1992 400E aux water pump location?

[E93067]

Trying to locate the aux water pump to the heater core on a 1992 400E. My heater stoped working and I suspect this part may be at fault or was left dissconnected after my recent valave job.

Have attached a very part pic, it hopes that someone could help me locate its location. Hopefully its accessible and does not require the removal of any major parts like intake manifold or the radiator.

Thanks