Fixed Auxiliary Water Pump!! - PeachParts Mercedes-Benz Forum

tobybul · #1 11-18-2006, 11:31 PM

Just want to share what I did today and clarify how I did mmine...

1984 300D
Problem: not getting enough heat. found aux pump was seized when I applied 12vdc to terminals.

What I did: removed aux pump assembly from car (disconnected hoses (plugged ends with cork), some coolant spilled to pan on floor).

Materials/Cleaners Used:
The Works toilet cleaner (mild acid solution)
Purple Cleaner (degreaser)
Black silicone tube (sealant)
Machine oil
Contact Cleaner
Fine grit sandpaper (I used 400)
Goggles for eye protection
Nitrile or latex gloves

Put on gloves. Dismantled motor (see pics). Removed back plate and slid housing out. Noticed crud and corrosion inside of housing surface. It appears moisture seeped in over the years.

Put on goggles. Work in well ventilated area. Coated/squirted housing with mild acid solution to remove lime and crud. Used degreaser (purple cleaner) on armature part. DO NOT USE the mild acid on any part of the armature. Do not mess with brushes nor pull out armature from pump assembly. Let soak for a few minutes. Scrape crud off if necessary.

Rinse housing and armature with water. Make sure acid or solution are totally rinsed off. Repeat process if still dirty.

Dried all items using shop vac first then hair drier. Sanded armature plates lightly. Sprayed contact cleaner on armature assembly.

Reassembled all parts. I lightly oiled the back plate where the shaft goes into. I sealed the joints using silicone to prevent moisture from seeping in the housing. (no real need to mark orientation of housing b4 dismantling as its easy to figure out how to put it back on). Tighten screws and test. Works now. Reinstalled back to car. Test drove and heat is great.

Will be rigging up in-line fuse to protect CCU in case motor conks out... I don't know how necessary this is as my aux pump is the orig and my CCU is stil fine.

#2 11-18-2006, 11:52 PM

Darn, I thought you fixed the water pump end. Mine was dripping and I never got it to seal. I just replaced it with a brass elbow fitting. No problems with heat, it's like a blast furnace when it gets past 60*c.

whunter · #3 11-19-2006, 05:13 AM

Added to

Climate Control:
Climate Control:

jt20 · #4 09-12-2009, 12:08 PM

thats impressive.

I've tried to revive 2 of these seized pumps now. They were beyond repair, I couldn't even get the housing off without causing more damage.

lietuviai · #5 09-12-2009, 06:14 PM

I had a seized one on the 1st 300D I owned 5 years ago. I recall trying to take the motor apart but it seemed like it wouldn't come apart like this one.

a2t · #6 09-13-2009, 10:11 AM

Quote:

Originally Posted by jt20

thats impressive.

I've tried to revive 2 of these seized pumps now. They were beyond repair, I couldn't even get the housing off without causing more damage.

me 2. Im glad you got it fixed but i'd also be worried about the plastic ports for the coolant hoses to attach to. they become brittle and break. and that would be potential for a huge coolant leak. there must be an aux pump from a ford or chevy that fits in there for $25 at autozone...

sasquatchgeoff · #7 11-03-2009, 05:55 PM

When I took mine apart at the volute end, the seam was sealed by a funny looking teardrop shape o-ring. Mine was leaking from this seam. I guess finding that gasket short of getting on a plane to Sindelfingen will be like finding bigfoot fossils.

Guess I better help the worn o-ring along with some black RTV...

sasquatchgeoff · #8 11-01-2010, 11:56 AM

The "funny looking teardrop o-ring just turned out to be a regular o-ring that kept its shape when sitting in the pump for 260K miles. It is a simple fix. No RTV required.