The 240D I have been driving likes to squeal off of every stop I hit and I'm just wondering if there is a specific belt dressing I should get for it. Thank you.
I'm also not quite sure if I posted this on the right discussion, I'm new

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Usually the belt needs adjusting or it is shot in some way. For a temporary way to restore traction on a belt. I just use a bar of soap rubbed onto the belt.


As a general rule though something other than a belt dressing is indicated with a squeeling belt.

Adjust your belt tension and/or replace your belt.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Okay, thank you. Do you just use a regular bar of hand soap for it or?

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Belt dressing will make things worse, it goes on wet then drys to a gloss that is semi slipery.

Soap might make it quiet but won't fix a slipping problem , don't use it.

Properly tighten the belt + replace it if cracks are appearing.

Actually if a car in the day developed a squeal when far away from home with no tools. Using just bar face soap rubbed on the vee portion of the belt stopped it. Did not see any issue with charging. Actually the initial squeal is usually because the alternator is perhaps being asked to produce more current initially. Or is resisting acceleration. Logically you would think it would be worse with the soap for slippage. Glycerine may be a rubber softener. Anyways this was not considered as a permanent fix. Usually I adjusted the belt at the first opportunity. Or did what was required.


Also rather than belt cracks because these cars may have sat for some time.I guess this depends on the region you are in. I am in the rustbelt.


I have found that any rust on the pulley surface where it contacts the belt. Can reduce the belts cross sectional area. So clean it up if present. Basically the pulleys are eating the belts.


I do not think this is created by a loose belt. More perhaps as the belt lifts out and enters the pulleys. The rust is abrasive to the belt rubber. Another thing to watch out for is a belt that has just worn down and is hitting the bottom of the vee in the pulley. Or cracks on the inside of the belt indicate the belt may break as mentioned in an earlier post.

All belts should be inspected for cracks and wear periodically.


Belts also stretch a little in initial use.I have found that I have had to retention them tighter again not long after installation many times.


I think it was a 240 of mine. I got the right belt I believe. Or at least it was supposed to be. To me it was running too deep in the pulleys. So I just went out and selected a good sae sized utility belt that had a larger cross section. The top of that utility belt was level with the top of the pulleys.

Try using the belts from the dealer. They aren't that much more expensive and aren't toothed. I used Continental for years thinking they were OEM, they are, but you'll get the toothed belt which isn't. The smooth belt from the dealer are Continental, but no teeth.

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Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

Take a good look at the alternator and crank pulley to see if the grooves are worn.

Belt dressing is supposed to soften the rubber usually with sort of a solvent action. There is a rubber cement type gasket cement called Gasga-cinch. NAPA sells there version of it. Besides the use for gaskets it also has belt dressing.

As the other said belt dressing is entirely temp. Better to get to the source of the problem.

Note that a former owner may have used US sized/widths of belts. Which of course can wear the pulleys in the wrong places.

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84 300D, 82 Volvo 244Gl Diesel

And make sure the pulleys are aligned and not damaged

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

It was good of a poster to mention pulley wear. That could have been an issue of why I landed up using an sae belt. To get a better width or cross sectional fit .


Some of these engine pulleys might have a gazillion miles on them. For example that engine I did this on was a factory rebuilt. I do not know if an automatic pulley change was done. During the rebuild.

PepBoys sells belt dressing in a spray can. Has a plastic tube like on a WD40 can. Works fine but probably just masks the real problem.

When I have had a constantly noisy belt, I used a squirt bottle and sprayed plain water on. If the noise goes away briefly, I would first check tension and belt condition. They are usually OK! Can't tell you how many used belts I still have that look in perfect condition.

I too bought belt dressing in a spray can (Canadian Tire). Very inexpensive. It doesn't actually spray, it discharges a thin long stream of dressing. This makes it easier to get it to where you want it. Once applied, I found it worked for at least 3 or 4 months.

If belt only squeaks on startup, I would check tension. Not too loose and not too tight. Then give belt some dressing anyway! PS often was culprit on my old cars.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5