Leaking Oil Under the Dash Below the Instrument Cluster

Sure sign of a common problem - leak in oil pressure gauge actuator

This is very common on the older 114, 115, 107 and 123 chassis and becomming more so as these mechanical oil pressure gauges age. When the gauge starts to leak behind the instrument cluster it may take a while for you to notice (ie - dark black engine oil dripping on your foot). The leak usually starts out as a slow seepage out of the gauge. If you catch it early enough it will not make a huge mess. Watch for signs of oil dampness on the underdash panel and in and around the bottom of the instrument cluster. I have found no easy way to fix a leaking pressure guage. You could spend a lot of time messing with it and never get the leak stopped permanently. In some cases it would even require soldering (guess how much fun that is when you have oil inside the unit). Just plugging off the gauge is a dangerous proposition as you will not know what your oil pressure is and finding a suitable fitting to close the end of the line is nearly impossible.

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Problem & Solution

Common among these chassis:


If the problem is not a loose oil pressure hose fitting at the back of the gauge, then the leak is coming from the pressure chamber itself. Seem to be most common on W123 1981 to 1985 turbo diesel models. The leak may be due to the added heat of the engine oil on these engines that is weakening the soldered seal on the bi-metallic chamber tube that actuates the needle. An alternative to replacing the entire instrument is to just replace the oil pressure actuator assembly (this part is common to all years and models). New parts are currently not available so you must replace the failed part with a used unit.

We have the parts and the instructions to repair this yourself. See related products. While you have the cluster out you might want to consider changing the bulbs with new.