my serpentine belt broke, luckily i thought, at a gas station with a garage..i was in the middle of nowhere getting gas and it broke. Ive been busy of late, so a diy job just wasnt in me for what i thought to be a relatively simple job of replacing the belt; let the mechanic with tools do it.

i got the belt from the a part dealership ($40 can). I also got some insturctions and tips from this site after searches, and printed them up for the mechanic, basically stating to remove the fan with 2 allen wrenches, and to turn the 19mm ttensioning screw to drop the tensioner pulley etc; photocopied the manual with the belt path; i also said that the tensioning unit was prone to failure, but dont worry about it if it does, we'll take it one part at a time, one day at a time.

so i go to get the car; the owner is gone; his emplyee said that the owner was afraid to work on the car becuase it was a foreign car. I asked what to do, he said to tow to someone who would work on the car...

bizarre! hey, at least he knows his limitations. i gues its a diy job now. oh joy oh bliss. to avoid a tow, anyone know of a way to jury rig with a shoelace the alternator, power steering and water pump to the crank pulley?

I don't blame the guy for not wanting to work on the car; I wouldn't take the liability either. But what I don't understand is why you don't just go down there and change the belt yourself (it's cake). Don't take this the wrong way, but this thread hits me the same as if you were posting a similar situation with a flat tire. Get inspired and go down there and fix it yourself! You can do it!

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1982 Mercedes-Benz 300CD
1982 Mercedes-Benz 240D - stick

Changing this belt is not the most difficult thing I've ever done, but I wouldn't call it "cake." Changing this belt is actually a PITA compared to most other cars with serpentine belts.

You have to loosen the large center bolt on the front of thensioner and then loosen the tensioner with the long adjuster bolt/nut. You will most likely have to remove the fan which if you don't know how to do it, this in itself would fool a lot of service station guys.

This is not a 123 car with conventional belts. For many DIYers this would be a challenge.

Good luck,

Maybe it's just from my years of replacing thrown VW pulley belts, but I didn't find the W124 belt replacement much of an issue...if you didn't have to fool with the tensioner (which I didn't)

Was replacing the alternator, so I decided to throw on a new belt anyway.

You can "coax" the belt onto the remaining pulleys with a flat-tipped screwdriver. The belt is fairly wide, so as you help the belt along the different pulleys, rest the belt onto the screwdriver shaft and it will fall onto the last pulley.

Took about ten minutes to do it this way...most of which was figuring out the path...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

Not an easy DIY job with the tensioner.
A friend of mine used a bunch of Plastic ties to rig the water pump. Thats all he needed to get home.The car will run without the alternator. You will have no power steering and I would go easy on the brakes.

OK, maybe I shouldn't have called it "cake". IMO, any job that takes less than 30 minutes with a 100% success rate is cake, but I understand that a lot of people think changing the batteries in their TV's remote is a PITA. I still think that armed with the instructions from this site, as he posted he was, he would be successful doing it himself. The tensioner on our F350 is a mother to wrestle with, and we have to change that belt every year because for some reason they start squeaking. Anyway, I apologize for calling it "cake" as I realize doing so does not respect the different levels of DIY'ers here, and I certainly meant no harm to anyone with my attempt to inspire.

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1982 Mercedes-Benz 300CD
1982 Mercedes-Benz 240D - stick

I agree with G-Benz' procedure.

I don't even mess with the tensioner, for fear that it will fail to tension when I try to tighten it back up.

I don't use GB's screwdriver method but I pull the belt up over the very top pulley, after it's been set on the far left and right pulleys. The belt length from these two points allows some leverage in getting the belt up onto the last top pulley. (fan clutch?)

Belt has plenty of tension with no slips doing it this way, and I've had no problems with this technique FWIW.

Good luck!

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-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

I recently replaced the alternator in my 300E and I didn't have to mess with the tensioner either. I imagine that the entire belt could be replaced in a similar way. Removing the alternator is dead easy - two bolts.

To quote myself...

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Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

I personally would not even DREAM of forcing a belt into place like that. Yes it probably does take me less than 30 minutes, but it is not a snap of a job as compared to many other cars.

The first car I had with a microgroove, serpentine belt was an '85 Mustang GT 5.0. All you needed was a large screwdriver and put it in a slot that allowed you to release tension and peel off the belt. I probably changed that belt in two minutes.

Compared to that, the 300E belt is a PITA.

