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91 500SL 37k,90 300SE sold, 91 300E sold , 92 300E137k ,02 Kia Sedona ,I know..... its a Mini van.
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Discussion Starter #1
Hey enthusiasts ! been a while, cars been running great, but....... now my son's 1992 300E has a issue with belt squealing only with A/C on, that's what he's complaining about.
So car is at 140K miles now, I just checked under the hood and all pulley's are straight and true while running, with A/C on no belt slippage at idle or revving engine.
Took it for a test drive and I hear a loud squealing like belt slipping only with A/C on and giving it some gas going up hill, pretty bad when its changing gears.
Belt feels OK and tension seems OK also, last year I changed water pump, tensioner etc.
I think I replaced belt 6 years ago.
Going to get a new belt anyway.
Here's a picture of adjustment arrow on tensioner, how's this look to you?
Thanks John!
2639020
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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Well John, being you first question is whether that is a URO tensioner? 馃槈
 

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Current, 90 300CE, 92 400E (Sold 95 E320,70 250C, 91 190 2.6, 91 420 SEL, 95 300D, 87 TD)
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I've noticed the automatic tensioners rubber deteriorates after a short. Maybe a year or two. I don't even know if it's genuine Mercedes part will work any better. I think it totally depends on when the part was actually made.

If the part was made a long time ago rubber can still deteriorate.

I had a automatic tensioner go out on me a year after I installed it (wouldn't hold tension when I took it off it's spun all the way around) and the belt was squeaking. Granted I think the replacement part was a Mayle brand. .... Before I knew Mayle was a cheap Chinese part. (I knew about uro brand but I didn't think maybe was in the same category at the time)

I know I'll probably get ripped on...(he he;))...But I modified mine (400E) with a bolt (I drilled all the way through the rubber and tapped the opposite side,then screwed the bolt in, then ground off the bolt head (bolt head adjustment interference) end so I can manually adjust the tension.

No slipping for several years now! I engineered this solely for the reason that I didn't know how this was ever going to stop. And if there was a part out there that would work properly.

Honestly if I thought I could get one that would work I probably wouldn't have done any of this.

But it's been working so haters hate!
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,229 Posts
the manually adjusted tensioners aren't 'automatic', and they do wear out but its more like 20 years for the OEM one. the give-away its shot is when you release it to remove the belt, it doesn't return to the original position, and if you take it off the car you'll note the 'flats' ont he shaft aren't pointing at hte pulley.



since this is a once-in-20-year replacement, I'd be sure to use a real Mercedes part, and not any clones.

mid year 1995, they switched to an entirely new tensioner design, that has no adjustment, and uses a spring instead of an elastomer. these should be lifetime. but to retrofit this on the older cars requires a different pedestal mount for the hydraulic power steering or tandem pump.
 

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91 500SL 37k,90 300SE sold, 91 300E sold , 92 300E137k ,02 Kia Sedona ,I know..... its a Mini van.
Joined
8,150 Posts
Discussion Starter #5
Thanks guys, hopefully just needs adjustment or new belt, I put a new one around 7 years ago when I did the head gasket, replaced water pump recently and installed Meyle Belt Tensioner Adjuster and belt tensioner assembly, looking at my orders from AutoHauz Az it was 2017 .
It doesn't feel loose or anything, I can punch it with A/C off and no slippage sounds at all, I was thinking maybe the A/C compressor clutch is having issues??? its original .
I'm going to try the easy stuff 1st lol.
My son is finally working and loves his job and saving money, He wants me to fix it but car needs more work, oil leaking from HG is nasty, new muffler, new oil sender, paint is starting to peel, so he's going to fund any fix's or buy another newer car.
But the car drives fantastic! did a lot of suspension work years back and its rock solid, such a great handling car.
I also need to know, do I have to wear a face mask while working on the W124?
 

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91 500SL 37k,90 300SE sold, 91 300E sold , 92 300E137k ,02 Kia Sedona ,I know..... its a Mini van.
Joined
8,150 Posts
Discussion Starter #6
Well I tightened the belt a tad and its all good now, tensioner is working,drove the heck out of it uphill with A/C on and quiet when shifting gears, belt probably stretched a tad, will replace it when I pull the head.
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
Joined
7,229 Posts
if when you RELEASE all the sensor tension (after loosing the locking screw), if it doesn't return to the far end, THEN you know the elastomer has deformed.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,495 Posts
Are you sure the A/C compressor isn't starting to seize up?
 

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91 500SL 37k,90 300SE sold, 91 300E sold , 92 300E137k ,02 Kia Sedona ,I know..... its a Mini van.
Joined
8,150 Posts
Discussion Starter #11
I was thinking that also, seems it would squeal or lower RPM's big time while cycling on and off? did not see that issue manually revving it in the driveway, symptom was squealing in between gear changes while going uphill,we have a lot of steep hills here.
I crawled under to have a look see last night, expecting to find a grimey oil coated compressor , but it was super clean and no signs of leakage.
 
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