BMW E39 no warm air and temperature rising
Why does the E39 not blow warm air and the temperature rise?
The most common cause is too little coolant or air in the system, so no coolant reaches the heater core. The cause is most often a leak, not a cylinder head fault. Fill the expansion tank, bleed the system carefully and watch the coolant level and the heat output.
Where does coolant leak from in the M52 engine even though no leak is visible?
The thermostat housing cracks with age into a hairline crack, and the coolant evaporates quickly on hot surfaces. Other leak points are the hose clamps, the gasket at the bottom of the expansion tank, the radiator end tanks, the expansion tank cap and the water pump shaft. Dry the area and watch what gets wet first.
What else can be wrong if the coolant and bleeding are fine?
Stuck water valves or a dead circulation pump, which is in the same assembly under the valves. The water pump impeller can also be split, in which case bleeding will not succeed until the pump is replaced. A faulty expansion tank cap can cause the same symptom.
How is the M52 cooling system bled?
The factory bleeding procedure is enough once the leaks are fixed and the circulation pump works. The system has a heat accumulator, which makes bleeding more awkward. A bottle or similar aid is also needed to remove the last bubbles. The air only came out properly when the temperature was about 95 and the lower coolant hose was hot.