[BMW528iN53]

Hi all,

First time on here and I need help.

I went out on Friday night, when I started my car to return home, error came up "Battery discharge when stationary". I drove home fine, switched the car off and on to clear the code and everything was fine.

The next morning the car was completely dead. Called the AA, which advised there was a drain on the battery and recovered me to a specialist BMW garage. They have replaced the battery and the car struggled to start after 6 hours.

They parked the car inside the garage and noticed a noticed a noise even though the car was off and locked, which was the water pump constantly running.

The garage have been told by Auto Logic that they need to check the wiring between the ECU and the water pump.

Has anyone else had this problem or can advise please?

[AZ-MCRacer]

The water pump should run about 30 seconds after you turn off your car, but that is it.

[BMW528iN53]

It seems to be running all the time and cant find what is causing it. They have disconnected it and the car is holding charge.

[ezaircon4jc]

Originally Posted by BMW528iN53

It seems to be running all the time and cant find what is causing it. They have disconnected it and the car is holding charge.

Stuck relay (is there one?)?

[j0nblayz]

Sounds like a bad water pump, however bmw should be able to confirm that for you. I had a similar issue, where my pump would constantly run on high, but did shut off when I turned my car off. We replaced the pump, but had the same issue. Now they are saying I need to replace my Ecu, so just waiting on the part from Germany. Hopefully that’s not the case with your issue, I would start with get it checked with bmw and see if it is indeed the pump

[Surly73]

I do not have documentation handy to confirm, but...

The water pump is variable speed and controlled by the ECU. I would not be surprised if the wpump is always/often powered with a 12VDC supply and obeys ECU digital commands for how fast to run. (This is the same way vehicle with electric main cooling fans operate) Hopefully this means the water pump is bad - change it and you're done.

If it works differently (e.g. powered at variable voltage by the ECU) then you could have an ECU problem. I would expect that with the ignition off the ECU is completely unpowered, so I would not expect this to be the case.

Whatever way it goes - you do not have a "typical" or frequently seen water pump problem. Get professionals to diagnose and repair. It's not operator error. It won't just go away. The symptoms are not 100% conclusive such that we could recommend throwing parts at the problem.

Water pump replacement is your best case, though.

[BMW528iN53]

Originally Posted by Surly73

I do not have documentation handy to confirm, but...

The water pump is variable speed and controlled by the ECU. I would not be surprised if the wpump is always/often powered with a 12VDC supply and obeys ECU digital commands for how fast to run. (This is the same way vehicle with electric main cooling fans operate) Hopefully this means the water pump is bad - change it and you're done.

If it works differently (e.g. powered at variable voltage by the ECU) then you could have an ECU problem. I would expect that with the ignition off the ECU is completely unpowered, so I would not expect this to be the case.

Whatever way it goes - you do not have a "typical" or frequently seen water pump problem. Get professionals to diagnose and repair. It's not operator error. It won't just go away. The symptoms are not 100% conclusive such that we could recommend throwing parts at the problem.

Water pump replacement is your best case, though.

Thanks you all so much especially Surly73! I will let the garage know this information. It may be worth putting a metre on it to see the draw and if it is variable. If it is not then I will replace the water pump. Unfortunately its at a Specialist and not a BMW retailer.