Oil On Spark Plug Threads

[E150GT]

Hey all,

two days ago I changed my spark plugs in my 420sel with berus from the stealership. I had changed them out in demcember but I used platinum.
When I changed them out the first time I saw just old used sparkplugs. This meaning that they looked proper with no signs of trouble as far as excessive fouling or detonation etc. Well this time around three of the eight 2 month old plugs has small amounts of oil on the threads. It didnt look like the oil was burning but was still present. I dont know what this indicates as Ive never seen this on any of my cars which have included two 200,000 mile + fords. Also at the same time these plugs were put in I did an oil change using mobil delvac 15w40 as apposed to 20w50 regular oil. Could it be an oil thing or a more serious issue? I havent noticed any oil loss since I changed the oil in december.

[MJM]

John,

Are you sure you don't have a leaking valve cover gasket?

Matthew

[E150GT]

I didnt see any oil but I will look

[david s poole]

john,if you see evidence of old oil burning at the top of the exhaust manifold it may be a sign that the valve cover gaskets have petrified and need replacing.

[juribe2]

Valve cover gasket. I had the same problem. Replaced mine 3 weeks ago.

[mbfanatic]

better recheck your Mercedes valve cover gasket for some leak or something. this might be causing the problem. better attend to this matter so that other problem might be prevented.

[dpetryk]

When all that has been checked there is another condition that will cause oil on the spark plug threads. Its oil leaking past the valve guide seals. All of my V8's had this problem of oil on the threads until I changed the seals. The oil is making its way from inside the engine to the plugs. My consumption before replacing the seals was on the order of 1 quart every 1-2k miles. After replacement zero consumption and the pluds dried up.

[E150GT]

My car doesent use any oil between changes. i think though it is slightly overfilled. My odometer dosent work so I just go three months and change the oil with some fresh dino. Im using mobil delvac 15w40 but I think I will go back to regular 20w50 as I didnt have this problem before. Maybe the slight overfilling caused the vave cover gasket to leak.

[Dee8go]

I do need to replace my valve cover gaskets. Is there anything special required to do this on my 560SEC? I don't have a torque wrench or anything other than the most basic tools.

How long should this take?

[Dee8go]

Oh, I also am wondering if there's anything else that one would commonly replace or attend to at the same time.

[rocky raccoon]

There are only four bolts holding down each of your cam covers. If they are not evenly torqued an oil leak often results. There is also the danger of stripping the threads in your aluminum head if overtightened. The torque spec is 3 to 4 Nm. Some people are mechanically "sensitive" and have a feel for such things. Those that are not would be well served with a torque wrench. The small bolts holding down your covers are best torqued using a small 1/4" drive torque wrench. A larger wrench may not be sensitive enough for the small values specified.

While the covers are off, the plastic fittings serving your cam oiler tubes are right in front of your eyes. Check them out. They may be coffee colored but that does not mean they are bad. They are easy to change and cost very little if you want to do that. With the cam covers off you can also assess the state of stretch on your cam chain and the condition of the upper chain guides and tensioner. There are plenty of posts on this forum offering help to do those things.

Time to R&R cam covers estimated at 30 minutes right side, an hour left side.

Good luck Pal. Hope to see you again at a GTG.

[Dee8go]

Thanks, Rocky. Maybe I'll do this at John's house. My mechanical abilities are very rudimentary. I can take most things apart expertly. I just have a problem with the reassembly . . ..

[Michael Pillay]

Everyone has already chimed in with the valve cover gasket. I had the same problem. The torque is not much for the bolts that secure the valve cover. Just torqued mine a few days ago. If you have the time and if the covers look bad, you could paint them while you have them of the car. Just a thought

[E150GT]

Theres also a lot of rubber hoses that could be replaced while in the general area too as I found out when I did mine. It amazing how hard the rubber gets as it ages.

[Dee8go]

These projects have a way of getting out of hand very quickly, don't they? I would like to paint the valve cdovers, but probably won't do that this time. I'll be happy to stop the oil leaks right now.