alabrew

New 06 525i owner 85K miles. Having a little trouble during warmup. As I leave home, I may drive several miles w/o any heat. Most apparent when the temp. is lower than 40 degrees F. I have found if I stop, shut down, and turn on residual heat, I then will get heat when I restart. If I don't stop, I get an overheat warning.

What I think is going on is that the thermostat is not opening and that I am making it open with the residual heat. So is the thermostat the problem or is it the coolant sensor not telling the thermostat to open. Once I do the residual heat trick, I can drive the rest of the day w/o issue.

A little history: I did a drain, flush, and fill of the coolant (the dealer only had 20 degree freeze protection and it got down to 15, causing the car to overheat) and during the purging step, I noticed that the pump pulsed rather than continuously pumped - could it be bad too? I runs fine on the highway so I figure it has to be OK.

I know to change both pump and thermostat if you are changing either one.

seanjordan20

I would do the temperature gauge first because it is cheap to do yourself but I doubt it is your issue. Did you use 50/50 or straight 100. it has to be 50/50 or that will cause it to not reach temperature. When I had this issue the dealer changed my thermostat and housing and that fixed my issue. If you are saying that your car worked fine before the change then make sure you used the right fluid. I would have went to the parts store and just bought some 50/50 fluid. I found out that BMW uses regular yellow fluid once your car is not under warranty so no need to buy it from the dealer.

twh

alabrew, you should pull the codes. It could be your water pump is still working, but on it's last legs. I had some come codes talking about RPM of the water pump isn't what is expected for a year before it finally failed. Water pump in my 2006 530xi worked until one day I got a yellow iDrive "drive gently" message. That's also an indication the pump isn't totally gone, but not working right. Wife's X5 one day just went out suddenly and got the red "pull over" message.

My local BMW dealer sells a gallon of BMW Coolant for $19.98 if I order online and pick it up. Get some distilled water from the auto parts store or grocery store. Don't use tap water. As I recall, water pump and thermostat replacement needed about 2 gallons of liquid exactly.

alabrew

Thanks for the suggestions. Yes, I pre-mixed full strength coolant with distilled to 50/50.

Drove it yesterday with temps. in the 50's and it warmed up and gave heat as expected. Only in the 40's and below does it not act normally.

Making me think it is a sensor rather than the thermostat since the thermostat receives a signal from a sensor to start to open?

Hate to change the pump and thermostat if it is really the sensor. Currently don't have a way to pull codes myself, will Auto Zone's reader work?

twh

I don't believe you can't get all the info the car has to offer with Auto Zone code reader. Get a cable and BMW What app or download the INPA stuff from the Internet.

If you know your car has the original water pump, it will go at some point in the near future. So, even if that doesn't turn out to be the issue, don't feel bad about doing the work, because it's going happen at some point. My 2006 and 2009 BMW's both have new water pumps at about 60K miles.