I have a base 2011 Clubman that recently developed a thermostat issue. It started a couple of weeks ago when the check engine light came on. I read the codes with my scanner and they are P0597 & P0598, which indicates low voltage/no current from the temperature sensor. I ordered a new thermostat housing and installed it. The first issue is the new housing has two sensors on it (the original only has one) and came with a 'Y' wiring harness adapter. there were no instructions as to which end of the 'Y' harness adapter went to which sensor on the new housing. So, I plugged it in to the sensor that seemed appropriate. I refilled the coolant via the reservoir, started the engine and the check engine light is still there ( I had cleared the error codes prior). After a few minutes the yellow coolant temperature warning light came on, at which time I shut off the engine. Thinking that I had plugged the 'Y' adapter harness into the wrong sensor on the new housing, I swapped them. Re-started the engine and the cooling fan then came on and ran continuously. Still had the check engine light and the same two error codes were present. So I then thought that the original sensor located in a metal elbow on one of the radiator coolant hoses needed to be plugged into the system, I took the original 'Y' harness that connected to the original housing and plugged it into metal elbow sensor, the other 'Y end (oval 4 pin connector) into the matching 4 pin oval connector on the new 'Y' adapter harness, and the 4 pin oval connector on the new 'Y' harness into the matching connector on the ECM harness. Started the engine and the check engine light went out, the engine was running smoother and I thought problem solved..... but no. After a couple of minutes the check engine light came back on and after the engine warmed up for a few minutes the yellow coolant temperature warning light came back.

Does anyone have any ideas? Did I get a bad replacement thermostat housing unit or do I have a problem elsewhere. I'm tempted to reinstall the original housing as I didn't get the yellow coolant temperature warning light with it.

 

I didn't think you could swap the ends of the Y harness... at any rate, read the live data to see what the ECU is reading. and YES it is possible the new unit could be faulty.

 

Problem resolved. Had air trapped in the system. After squeezing both radiator hoses for several minutes the cooling system returned to normal operation and the check engine light is gone. And for those who are going to ask why I didn't just use the bleeder screw on the thermostat housing, the replacement I got from Rock Auto didn't have a bleeder screw.