I have a 2006 BMW 325i, it was overheating so I checked symptoms and figured it could be the water pump. I told the mechanic to replace it but they called BMW and were instructed to replace the thermostat instead and they did. It overheated again and the fan is running fast during idle. When I drive the heater will go cold and that's my heads-up that the yellow temp warning is about to kick on followed by red. Any suggestions?

I think you are spot on. Same has happened to me, 70k. almost on the dot! I will do a diagnostic, get the codes and go from there. The thermostat, water pump, vanos, switch over foo foo valve, they are all electronic, so a diagnostic scan is essential. I think you are spot on. Same has happened to me, 70k. almost on the dot! I will do a diagnostic, get the codes and go from there. The thermostat, water pump, vanos, switch over foo foo valve, they are all electronic, so a diagnostic scan is essential.

The coolant pump is most definitely not electric. The main fan is bolted to pump shaft. It is driven by the main serpentine belt. Only the auxiliary fan is electric. (There is also an auxiliary small water pump which is electric, but it is not for main engine cooling.) Whenever your car is overheating, the first thing you do is check and replace the water pump. Guarantee its failed. Next replace the thermostat, which you have already done. Finally, Given the age of your car, replace the main fan clutch. Thee fan may look like its spinning, but if the clutch has failed, it wont spin fast enough to cool the engine.

PS: if you took it to a place that had to call BMW to ask what to do, for something simple like this, then you went to the wrong place. Do NOT take it to the local quick service place and think they will do ANYTHING on this car correctly. Save your money and go at least to an independent BMW mechanic. I guarantee he wont have to call the dealership to change the water pump. The coolant pump is most definitely not electric. The main fan is bolted to pump shaft. It is driven by the main serpentine belt. Only the auxiliary fan is electric. (There is also an auxiliary small water pump which is electric, but it is not for main engine cooling.) Whenever your car is overheating, the first thing you do is check and replace the water pump. Guarantee its failed. Next replace the thermostat, which you have already done. Finally, Given the age of your car, replace the main fan clutch. Thee fan may look like its spinning, but if the clutch has failed, it wont spin fast enough to cool the engine. PS: if you took it to a place that had to call BMW to ask what to do, for something simple like this, then you went to the wrong place. Do NOT take it to the local quick service place and think they will do ANYTHING on this car correctly. Save your money and go at least to an independent BMW mechanic. I guarantee he wont have to call the dealership to change the water pump.

Like I said It is possible with todays engines. to have a "Air Lock" situation. Many times it will give an overheat condition which will break the airlock. then when filled again all is good. If your heat is working properly and (if you have a coolant temperature gauge) the coolant temp stays in the normal operating range. I would suspect you had an airlock that cleared with the overheat. Keep checking your coolant level and if you see no problems in about a weeks time ( depending on how and how much it is driven) I would say you should be good to go. Like I said It is possible with todays engines. to have a "Air Lock" situation. Many times it will give an overheat condition which will break the airlock. then when filled again all is good. If your heat is working properly and (if you have a coolant temperature gauge) the coolant temp stays in the normal operating range. I would suspect you had an airlock that cleared with the overheat. Keep checking your coolant level and if you see no problems in about a weeks time ( depending on how and how much it is driven) I would say you should be good to go.

If you are still having overheating issues. I would have the car scanned to see if the sensor may not be accurate. also have the radiator checked. If you are having poor heat this may be a sign of the cooling system getting plugged. If that is happening you will have poor heat displacement in the radiator. Making sure all components are working properly. Cooling fans coming on at the proper time etc... If you are still having overheating issues. I would have the car scanned to see if the sensor may not be accurate. also have the radiator checked. If you are having poor heat this may be a sign of the cooling system getting plugged. If that is happening you will have poor heat displacement in the radiator. Making sure all components are working properly. Cooling fans coming on at the proper time etc...