I just got Fenimore back yesterday from getting a leak fixed from oil pump solenoid. This is the second time. I talked to the service manager about this for a little while, because I wanted to understand what was going on.

The problem is that the solenoid leaks oil, and it starts wicking up along the wire (through capillary action) and can eventually make its way to the ECU. The wire insulation will start to degrade when it gets contaminated with oil, and the ECU will start having problems when the oil gets inside of it.

There have been a couple of fixes for this problem over the years. I've hit two so far.

The earlier fix was to replace the solenoid, and replace the wiring harness. This harness had a different connector on it; instead of a single plug for all four wires that plug into the thermostat housing, there were two separate two-wire plugs. This required replacing the T-stat housing with an older version, so that was swapped out as well.

It turns out that the replacement solenoids are not immune to leaking either. This puts us right back where we were. Instead of replacing the solenoid again, MINI has come up with a new wiring harness that has a section filled with epoxy, to keep the oil from leaking up through there. It has somewhat different connectors for the T-stat housing as well, so the housing gets replaced with a brand-new version.

I do not know when the current wiring and t-stat housing were first used. Probably after two years ago, which is when the first leak happened.

I am not sure if this current fix (epoxy in the wiring harness???) is a permanent fix or not. Hopefully it will be; we shall have to see.

 

Had the oil pump solenoid and wiring harness replaced on my 2011 R56S a couple months ago under factory warranty. The epoxy thing sounds like a band-aid to keep the oil from fouling up the harness if the solenoid leaks again. Why not just make a solenoid that does not leak oil? Right?

I will be keeping an eye on my solenoid for leaks, definitely!