in it.

However, the bigger issue was that the two plugs on the right (passenger) side of the vehicle had their threads covered in oil. The tips (electrodes) were dry, and the two plugs on the left side were dry.

I don't have a service manual for the car, but I'm hoping that there are some spark plug seals (gaskets) on those two plugs that might have gone. I suspect I need to change the valve cover gasket as well, and the 4 spark plug seals.

Am I correct, or is this symptomatic of something else?

Is it straight forward to change these gaskets, and is there a how-to somewhere? I've also read that BMW engines can be prone to this and it's not really that big of an issue.

Thanks for any comments!

 

Is the valve cover leaking where it would leak into the two spark plug holes that you saw oil on the threads? If so, a little oil on the threads is probably not a big deal. I would replace the valve cover gasket and the spark plugs. Check the How To section in this forum for instructions.

 

Thanks! Sorry I couldn't find the how-to for the gaskets.

I should probably just order the entire gasket set.

 

Here is a link to a valve cover gasket How To that was in the Gen 1 How To section:
https://www.northamericanmotoring.co...er-gasket.html
It looks pretty detailed with many photos.

 

I wrote that how-to! I must say, having done this job, that I don't think it could be faulty spark-plug gaskets that allowed oil to get onto your spark-plug threads. The spark-plug wells extend beyond the top of the valve cover - pull a plug wire, and you'll see the steel tube sticking out the top - so there's no way oil could splash off the valve train down into the well. In other words, if a spark-plug gasket were leaking, it would allow oil out the top onto the valve cover, perhaps, or even around the seat for your plug wire, but it would really have to take a labyrinthine course to get down into the well itself.

I think you have other issues. Are you sure it's oil - not antiseize, or something like that? Maybe do a compression test and find out if oil could be making it past the piston skirt?

Also, I have always found my engine to run smoother with the multi-electrode-ground plugs than with SEGs like Iridiums, etc. You may have different results, but I like the OEM-spec plugs.