M116 Oil Consumption, Spark Plug Fouling - PeachParts Mercedes-Benz Forum

Frank Reiner · #13 05-23-2016, 03:07 PM

Quote:

Originally Posted by JamesDean

Hi All,

The 420SEL has a bit of a drinking problem. It likes to burn a considerable amount of oil. Right now its roughly, 200 miles to a quart or so. It appears that the majority of this, if not all, is going out the #8 cylinder (driver's head, rear most cylinder).

Every weekend I end up changing the #8 spark plug and it restores the car's idle and power back to normal.

I'm only driving the 420SEL because my 300D is in paint still and my 190E has a idle/stalling problem that I am working to address.

Does anyone have any thoughts or ideas on what might be the cause of this? The next step we were planning on is a complete valve job....once funds are saved up.

The motor has 237K on it. I probably should pull the rocker cover and take a look and see if its anything obvious.....

JD:

Do the other plugs come out free of oil, or nearly so? If so, an inspection of the stem seals/valve guides of #8 may be in order. The heads on the iron block M116/117 engines, especially the earliest ones, were prone to loosening of the valve guides in the head. The heads on the aluminum block engines have been largely free of that problem, however it is a possibility. A loose guide will allow quite a bit of oil to pass thru, independent of the seal. If neither of the guides of #8 are noticeably loose, then new seals may help the problem.