The BMW 5 Series, particularly those equipped with the B58 engine, may exhibit slow coolant loss. One potential source of this issue is a leak in the remote radiator located at the bottom front right of the vehicle (passenger side on left-hand drive models). This radiator, positioned behind the fog light, connects to the main radiator via two long coolant hoses. A slow leak in this area can result in a minor drop in coolant level in the expansion tank, roughly between the minimum and maximum fill lines, over approximately 10,000 miles.
One way to diagnose this potential leak is to inspect the area for signs of dried coolant. A discolored splash guard beneath the remote radiator can indicate a slow seep, potentially from one of the lower fittings. This type of leak is more likely to occur when the cooling system is pressurized and at operating temperature. Accessing this area is relatively straightforward. By raising the front right corner of the car and removing the front right wheel liner, the remote radiator and splash guard become visible for inspection.
While a minor coolant loss over an extended period may not necessitate immediate dealer intervention, monitoring the rate of loss is crucial. If the rate increases significantly, professional diagnosis and repair are recommended. Regularly checking the coolant level in the expansion tank and inspecting the remote radiator area for leaks can help identify and address this potential issue in your BMW 5 Series. This proactive approach can prevent more significant cooling system problems and maintain optimal engine performance.
