[leot]

2007 X-3 3.0. Noticed it took a long time for the heat to come on, once it came on it was fine the rest of the day, even if I shut the car off for long periods. Next morning same issue. Seemed like a thermostat was stuck? Then all of a sudden it got worse, the temp gauge would shoot up into the red, still no heat, then you could tell the thermostat would open because the temp would drop almost instantly to normal and the heat fan would come on (auto climate control) Fluid was good, no other work was done on the car recently that someone could have messed it up.

Just seemed so obvious it was a thermostat. Bought a new thermostat for $115!! and was a PIA to change, followed the procedure for bleeding the air out. Got in the car yesterday morning and tried to let it warm up, no heat, but temperature at normal or slightly above. Drove 2 miles, temp shoots up to red, pull over for a few minutes, sudden drop in temp and the heat comes on..., runs fine the rest of the day and night. Sure seems like a thermostat sticking but I changed that!!


The fan on the radiator is coming on so thats ok, in fact it only really over heats when driving. It seems like it has to get very hot for the thermostat to open and let water into the heater. There is no heat in the car at all until the thermostat opens.

The car can sit for an hour at idle and not overheat, gauge half way, but no heat. If I rev the engine or drive it the gauge will shoot up.

Changed the coolant temperature sensor..no luck.

No check engine lights, put my code reader on and showing a P0597 which seems to be a thermostat heater control circuit open??

any ideas?