Hello Fellow Mercedes frinds,

A week ago my engine started to have a tapping noise. It is not very loud but its quite irritating. The frequency is tha same as the firing of one cylinder why I assumed it was a valve or a conrod bearing.

I added oil because it was slightly low but this did nothing to the noise which is normally the case if it were a valve slapping noise. I used my stethoscope and it is clear that the noise is coming from the front of the right hand cylinder bank. I changed the spark plugs and all the plugs on the right side was white while the plugs on the left side was black.

After that I opened the oil fill hole and listened (on the right rocker cover) but there was no increase in the tapping noise.

After that i started to pull the spark plug wires to see if that did anything because if it was a conrod bearing i assumed that the noise would go away or be reduced if there were no combustion in that cylinder. No change to the noise at all.

I´m now a bit confused and need Your help. What can give a noise like this if it´s not the valves or the conrod? Why is the right bank running leaner than the left? Can the timing chain give a noise like that?

And most of all what can I do about these problems.

The idle is also a bit rough but have been so since a bought this car a couple of months ago. Its a Euro spec car so there are no catalytic converter.

Please help and many thanks in advance.

Mikael Westerberg
1984 500 SEL
Vanersborg, Sweden