Last week we had a customer with a 2011 BMW X5 come in with an overheating problem. Since the 2011 BMW 530i does not come with a temperature gauge it can be very disconcerting when the instrument display is telling you your car is overheating. The customer stated that he saw the warning and also heard the engine auxiliary fan roaring at full speed. Now when the customer told me this I already had a good idea of what may have happened.
BMWs with N54 or N55 motors (between 2008 and 2014) come equipped with a electric water water pump. The electric water pumps were installed to make the engine more efficient in terms of power, fuel consumption and emissions. It does this by letting the computer control the flow of coolant rather then the engine itself. By removing the old mechanical water pump there is less load on the engine. The old mechanical style water pump could rob as much as 3 to 5 horse power from the engine.
The first thing we did was to check the coolant level and then connect the car to the Integrated Service Technical Application (ISTA / BMW factory tool). The coolant level was ok. Then we checked for codes. There were two codes related to the water pump. Digital Motor Electronics (DME) 20A804 - coolant pump switch off due to blockage and DME 20A701- coolant pump speed outside of tolerance. The second code coolant pump speed outside of tolerance definitely means that the water pump should be replaced.
The customer also stated that the engine auxiliary fan sounded very loud. This higher auxiliary fan (engine radiator fan) speed is normal. The DME sees that the engine temperature is raising even though the computer is commanding the water pump to move more coolant. The DME is trying to remove heat from the engine with air as a precaution.
One of the reasons I wrote this article is because the electric water pump can just pop up at any time without any warning. Once it fails the car is technically not drivable. One other thing that can accelerate the water pump failure is if the engine oil filter housing gasket leaks. On the N54 and N55 motors the oil filter housing sit almost right above the electric water pump. It’s like dripping oil on to your vacuum cleaner. Eventually something is going to fail.
We always replace the thermostat with the water pump as it has been updated on some of the engines and it is next to the water pump. If oil has been leaking from the oil filter housing gasket. We also replace the gasket and any rubber hose that may have been covered in oil. If you have one of these cars and the water pump has not been replaced yet and you have more than 80,000 miles you should have them checked. Even though both repairs are expensive it’s better to have them checked or replaced before they cause bigger problems. Thanks for reading.