Re: 86 735i no temp after replacing water pump (archive)

If you had a correct temp gauge before you started the water pump R&R, I would suspect trapped air in the coolant system is the cause. The sensor will not read hot air ,only liquid on it. Those wires down on the lower passenger side are the two thermo fan switches, one comes on at a lower temp and the front aux fan is supposed to kick in on the lower speed [via a resistor], then, if things are still getting hot, the higher rated switch allows the high speed relay to operate the fan at full battery voltage.

Good that you plugged them back in, they're the only extra measure of over-heat protection the vehicle has, and are also need for correct A/C operation.

Make sure the plastic tube going from the top of the radiator isn't plugged up with silicone sealant. This tube ends up at the expansion tank next to the firewall, coolant MUST freely flow through it to get the air to the tank and out of the system. Remove the expansion tank cap and try to see if coolant is flowing into the tank with the engine running from that port fitting.
I've seen silicone get stuck in the tiny upper radiator fitting from people using it to seal a new water pump or some other coolant part. Risky stuff to use on these vintage BMWs, too many small coolant passages to get lodged into.

If it is a bad thermostat, just remove and test it as others have posted.

Follow Ups:

Callan, Good to see you on the board again! (eom) Jon_745_MS 15:31 10/28/2001 (1)
- Re: Thanks, just dropped in for a quick view[nm] Callan 18:09 10/28/2001 (0)

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