Replacing the Auxiliary Water Pump
on the W126 1985 300SD
by whunter
12/28/04
The Aux water pump is there to flow hot coolant through the heater core at low engine RPM.
Without this pump, most drivers would never have heat.
Here's the procedure:
- Open hood.
- Disconnect and remove battery.
- Remove weather seal from false bulk head = blue line in attached picture #A.
- Remove four access panel screws = red dots in attached picture #A.
- Remove access panel = pink line in attached picture #A.
- Remove the silver processor box from bracket and lay it back on the bezel.
- Remove the three hoses where they pass through bulk head.
- Trace the aux pump wire to the plug and disconnect it.
- Remove the wire from mono valve.
- Remove two 10mm bolts holding mono valve, you may need pliers to hold the bottom nut unit.
- Remove the upper hose from the mono valve.
- Remove the water feed hose going through false bulk head to aux pump.
- Remove the two 8mm bolts supporting the aux pump isolation bracket.
- Remove the pump and mono valve assembly as a unit, use great care.
- Note orientation of aux pump to mono valve.
- Remove aux pump from mono valve.
- Remove aux pump isolation bracket from old unit and install on new unit.
- Install new aux pump to mono valve with correct orientation.
Reverse order # 14. - #1. and you are done.
Mine was nasty; it took two hours in the shop with all correct tools.
I hope yours is easy.
Have a great day.
- whunter
CategoryDiy
