The wife's Clubman started leaking coolant last week from the back side of the engine. Had a mechanic check it out and he said the leak was on the thermostat housing. He replaced the housing and a hose, not sure which hose. When the wife brought the car home she handed my a section of plastic duct with some bends in it and a 90 duct elbow. I asked her "What this" and she said she didn't know. Said it was inside the car and assumed it was an old part that got replaced and the mechanic just returned. It looked like an air duct to me which shouldn't have been part of a thermostat housing replacement so I started looking around under the hood to see if I could find where something was missing. Sure enough I found that the duct was the fresh (cold) air supply duct the runs from the front of the car next to the grill, back to the air filter box. I told her to take the car back to the mechanic and tell him to finish his job but finally decided that is would just be easier in the long run to put it back in myself. To make a long story short it took about an hour to get take the air filter housing apart and move things around to get the duct reinstalled. In the process I found where the air filter element itself was not even the correct filter for the car. Anyway my wife cranked up the car the next morning to go to work and when she back out I saw a small puddle of coolant on the floor. I stopped her and looked under the car but didn't see anything leaking. I made sure the reservoir was topped off and told her to check for leaks when she go to work which was about 15 miles away. Sure enough she called me said there was a lot of coolant dripping from behind the engine again. She also said the lamp that looks like a little engine came on and stayed on while she was driving to work. I had to run to town so I went by to look at her car and saw where coolant had been leaking but had stopped. Reservoir level was down a little but not much. Mechanics shop was closed that day so I added some fluid and told her I thought it was safe to drive it home. When she got home there was no leaking but she did did make a comment that the electric engine fan was staying on for a longer time than it normally did. The fan finally shut off and I let the car sit for a few hours but no leaking appeared. I decided to us a empty the reservoir and refill it with clean coolant and distilled water so that I could check to see if coolant was moving in and out of the reservoir. We then took a 10 mile drive and I check for leaks at a couple of locations along the way but no leaking. It was a cool day yerterday, about 72 degrees. When we stopped the car after 10 miles I shut the engine down and the fan, which was already running, continued to run for about 5 minutes. Started the car and make the 10 mile drive home. Got home no leaks but the fan stayed on for 7 minutes after the engine was shut off. Started up the engine again and within 5 or so seconds the fan kick on again and stayed on for about 5 minutes after the engine was shut off. Like I said, it wasn't a real warm day and there didn't seem to be a lot of heat coming up off the engine and the engine overheat warning light has never come ON. This morning I checked the car after it had all night to sit and cool down. No leak but I noticed the coolant level in the reservoir had risen about 1/2". I expected the level to go down after the car had a chance to sit overnight and cool down.

So are there any MC mechanical guys out there that can explain the leaking then no leaking, the fan staying on longer and why the fluid level went up and not down in the reservoir? I have some auto savvy and this on is leaving me scratching my head. Would appreciate any knowledgeable comments.

 

Only things I came think of are:

Air in the system.. As for the leak/no leak deal.. I'm not sure unless it was some sort of passage that held coolant after it had spilled out..?

 

Just started up the car. Has been sitting in the garage all night and engine was cool. The minute the car was started, the fan came on immediately. Ran the car for about two minutes and turned it off. Fan kept running for about 5 minutes. I can't for the life of me understand when the engine was cool to begin with, why the fan would have kicked on.????

 

Was the thermostat's temperature sensor replaced too? (Normally it is; the thermostat comes from Mini/BMW with it.) the inconsistent behavior is similar to when my thermostat temperature sensor failed, modulo the leaks which I did not have.

Really puzzling case. Good luck!

 

Which engine do you have and how many miles?
You need the codes pulled with a Mini/BMW specific code reader. Do you have the little Yellow triangle light on in your speedometer cluster? Does the shop that did the work specialize in Mini's? From your description of the work my impression is the shop is inexperienced with Mini's. There are areas on the top of the transmission that can hold coolant. If the shop did a poor job of cleaning up after the work then this coolant will blow back and then drip. A quality thermostat housing will come with a new coolant temperature sensor. If they reused your old one then it could be suspect which could cause the fan to run erratic. Also if the shop is inexperienced with Mini's they may not have bled the system of air properly. The process can be tricky if you don't know how to do it.

Find out if the new housing came with a new temp sensor.
Has your water pump ever been repalced

 

My car had the fan speed issue which was an issue with the temp sensor in the thermostat housing. The latest N18 thermostat housing revision is an all new design which requires a small wiring harness adapter because the sensor is in a different location.

My car never overheated nor did it leak or boil it's fluid. Once the temp sensor was replaced the car runs great. No issues.

Sounds like you need to check the invoice and make sure you have the latest PN installed. And make sure they used the correct amount of anti-freeze.

My car, which has an N18, threw a fault code 348E.
These are the PNs:
11-53-7-647-751 thermostat housing (115040)
12-51-8-611-289 thermostat adapter (12999951)

They also added in 2liters of anti-freeze.