I have a 1978 300D. It has developed an oil leak underneath the dash board on the drivers side. It is a dark black fluid that is slowly dripping out. I took apart the bottom of the dash board but I can't figure out where it is coming from.

If you have any suggestions it would be very appreciated.

Dark black fluid coming from under the dash, driver's side. I'd bet money the fluid is real slippery too. What it sounds like is either the oil pressure gauge, or the oil line fitting is leaking. Could also be the oil line has been rubbing on something under the dash and worn a small hole in the line, but more than likely the fitting is leaking.

To check and tighten you'll have to pull the instrument cluster to gain access. This is a W123, correct? I believe the cluster is only a pressure fit, pull outward gently. The oil pressure line fitting should be a 10mm, be sure to use two wrenches, one on the fitting and one on the gauge.

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Mike Tangas
73 280 SEL 4.5

good chance its the oil pressure gauge cos i had a similar problem. check to see if the black liquid is the same as you engine oil, cos it probably is.

i replaced the section of the instrument cluster with the oil pressure, temp and fuel gauge, to solve the problem. pretty easy job. these VDOs are expensive new, luckily i could find a used instrument cluster.