BMW E36 325 car wash problem

This problem can occur when you drive your E36 325 though the car wash and it fails to start or the engine starts to act up. It's because the engine computer just went under water. The engine and (auto) transmission’s ECU are located to the right of the heater/ac box in the firewall cowling. The heater/ac has to take in fresh air, and it does it at the base of the windshield. But it also has to shed water through a drain tube that’s looks like an elephant trunk. This tube fills up with debris and when you drive through a car wash all that water has to go somewhere—right into the ECU box in the cowling. The engine's ECU is at the bottom of this box and drowns. If this happens, the repair is to replace the control unit. This is expensive and each control unit has to be coded to the car, meaning a trip to the dealer.

Before this happens you should think about replacing the cowling drain tube with the updated one from BMW. There are a few different part numbers so call your nearest dealer for the part. On some of these cars it can be a bear to replace that tube.