With the onset of cold weather (I think it is related), I have picked up a belt squeal with the AC drive belt. Symptoms

Climate control on - Compressor off - squeal
Climate control on - Compresson on - squeal
Climate control off - no squeal

All belts are about a year old as is the idler pulley. Belts are at the proper tension, I would greatly hesitate to make them any tighter.

Anyone run into the same or similar symptoms.

Thanks in advance,

JCD

PS: Turbodiesel, good to have you back

I cant imagine why you would have a drive belt squeal only when the ACC is on, whether or not the compressor is engaged. The only ACC-related item that would put added load on the drive system resulting in drive belt squeal is the compressor....nothing else. The only other components that are engaged by the ACC system are mono valve, elecronic control unit, blower, vacuum switches (for flaps), and the aux. water pump. None of these put a load on drive belts. Of these, the only thing that can squeal is the aux. water pump..not a belt squeal, but squeal due to motor bearing or pump housing. I think that the aux. water pump functions at idle rpms, ensuring adequate coolant flow to monovalve/heater core. I suspect that your squeal happens only at idle, and is from failing aux. water pump...this is the thing mounted in the engine compartment just in front of the pass. side wheel hump.

Use the broomstick stethoscope method...take a broomstick handle, dowel or other piece of wood and put one end on your temple bone and use other end to probe for noise sources...i bet when you touch aux. water pump, you will know that this is the problem. (maybe not, but thats my best guess)

If this is the problem, fix it soon, because if it fails in a mode that causes very high current draw, it can fry the ACC pushbutton unit.

If this is not the case, give more info....squeal only at idle? also at highway speeds? are you positive about no relation to compressor?

good luck

mark

__________________
1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

Thanks Mark,

Squeal occurs during take-off, either from a stop light or in the wonderful stop and go traffic we have here in NJ.

At take-off, there is a belt squeal until shifting into 3rd gear. Then it stops.

It will also squeal when parked, if I rev the engine.

Again, I am 99% sure that it is a drive belt squeal for the AC, and it only occurs when the climate control system is on.

Jim

Evidently this issue is temperature related.

It is above freezing for the first time in a week, at least during my drive time. Took a spin up to WallyWorld and no belt squeal.

Huh

JCD

Greetings Jim,

If you have the York type compressor with the upper idler pulley then it is highly possible that when the compressor is engaged the lack of lubrication on it's center bearing may be your cause of squealing when loaded down by the a/c

Charles

__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan

Can-do,

Do you mean lubrication on the idler pulley. If so, I think you may be right. I ran a few errands today and no squeal. I let the car sit outside for a while, as I put the plow on the garden tractor, snow on the way.

While I was working, it got much colder, and when I got deployed to the movie rental and grocery stores, the squeal.

At this point, I think it is the idler pulley. I can see where the belt is frayed a little, which tells me that this is the belt that has been slipping.

I'll look at again tomorrow, but at this point I think I am going to try some belt dressing as a short term fix, and order a new belt and idler pulley.

If that's not it, there may be something in the compressor that doesn';t like the cold weather.

JCD

jcd - I have the same symptom in colder weather there is a
squeal when taking off (warm engine) then disappears after shifting to third. Sprayed belt junk on and seemed to help situation. BTW this is in extremely dry / cold conditions we have had lately. Will see what happens when the snow/rain comes!
Also thought it mite be the upper pulley as well ...

__________________
1984 300D Turbo - 231k....totalled 11/30/07 RIP

After thinking/looking/obsessing, it may be the compressor.

Any issue with disconnecting the lead to the compressor so it stays off.

Confused as ever,

JCD

Greetings JCD,

If it is in fact the upper pulley, metal one that is. This one can be disassembled down quite a bit and I had luck relubing it. The area where the bearing sits has a light weight cover almost totally covering it. I managed to clean out this area and relubed with high temp motorcycle chain spray lube. This stuff doesn't sling off where you put it, and has been working fine since June when I did it. If it's the plastic designed idler pulley, I doubt if this procedure will be a long term fix because when they start acting up they are already beyond decent repair.

Charles

__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan

Greetings JCD,

If you have a York compressor then the wires simply go up to a block. The Delco compressor has a connector but If it were me I'd just pull the wire off the freon pressure switch instead. The one on the Delco compressor seems to get brittle with age and may end up breaking during the unplugging.

Charles

__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan

I have a York. I can disconnect it easily with no breakage issue.

For me, I would have to add another line to your signature,,,,

"and for help, go to Mercedesshop.com"

Turns out it was the alternator belt. Tightened her up last nite and squeal gone. What threw me was until last nite, it would only squeal when the Climate Control was on, and stopped immediately when I shut it off,,,,even in mid squeal. I was "finally" able to get her squealin' in the garage so I could see/hear what it was.

Quietly yours,

JCD

PS, Although fairly easy and quick, tightening this belt was definately a 2 person job, at least for me.

I also had a squeak I couldn't figure out. Happened suddenly last week when it got REAL cold and snowy here in Atlanta, GA. Everything still worked fine, it only squeaked when I would start to accelerate, then it went away quickly. Then it would do it again the next time I would stop and start. I bought some belt dressing spray at a nearby auto parts store that same day, sprayed generously, and it hasn't happened since. The weather has also warmed up, so I don't know how much effect the weather vs. the spray had on it. Oh,well..it's gone, and everything still works, so I'm happy.

Mike

__________________
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1979 300 SD
350,000 miles
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1982 300D-gone---sold to a buddy
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1985 300TD
270,000 miles
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1994 E320
not my favorite, but the wife wanted it

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