I have a shrieking sound coming out of the area around the drivebelt. It has progressively gotten louder. It starts making the noise a few minutes after the engine is started. I thought at first the belt was loose. I tightened the belt a little bit but did not help any. After listening closely, it sounds like it's coming from the water pump. Has anybody have any experience similar to this? Is it the water pump? What does it take to replace a water pump?

Another thing, when I tightened the belt, I'm not sure if I overtightened. The marker is broke. How can I check? Any advice.

If the water pump is failing as you describe it will be leaking profusely shortly. The shaft seal can make noise like this if it is operating un-lubricated, and it will very shortly wear out. The seal is normally lubricated by the coolant, so, if you have changed the coolant and either used an anti-freeze that is not compatible with the engine materials, or not used any anti-freeze at all, you may be stressing out the seal. However, I think it is more likely one of the pulleys, idlers or other driven components, might have a bad bearing. I would suspect the idlers first. Try loosening the belt entirely and turning the idler and other driven equipment pulleys by hand. Good luck, and I hope this helps. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Thanks a lot. That's quite helpful. I will do that. I'll check out the idler and other pulleys after loosening the belt. Is the idler the same as the tensioning roller?

I just changed the waterpump on 87 MB 190E 8V 2 weeks ago. Before i changed the waterpump, i also think that the noise came from the belt or tenioner.....

After cold started few mins later, it starts very noisy. When you press the gas, the noise becomes louder. Ended up i changed the waterpump and whole car quite!! Hope that this case can help u out.

That sounds exactly like what I'm experiencing. I'm quite certain that the noise is coming from the water pump but I don't see any leaks. I'll loosen the belt and check the other pulleys including the tensioner, just to be sure. Then I'll tackle the water pump.

How long did it take you to replace the water pump. I know you have to remove the fan, radiator and thermostat housing. Seems like a lot of work. Any tips, shortcut, things to look out for.

on my car, it took about 3 to 4 hours to replace. I took off the fan blade, alternator, thermostat housing and fan shoulder. Don't need to take off the radiator.