Noise from water pump when cold

Over the past few weeks, I've been hearing a whiny, grating, whirring sound coming from the engine upon start-up. It would go away after a couple of minutes as the car began to warm up. Took to local MB tech and left overnight for cold start. He put stethascope(?) to various parts and said it's the waterpump. I didn't have the $600 at the time, so I've been stalling. Not much change until recently. As the weather is getting warmer, and my garage temp climbed from about 55 to 60, I don't hear the sound any more at all. Pump still seems to be working (driving temps OK and no coolant everywhere!). Any ideas?
--TIA, Mitch

Mitch,

$600 sounds rather steep for a water pump replacement but you didn't id your model. Perhaps for a 500SL, I dunno, but my 1989 300TE should have been alot less than that. I did the water pump, serp belt tensioner, tensioner shock, and air pump for about $600 but that was doing the work myself and getting good deals on the web. Still, shop around if you can and see if your MB tech is out of line.

Duh, sorry. '94 E420. Any thoughts on the noise/no noise thing???

[JDUB]

If your water pump is on the way out you can put your hands on the water pump pulley and notice some play. You will definately feel some play. If you dont it could be something else such as the tensioner pulley bearing or alternater. Check it out for yourself if you are confident.
Good luck my friend.

[Ron Miller]

What I would do, if i wantdd to diagnose it myself, would be to some time when the motor is cold and you have time, loosen the serpentine belt and take it off of the pulleys enough to spin all pulleys by hand. I would have swore my pump was going out, but it was the fan hub bearing. I found out what it was by removing the belt and checking each pulley. Good luck.

[can-do]

Greetings Mitch,

Look at a few things and see what you come up with. Seeing as most all water pumps have sealed bearings, the seals go before the bearings do. If the seals are actually going out on your pump, then it should be spitting coolant from the spit hole located on top of the water pump housing, and if that's covered up by the harmonic balancer at all, you'll have to feel around the hole after the engine is shut down for a wet spot. The other item, and one that most folks overlook is the belt that drives the pump. Although it appears fine and dandy, it may either be slipping or has glazed over the contact surface enough to cause this noise during start up then go away after the belt has flexed enough to become limber again. Both are cheap alternatives to troubleshoot or repair, and if in fact it is your pump that is leaking and grinding, do it yourself and save the bucks on labor, the part can't be that pricey.


Charles

Mitch,

The air pump on the M103 is a weak point. Specifically, the bearing in the electric clutch on the air pump is a weak point. No one will sell a replacement bearing and that is usually the failure point. Rebuilders revers engineer the bearing and get them in large quantities. I tried to get this bearing and even found the manufacturer in Germany but found the had an agreement with the EPA they wouldn't sell "user serviceable" parts to emissions equipment in the USA. You can fudge and get another bearing that is close and machine the clutch housing but you lose your ability to return your air pump for a core charge if they figure out you cut into it to make another size fit.

Good luck!