M103 belt still squealing after replacement
 

My 190E Sportline has always had belt squealing problems that I've tried to address to no avail. I've replaced the tensioner twice, one was Febi, one was INA, both German made, INA is OEM. I've replaced the belt four times because of wear occurring, Dayco, Gates, and MasterPro. I've replaced the idler pulley twice. I've replaced the smog pump with a rebuilt one, I've replaced the alternator with a rebuilt one, I've replaced the AC compressor with a new one, I've replaced the power steering pump with one that doesn't leak. I've replaced the pulley on the power steering pump and water pump with what looked to be fairly new ones. The fan pulley bracket bearing has no slop in it. The water pump I haven't replaced but it doesn't seem to have any issues, no slop in it at all. Does anyone have any ideas why I would still be getting belt squeal when basically everything should be in working order? My other 190E Sportline has none of these issues.

Presumably you routed the drive belt correctly and adjusted the tensioner correctly. The old style tensioner with the pointer and scale can be troublesome to tension correctly. The squeal could be due to a slipping drive belt.

Could you describe the ruckus?

Is it a rhythmic chirp or a continuous squeal more prevalent just after starting the car ( High alternator load )

When you mist water on both sides of the belt, does the noise go away?

What sort of wear are you getting?

The bearing can be very dry and still tight. If you spin the fan bearing, does it coast without resistance? If so, there is very little to no grease in the bearing. Same goes for the water pump except it will retain some resistance due to seal drag.

As for the flat pulleys that ride on the back of the belt, they get polished leading to a chirp , chirp as the belt slips / grabs as the belt walks across the pulley. A spritz of water will temporarily make this go away. The more permanent fix is to sand the surface with 80 grit. Even with this, I've had the hard smooth belt label make noise requiring some sanding to quite it down.

Continuous at startup and before the belt warms up, it'll also do it under acceleration.

I'll have to have my friend try that, he was finishing up the job since I had class today.

Before I was getting fraying on the back side of the belt (though I think that may have been related to the alternator I was using before) and the ribs were losing a lot of rubber. We'll run it for a while to see if it's getting the fraying still, if that's the case, I can replace the fan clutch bracket (with OEM), water pump (with Laso), and the crank pulley if that somehow got out of alignment. I'm planning on replacing the engine in this thing in about 6 months anyway with the one out of my 91K Sportline when I put a 3.0L in mine so it's really not all that important, I doubt this belt will fail between now and then as the last belt was still usable but worn after 15K.


This is probably the case, the fan pulley looks pretty shiny. This will be the first thing I test next time I have the chance. I know the fan clutch I have on it (Sprinter clutch with 606 blades) probably puts a decent load on it at startup.

Can you check the number of grooves on your pullys to those on the belt . Belts go by groove number. What i mean is- not all belts have the same number of grooves on them some 6 some 8 etc .