Mercedes-Benz W210 automatic transmission control unit oil leak
Where does the oil in the W210 transmission control unit come from?
Oil rises from the transmission between the strands and the insulation of the wires when the grommet of the transmission connector leaks. There should be no oil in the connector or in the control unit. You can check by disconnecting the connector and looking for oil in it.
What must be done about the oil leak?
First repair the leak: replace the connector sleeve and new O-rings. If the nut of the sleeve spins loose because of worn threads, the conductor plate has to be replaced. Clean the connector and the control unit. After that it is worth having a workshop check the transmission fluid level and operation.
How is an oily control unit cleaned?
The unit is removed, and the inside is cleaned carefully, for example with brake cleaner, and dried thoroughly, even overnight. Solvent must not be sprayed onto the electronics. Cleaning does not always help if the oil has already damaged the circuits.
Does oil break the control unit?
Oil does not conduct electricity, so it alone does not break the unit. Harmful are water getting in with the oil and damage to the connectors caused by the oil. If the fault returns after cleaning, the oil may already have damaged the wires or the unit.