Out of curiosity, how long do your belts last after forcing them in place as you describe? It might be a pleasant surprise for me because I know that these belts are very durable. I guess that's because I put the software in place in a plant where they made them.

Have a great day,

Do yourself a favor - tow the car. Don't even think of any band-aid approach. The problems you could create could end up costing you a bundle.

This isn't a tough job if you have good documentation and the correct tools to loosen the fan bolt and the rod to keep the fan pulley from moving.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Thanks for the responses! Some of you are quite emphatic about diy jobs, so again, thanks for the morale boosts. In this case, my work schedule got quite busy and the days arent long enough yet to really get into an evening attempt.

For various reasons, i had to rent a car yesterday, a cavalier. what a difference, the seats on the cav were made to not support your upper back, the steering was over-responsive like a hair trigger, its ride was very light yet lacked the road feel one expects from a compact. I stopped by the 300e to try to put the belt on, and it was like coming home: the exterior and interior, even after 16 years, simply looked better.

Ok, got the fan shroud off. how does one get the fan off? ive got a 3mm allen key, an 8 mm allen key and a 8mm hex; i tried a few things, then it got too dark to really continue; I tired to route the belt without taking the fan off, but my knuckles paid the price; whether one takes the tensioner off or not, i think that fan should come off.

Also, excuse my igonroace, what is PITA? an acronym obviously, but my attempts end up using foul language.

PITA stands for "pain in the a$$"!

I haven't done this job for awhile, but I think you need a 7mm allen to remove the fan. There are three allen bolts that you access from the inside of the fan housing.

Once the fan is out, there is a lot more room to work with...

Replaced the belt in 2001...still holding.

As archaic as I am with repairs, I am extremely careful and patient. So I rarely break things as I proceed...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

HOw about calling MBZ road side assistance. Do they have them in your area?

My Dad has used them for all sorts of trivial stuff and they are not that expensive. He had them come by to jump start his 230SLK, then they told him his battery was bad and they sold him a battery in the spot and installed it for $125. Not bad considering he waited for them at his house sipping a tank and tonic.

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63 190d (sold)
69 220D (sold)
69 280SL (sold)
76 BMW 2002 (sold)
86 190E-16v (Demised at Laguna Seca Turn 9)
87 300SDL (sold)
87 300SDL 135k
87 300TD 280k (sold)
95 E320W 211k
95 E320w 111k
05 C320 4matic
06 E320 CDI 90k (Totaled by a texting 19 year old girl in a nissan)
2013 GLK 250 Bluetek 4MATIC

To remove the fan you will use the hex key on the outer four screws that attach the fan to the fan clutch. You will have to keep the clutch from turning while you do this. There is a special tool for this, but it is nothing more than a bent piece of rod about 1/4" in diameter. There is a slot that you fit the rod into on the engine behind the fan, then it locks into one of the reliefs on the fan clutch to keep it from turning while you loosen those bolts. It's very difficult to describe with words.

Good luck,

Mission Accomplished! Thanks for the advice from all.

The alternator method, suggested by Zues, is the best way to tighten the belt, if your older 1988 m103 has a tensioning pulley that you suspect will fail if moved.

this is how i did it:

1) disconnected the plastic rad shroud by removing two clips and draped the shroud over the fan blades; it will not come out

2) removed 3 screws using a 5mm allen key on the front of the fan blade; they were placed on the fan like a 3 point star (like the mb logo?); i simply held the fan balde as i turned the screws; i also wd-40ied them before cranking them off. This was the hardest part of the job. The shroud can come out, but i had to rotate it a few time to get it to do so PITA; maybe it neednt come out.

3) route the belt, leave slack around the alternator.

4) remove bottom alternator bolt; loosen top bolt if the alternator wont budge; lift alternator tand get the belt on; push down on the alternator - it seems to act as a natural tensioning fulcrum. Install bottom bolt - BOBs YOUR UNCLE!

i had a minor problem getting the alternator to slide back into the bottom mounting posts, as the increasing tension warped the alignment of the alternator as it moved back into poistion: i tightened the top bolt which nearly re-alligned it and also held it, under tension, in position. i then put a very very small bend in the bottom post flange enought to let it slip past, then bolted it into position. if you have a helper, one can push the alternator down, while the other uses a crewdriver or tool to nudge the mounting post a "smidgee" and let the alt pass.

so far so good