I just bought a 2007 Mini Cooper Base (no turbo) with a manual tranny. It has registered code P128B. It was cleared once but came back. I hooked it up to an expensive Snap-On scanner and drove the car for 3 miles with the AC on (70 degrees F ambient). I monitored the coolant temp with the scanner during this trip, and while idling for a couple minutes, and the highest it reached is 170 degrees F. I used a laser thermometer and checked temps around the engine while running after this drive. The ECT was showing right at 170, in agreement with the scanner. The top radiator hose was around 130-150. The Tstat housing was about 140. The hottest spot I could find on the head was about 207. I assume my thermostat is stuck open as I should be up to around 200F after a drive like that. However, is it possible that the thermostat is being opened by the electronic solenoid valve? I do not have code P0597. Also, my fan seems to be running way more than it should. Someone told me that might be a failsafe built into the ECU to protect the engine in the case of a cooling system fault.

I think I should just put in a thermostat/thermostat housing. I found cheap ones for about $35 What do you think?

 

More information. The used car dealer from whom I bought the car said the ECT sensor in the head was unplugged when he got the car. He plugged it in and cleared the code. It passed a smog check after that. This code came on after I had the car for a few days. I don't mind replacing the thermostat, but I don't want to just throw parts at it. I don't know if I have a good housing or an aftermarket one. My housing does have a square brown sensor on top and I think I can feel another sensor on the bottom.

 

No one has responded yet, but I suppose it's because this is a topic that has been discussed much in the past.

After doing some more reading online (mostly here), I decided to look into the electrical connections. I was going to try to trace the ECT yellow and white wires back to the ECU and check ground. Ground checked out, but while handling the connector it literally crumbled in my hands. I went to the JY to try to find one. I could not find one that was identical (I even looked at a couple late 90's BMWs) but I found several that looked similar. I soldered one in that seemed closest. I think it was from a Suzuki.

My latest codes are P115C (MAF), P112B and P0117. I think the last two make sense with a bad ECT connection as I think one means unexpected high temp and the other means unexpected low temp.

My code reader won't communicate with this car, so I'm trying to get by borrowing them until my cheap eBay one arrives.

Any ideas are welcome!

Any ideas are welcome!

 

 

Above is my digital water temp gauge. It also reads DTC codes, fuel trim, vehicle speed and a few other things. This helped me correct my DTC codes. Now that I have a better idea of how the cooling system works, I think it's scary as hell driving around without a coolant temperature gauge on these cars. I had a bad ECT sensor connector. I ordered one from an as yet unnamed reputable OEM parts distributor. The wires I was sent did not fit inside the plug. I soldered in a junkyard connector from a GM car. I had to modify it to get it to fit the socket. Now my gauge reads constantly and my CEL went off after a long drive. This is what I believe to be the case about how the system works: Incidentally, I am very happy with this little $36 gauge. I was able to mount it with one of the Tach screws, using one of a longer length. It turns on and shuts off automatically when I use the car (most of the time!).

The thermostat opens at around 105 or 106 degrees Celsius, and will stay open for a while after climbing a hill (I just did an 80 mile trip with 8000 total feet of elevation change). At those times the ECT will drop into the mid 80s. In traffic the temp will stay right around 104 to 106. The cooling fan will not come on until about 106 or maybe even 107. In the absence of a valid signal from the ECT sensor, the ECU will run the cooling fan constantly, and will run for several minutes after shut down, even if you've only run the car for a few seconds. I believe there is only one ECT sensor and that a Mini will let you cook it's engine with no warning. A car will run with a bad or no ECT sensor. The ECU will hold open the thermostat and run the fan, but you could keep right on driving until the engine siezes. Correct me if I'm wrong on this but my car ran great for a week and a half with a bad connector sending no signal at all to the ECU. The cylinder head temps were around 170 farenheit according to a laser temp gun, aka the thermostat was held open.

 

I'll post my experience I have about the same car 1 year newer, 2008 Hatchback with the 6spd manual. About 16 months ago I had issues with my thermostat which was about a year or so after buying it as my first cooper.

I use Torque Pro for my gauges on my android phone for many years on many vehicles (11 Ram Diesel, 03 Olds Alero, 1999 Grand Cherokee, 2 Coopers a 08 MC and a 09 MCS(R55)) ODB2 bluetooth in all, the only headache is changing the ODB2 device in the app when I change vehicles.

Anyway on to the temperature issues, mine started to give the codes which ones I don't remember but the temp was dropping from when I first started driving it, BTW it should run around 215-220 degrees F (with one caveat it will run about 30 degrees F cooler when A/C in on), mine was down to about 105 on the way to work one cold January morning so I also assumed the thermostat was the culprit. I changed my thermostat with one off of Amazon paid about $80us for it. Biggest thing I wanted to point out is the difference with A/C on it will greatly affect the temp of the engine.