Below is a picture of a water pump from a M103 2.6 engine.

I assume the hole pictured is a breather hole. I also assume that the water trace from this hole indicates that the internal seal inside the pump is cactus and the water pump needs to be replaced as it can't be prepared.

The water pump is OK in operation - i.e. pumps coolant around very efficiently. I initially assumed I had a leak from the O ring between the block and the pump and replaced it. Further leaks have led me to this finding pf leaking from the breather hole.

New pump required?

That is a "weap" hole. When coolant drips out, the pump is DONE!

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Bummer!!

Actually it's a "weep hole", and if leaking coolant indicates that the shaft seal is shot. If you're using MB coolant typically the dry residue is white, not a rust color.

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Fred Hoelzle

The rust colour is because I have been using distilled water trying to get to the bottom of the water leak - didn't want to waste expensive coolant. Once I replace the water pump I will do a Citrus flush and install proper MB stuff.

Eeesh... Coolant also prevents internal rust, which it appears you are getting. Do a real good flush, but in the future never run pure water for that reason alone.


-tp

I've got a leaking water pump on an m103 and I suspect the coolant is leaking past the shaft seal. Just doing the research before replacing it and I'm wondering if anyone has actually taken the time to replace the 'casette-type' seal inside it which is apparently possible? I'm referring to MB job number 20-2250: Sealing Coolant Pump.

This looks like a slightly longer way of doing the job, but I'm questioning why I should throw away an otherwise perfectly good water pump?

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1988 300CE 124.050 M103.983
1986 190E 201.024 M102.962

Yes I found the same leak on my 300TE when I was rebuilding my head. I bought a new "Graf" pump and I was very happy with the quality...Its been running for 9k miles now without issues.
I would be weary taking a pump that has, I am assuming, over 100k+ miles on it all apart to replace a seal. I would replace the thing as it does and will fail you on. If you don't mind spending the hours on it, go for it and let us know how it went.

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Years ago, buying a rebuilt water pump was a very common practice. I've used many rebuilt pumps and for the most part they've lasted as long as new ones.
When they rebuild them, I believe they pretty much just clean it, reface the mating surfaces and replace the seal and bearing. You'd need some kind of press for the bearing. If you can get the seal and a cover gasket (and/bearing?) I don't see why you couldn't do it yourself.

These water pumps can be gotten for as low as about $100, so you'd have to weigh that against the time and trouble you'd go through to rebuild it.
It might be an interesting project though.

Best to buy a rebuilt water pump from your local MB dealer.

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Fred Hoelzle

My Graf (which i installed in august) is making a loud bearing sound already ..I have found another person reporting the same problem.....keep an eye on yours, hopefully it will be better than the one i have ....I would not recomond this brand based on what i've experienced .....by the way, mine was made in italy...

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1993 300E, 2.8 M104 .....

I just did the pump on my 89 300SE last week and got a new one at NAPA for $130. Quality of the pump looked very good. ***** of a job though.

Dan

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Thanks. I'll keep an ear open for it.

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