I just had my Harmonic balancer replaced on my 112 (car is a '98 C280). When I picked the car up I drove a short distance to the gas station. I got out of the car and it was running I could hear what sounded like the belt squeeling. I immediately took the car back to the dealership and of course the service dept. had just closed for the day. I brought the problem to the General Managers attention, he said no prob. we'll take care of it tommorow. So I called the following day to schedule an appointment. (The balancer was replaced on Monday-meanwhile the squeeling is getting more apparent) They said the soonest they could get me in was Fri. morning. I took the car in today,my service advisor told me that the tech. probably forgot to adjust the belt tension. A few houres after I dropped it off my servive advisor called me and said (guess what) "the squeeling is coming from your water pump, we can replace it for you today for $640.00". This problem did not exist before the harmonic balancer was replaced, and the car has never run hot. What do you all think, could improper belt tension take out my water pump? Or is this just one of those "things"?

Sounds to me like someone is lying to you. Personally, I would insist on being shown just how the water pump miraculously failed independently at almost the same time. However, there is an exception that I see here. Was the harmonic balancer replaced BEFORE it failed or AFTER? If it flew off and struck the water pump, it might have gotten damaged, but it's still hard to believe they wouldn't have seen clear evidence of that. If the HB was being replaced as a warranty/recall, someone wants you to pay for the mistake they made breaking your water pump. Someone owes you some d*** good proof to the contrary. Good luck!

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

It would be difficult to over tension the belt because the belt tensioner on most late model Mercedes engines are spring loaded. The tension, or preload, is engineered into the device. I would be more inclined to think that it was dumb luck mixed with a technician who was interested in his flat rate time! It is possible that the technician allowed the hub holding tool to rest against the water pump housing while removing/reinstalling the crank bolt. Bad practice, seen it a few times. A well seasoned, tuned into his work technician is a rare commodity in most if not all dealerships nationwide.

I am sorry to hear about an experience that appears to have been avoidable.

I just wanted to add.......I'm not trying to rip anyones head off. I have warranty (an extended aftermarket one) on the car and they are covering everything except $93.00 outta' pocket. The dealership has my car now and they gave me an '05(or '06?) C240 for the weekend. It could be way worse, I guess. I am just curious how this might have happened. Thanks for the replies so far y'all.

and the balancer was replaced before it failed.

As is often the case, a little more information may shed some light.

How many miles on the water pump? The water pump should last, on average, about 80k to 120k mi. Could be more, shouldn't be less.

What's the history of the cooling system? Unless it's been without incident there are several things to consider:

Have you ever changed the coolant? What brand and type did you use?

Have you ever had to add coolant because of a leak? How low did it get and for how long was it leaking. Has anyone ever added straight water to the system in an emergency?

Cooling systems are usually pretty bullet-proof for the first 4 or 5 years, and after that things can start to deteriorate. Check this web article for a general overview on water pump replacement.

Make sure you ask for the old parts to be returned to you. Check for any radial play in the pump shaft. There should be very little, if any discernable play. Some will say that any play is grounds for replacing the pump, but on my own 300E I replaced the pump at 120k mi. just because I was in there for other repairs and it seemed like a smart thing to do. Upon removing the pump there was noticeable play in the shaft, but no sign of any leakage past the seals. There may be some axial play, but that's not as critical. Check for evidence of leakage or staining at the water pump weep hole (see pic below). This is your first indication of a failing pump shaft seal. Here's an earlier thread that notes some of the symptoms of a coolant leak on an M103 engine. Have you noticed anything similar on your car in the recent past?

And of course, there is the chance that the technician somehow screwed it up, but it would be pretty hard to do unless he bent the shaft or cracked the housing, both of which would be pretty obvious. I can't really think of a scenario where he could cause some hidden damage that would cause the pump to freeze up and fail. They're pretty stout pieces.

Discuss your concerns with the service manager and ask him to give you a detailed explanation of what they feel the failure mode is, and have them show you on the pump itself. If they do this to your satisfaction, take their word on it. If not, let us know what he says and show us pictures of the old pump.

Hope this helps,

Gary

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It's the original pump with about 90k on it. The car has allways been maintained by the book. The car has never leaked, and never has straight water been added to the cooling system. The need has never arised. I guess it's just "one of those things" with coincidental timing. I'll check out the original part when I pick my car up either Monday or Tuesday. Again, thanks for the replies.