Secondary water pump operation

[Russell]

I have noticed my secondary water pump is on whenever the key is in position one at all times even when the heater fan is off and both heater temperature controls are in the off position. BTW, the driver's side temperature control is all way to the off (blue) position which should turn both sides of the car temperature control off.

Is this correct? TIA

[Mobius]

Mine does this too.

I don't know if it should or not, but if it shouldn't - we have the same problem.

[winfred]

that seems common on the later cars but i don't know if it's wrong, my 92 system doesn't do it, it may be something that they did so heat can be on without the engine for a short while, the e38/39 cars have a button to do this to get heat from the still hot motor

[shogun]

recently I changed my aux water pump as it was out of order since early this year. What I noticed:
-whenever I came to a stop at a red signal light or in traffic jam, temperature inside the car became less/lower. Probably because the water pump alone does not have so much conveying power in idle run of the engine.

After changing to a new aux pump this was eliminated.

Not sure, but the aux pump might even be of importance when both heater valves are closed. Maybe there is a return from the aux pump to the engine cooling. Have to look on the ETK to be sure.

[mikell]

I hate to dredge up this old thread, but is there a clear answer? Is it normal for the aux water pump to be "on" all the time? Mine is always on and it's beginning to make a bit more noise than before, so I have only recently noticed it.
Thanks.

[Jr ///M5]

E39's have a feature that consists of a "Rest" button on the HVAC controls. After you have stopped the car in the wintertime, and you still need heat without running the car, simply press the button. If it is below 50 degrees ambient temperature outside, the cabin blower will run and use the residual heat from the engine utilizing the secondary water pump to circulate the water through the heated block until the water temperature drops below a certain temperature.

Maybe the idea for the E39's originally came from our E34's set up, some engineer thought all I have to do is add this button....

[632 Regal]

another secret tidbit...didnt see that one in the manual.

E39's have a feature that consists of a "Rest" button on the HVAC controls. After you have stopped the car in the wintertime, and you still need heat without running the car, simply press the button. If it is below 50 degrees ambient temperature outside, the cabin blower will run and use the residual heat from the engine utilizing the secondary water pump to circulate the water through the heated block until the water temperature drops below a certain temperature.

Maybe the idea for the E39's originally came from our E34's set up, some engineer thought all I have to do is add this button....

[Bill R.]

sense out of it than i can...

I hate to dredge up this old thread, but is there a clear answer? Is it normal for the aux water pump to be "on" all the time? Mine is always on and it's beginning to make a bit more noise than before, so I have only recently noticed it.
Thanks.

[RobPatt]

....up by the battery post terminal near the firewall on the M50TU? Never knew where the aux water pump is.... thanks, Rob.

[Bill R.]

it

....up by the battery post terminal near the firewall on the M50TU? Never knew where the aux water pump is.... thanks, Rob.