squealing serpentine tensioner 190D
 

My 1984 190D has started to make a high pitched squeal and it seems to be emanating from the serpentine belt tensioner apparatus. It looks like there are 4 parts ( 2 shocks, a pivoting tensioner and a pulley). I'm guessing the pulley is at fault here. The service manual for the 601 is in the mail and hopefully I can diagnose from that but I'm impatient and wondering if anyone can give some info from experience so I can go ahead and order the necessary parts.

Thanks

Kevin
1979 240D manual
1984 190D manual

Take a close look at the belt on the tensioner. You are looking at the grooved side there. If there are cracks in the ribs, likely the squeak is the belt slipping (mine started squeaking this winter and I put a new one on in conjuction with a new head gasket. No squeak).

Also verify tha the tensioner pulley isn't canted outward at all -- it if is, time for a new part (I think you get the pulley and arm, but you need to replace the whole assembly if it's bad). This will eventualy start banging around and can punch a hole in the front cover, so fix right away.

Usual cause of a "chirp chirp chirp" squeal is a bad belt. A continuous scream or squeal is more likely the bearings in the tensioner.

It's easy, for once, to check -- stick an exenstion into the block at the top of the spring, remove the nut on the through bolt, push down on the extension to unload the tension on the bolt, push it back, and allow the spring to relax by letting the pressure off the extension. Belt can now be removed or at least pushed off the tensioner pulley and you can spin it to see if it's smooth.

Peter