BMW E60 automatic gearbox heat exchanger and its thermostat
What does the BMW E60 gearbox heat exchanger do?
The heat exchanger is connected to both the coolant circuit and the gearbox oil circuit. It has two identical thermostat elements, which open when the gearbox oil warms up to about 90 degrees. Coolant then starts to cool the gearbox. The part number on the 525xda is 17217803830, and the part comes with the thermostat.
How is the gearbox heat exchanger replaced?
1. Remove the front underbody shield. 2. Disconnect the coolant hoses from the quick connectors. 3. Disconnect the oil inlet and outlet hoses at the 10 mm bolt. 4. Remove the heat exchanger from the block with three M6 bolts. Only a decilitre or two of oil runs out. Raising the front of the car reduces the spillage.
Can the heat exchanger be the reason the engine does not warm up?
Yes. If the temperature stays low and replacing the main thermostat does not help, the fault can be in the heat exchanger's thermostat. The thermostat may not be available separately, in which case the whole heat exchanger is replaced. New gearbox oil is yellow, not red.