BMW X5 F15 - coolant level warning message in the instrument cluster

In the case of the vehicle type mentioned above, a warning message may appear in the instrument cluster indicating that the coolant level is too low, or stating that the coolant level in the expansion tank has reached the minimum. In addition, a distinct smell of coolant is often noticeable in the engine compartment. There are not necessarily any drip marks underneath the vehicle, but on closer inspection, damp patches or crystallised coolant residues can be seen in the area between the alternator and the oil filter housing.

If the fault mentioned above applies, particular attention must be paid to the coolant flange (coolant neck) on the cylinder head (see illustration – installation location of the coolant flange). The component is made of plastic and, because of its installation position, is subjected to high thermal loads. Material fatigue may lead to hairline cracks in the area of the connection neck or spigot or also to leaks at the seal. As a result, coolant leaks out, particularly when the engine is at operating temperature and system pressure is rising. Because the installation location is concealed, the leak often goes unnoticed at first.

In order to troubleshoot the problem, the area around the coolant flange on the cylinder head has to be visually inspected thoroughly. Where necessary, a mirror or endoscope might need to be used. In addition, the cooling circuit should be pressurised using suitable test equipment in order to pinpoint the exact location of the coolant leak. If a leak is detected, the coolant flange, including the seal, must be replaced in accordance with the manufacturer’s instructions. As part of the repair, adjacent coolant pipes and hose connections must be checked for any further leaks, brittleness or damage.

Once the work has been completed, the cooling circuit must be filled, bled and pressure-tested again in accordance with the manufacturer’s specifications.

Once the cause of the fault has been eliminated, a test drive is to be carried out as a final step.