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Steve, BMW Expert
Category: BMW
Satisfied Customers: 25228
Experience:  BMW Expert
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Hi, I was driving last night and noticed the heating suddenly

Customer Question

Hi, I was driving last night and noticed the heating suddenly stop blowing warm air, and blew cold air instead. About 2 miles on, an overheating message came on. As I'd reached my destination I parked up and gave the car plenty of time to cool down aprx 5 hours.

The same problem arose on the journey home.
Any ideas what this could be?
I've checked the coolant and it seems to be at the right level, the oil is ok and I get no warning lights on the dash or in the Idrive.
I noticed that within a minute or two of starting the engine, the fan comes on and off every few seconds, or certainly sounds like it.
Any help would be greatly appreciated.
I have a 2006 523i
Submitted: 4 years ago.
Category: BMW
Expert:  Steve replied 4 years ago.
This would most likely be a failed water pump or thermostat. Typically you would replace both at the same time. It is also possible that the drive belt came off, the headgasket blew, or some kind of restriction developed in the cooling system. Pump or thermo most likely, though.

Sorry if you were hoping for a different answer, please don't shoot the messenger - I can only give the honest answer, which I have. Please remember that a low rating PUNISHES me for my honest and prompt response, and I receive nothing for my time and answer until a positive rating is clicked.

Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle.
Customer: replied 4 years ago.

I've had a quick look and the water pump seems fine, the thermostat looks shot though.

Do you think I should change them both, or just the thermostat?

Expert:  Steve replied 4 years ago.
I think you should change them both, as I said. Kindly please select a positive rating. Thank you.
Customer: replied 4 years ago.

I can't quite see the point, the water pump is €500 + vat

that's a very expensive add on.

Are you sure it is worth it?

Expert:  Steve replied 4 years ago.

This is the prudent choice and worth doing while you are in there and will likely prevent a future overheat (ie preventative repair). When the thermostat fails, the pump isn't usually far behind. Ultimately it is up to you, you can make your own decision. Please kindly select a positive rating so that I receive credit for my time and answers. Thank you