Replace BMW Heat Exchanger

This bulletin applies to BMW 2 Series, 3 Series and 4 Series vehicles equipped with an automatic transmission. The Service Engine Soon light may be on, with fault code 1D2008 (map thermostat jammed open) stored in the DME.
Oct. 2, 2023
2 min read
Mitchell 1
Example of the softer rubber outflow hose location.
Example of the softer rubber outflow hose location.
This bulletin applies to BMW 2 Series, 3 Series and 4 Series vehicles equipped with an automatic transmission. The Service Engine Soon light may be on, with fault code 1D2008 (map thermostat jammed open) stored in the DME. There may be a complaint of low heat output with lower outside temperatures. 

During engine warm-up, the engine coolant does not reach operating temperature within the DME’s allowable time limits. This is caused by either a faulty thermostat inside the transmission oil heat exchanger or a faulty engine map thermostat.

Remove the front underbody protection panel to access the cooling lines to the transmission oil heat exchanger. Clamp off the outflow hose on the cooler with special tool 81 64 2 184 117. The outflow hose is the softer rubber of the two cooling lines on the heat exchanger. After clamping, remove the outflow hose from the heat exchanger.

Loosen the cap on the coolant expansion tank. If any coolant starts leaking out of the transmission heat exchanger, the internal thermostat is jammed and the heat exchanger will need to be replaced.

Obtain and confirm the part numbers for the specific vehicle by entering the chassis number in either ETK or AIR which takes into account specific equipment and/or options. 

About the Author

Information courtesy of Mitchell 1

Information for Technical Service Bulletins comes from ProDemand, Mitchell 1's auto repair information software for domestic and import vehicles. Headquartered in San Diego, Mitchell 1 has provided quality repair information solutions to the automotive industry since 1918.

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