Aux. water pump, What's it's purpose?
 

Could someone please tell me what the purpose of the auxillary water pump is? When should it come on? What if it doesn't? Any help would be appreciated. thanks, andy

It was my understanding that the aux. water pump is supposed to ensure that coolant gets to the heater core at lower RPMs, so that you have heat when the car is idling.

Mike

That is also my understanding. At idle, waterflow is not sufficiant. In my '75 300D, which does not have an aux pump, I used to rev the engine every once and a while to get heat out of vents while my wife and I parked at the ski slopes and watched the skiers at night.

Trust the two Mikes
 

The Florida fellow must be confused by the many front-drive cars which have a circuit to turn on the electric cooling fan when the ignition is off if underhood temperatures create a possibility of vapor lock.

Thank You, TK, I leaned something new,
 

at least about 124 cars -- I've got a 123 Diesel ('85 300TD) and I wonder if it's true of them too (mine has never been over 85 on the temp gauge)? I'll have to try to make my new CD manual work this weekend and find out, but I've been having trouble getting it up and running.

To: Fimum Fit - if your CD is browser based like mine. A little hint - mine worked erratically or not at all. To make long story short - read the readme text on the CD. I already had Acrobat 3.0 installed when I installed Acrobat 4.o off the cd. They conflicted. Removed both versions and re-installed Acrobat 4.0 from cd and all is well.:D :D

Andy,
The other issue is that if your aux water pump draws too much current (I don't remember the specs), it will eventually fry your pushbutton climate control panel. If you think yours is not working properly, it would be good to get those specs and test the current draw to avoid collateral damage.