Our 1993 Merecedes 190 E (4 cylinder) is making a loud squealing noise when first cranked up. It started about 2 weeks ago and was minimal but now has grown to lasting about the first 5 minutes of the drive (my guess is that the car heats up enough and then the squealing stops).

I have been told it is the serpentine belt which is inexpensive to replace. I have also been told it might be the belt tensioner that may cost as much as $500. What do you think is the problem?

Squealing is usually a bearing center in one of the pulleys.
CAREFULLY with the engine running wearing thick gloves hold a bar of dry soap to the inside of the belt and if the noise goes away replace belt if not look further again I repeat CAREFULLY.
If you don't feel confortable trying this take it to a shop.

Hi there,
In my opinion, the suggestion offered by rdanz is very bad advice, and a real good way to lose a finger or two! The squealing is most likely caused by the belt slipping on the alternator pulley when it has a heavy charging load right after the car is started. Replace the belt, or have it replaced. If the tensioner has gone bad, replace it also. Don't fool around under the hood with the engine running! Too many rotating parts that don't care about your one-time-only limbs!!

Richard Wooldridge
'82 300D/4.3L V6
Etc...