Geday from Australia!
My 1987 300D W124 (603 motor - non turbo) has a squeaky belt. There ain't much room to work in the front there, so I have to take off the fan.
For this job it is recommended all over to get a "fan pulley holder" and a short 8mm socket- both Mercedes parts.
Mercedes Australia (specifically Peter in Spare Parts Zetland Sydney in his high handed arrogant fashion) says "I don't sell tools." Wouldn't even listen to the part numbers.

Well bugger them then.
Does anyone know if I can...
a) cut off a 8mm Allen Key (to what length?)

b) for the "holder still-er" there is talk in some places of a piece of thick wire or whatever , bent to L - shape, and put through a hole in the fan pulley and into the block or timing chain cover (sorry not sure) to lock it. Does this work on the 603? Or do I need to clamp it from the circumference of the fan pulley??? If the "bit of wire" works, could someone give me the recipe to make it please?

Thanks in advance for your crazy home made solutions for getting that pesky fan OFF!!! (and back on)

Sorry can't help you much (have different clutch), but I have seen some pics, will see if I can find them.
It's funny that u mention merc. aust., I went into the local spare part department (run in conjunction with some other car brands), to buy some OEM sealant: Chassis number please! -> Me korean copy!
Went and bought Toyo stuff!
To merc's rescue I have to mention, that the local dealer gave me a lend of a RIV tool over the WE, for free!!

BTW, what makes you sure it's the belt and not the pulleys?

Cheers,

Kay

You don't need to clamp the fan, just hold it. I use a regular 8mm allen wrench, but on the W126 their is more room. You may either have to cut the wrench down or pull the radiator. The W124 is tight.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Although I haven't done it, I have read on this forum that it can be done with the fan in place.

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Gone to the dark side

- Jeff

Thats how we did it on my friends E300D, which has almost the same belt set up as the 603.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

There's no need to pull the fan to replace the belt. All you need is to release the belt tensioner. A lever and the appropriate wench will do the trick. A 12" 3/8 drive rachet extension serves nicely as the lever. I forget the wrench size, been too long since I sold my OM603. Probably 12mm or 13mm.

Just release tension, work the old belt off, work the new one on. Worst case you may have to drop the front sound encapsulation panel to get at the bottom pulleys.

- JimY

THANKS VERY MUCH for these awesome replies. I feel much more confident to attack this job now.

I must especially thank BillyBob for his excellent reply quoted below

"

The easiest way is the proper tool of course! But I use an old serpentine belt around the fan pulley, clamp it it place with vice grips and it forms a very effective strap wrench to counterhold the pulley in place! The 8 MM Allen head bolt is fairly easy to get out if you take a 1"X1/4" flat steel bar and weld a 1/2" piece of Allen wrench to it. The best way is to drill theexact size hole through the steel bar and then weld it from the backside leaveing the proper 1/2" protruding. The other method is to cut a standard allen wrenche's short leg so that only a little over 1/2"or 3/4" of the leg is left then you can get a piece of pipe over the long leg and turn it, I use the hollow steel handle from my hydraulic floor jack its heavy walled and about 18" long so it works perfect. The real trick is to get the Allen bolt's head very clean using carb or brake cleaner first, then get the allen wrench seated all the wat into the hole, the bolt has blue locktite coating on it so it takes some force to break it free. Once you get the Allen wrench seated correctly you can slack the serpentine strap wrench to rotate the fan pulley hub, its easier to do that that to reposition and reinsert the Allen wrench into the bolt head. Good luck! If you don't already know the tool kit lug wrench handle fits into the black plastic cam block hole at the top of the tensioner arraingment. You insert it and lever it a little to take the tension off the securing bolt that passes through the head. Take off the 13 MM nut, lever the cam block enough to lesson the force on the bolt and then push the bolt rearward enough to get it's end past backwards out of the plastic cam block, them you can completely release the tensioners force. If you simple replaceing the belt it can be done without removing the fan, you can just work it through the fan blades with the fan duct loosened.
"

thaks mate!

it was the bearing in the water pump (thanks Kay- you were right). The noise was exactly the same as a slipping belt.

So the radiator has to come out!

If your AC isn't working you may want to do like I do and that is pull the condenser so its a straight shot from the front. Makes changing the WP a snap. I left the mess off (condenser and fans) and I swear that '87 300D never ran so cool (well, the new radiator helped I'm sure).
I always replace the pulley if its old because the bearings are usually about to go out.
You need a large hex wrench or socket for the idler bolt then some loctite for the bolt when it goes back on real tight, what is it 45 nM?

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

So there is the noise coming from the area of the Serpentine Belt. I put lube on the belt and the noise stopped- for a short while.
Instead of ASSuming it is the belt- I should have used a stethoscope to listen around to various bits, and I would have saved much time and money and got it right first time.

Ok so my belt went out, time to replace. What an ordeal! I've changed many belts but never this difficult. There's no room to stick your hand anywhere. Today I spent the day reading through posts trying to figure something out but no go. The best advise I found was use vise grips.

Ok, got it on so here goes for everyone else having this problem.

Things I learned:
A: You can't put the belt on with the tensioner spring on the tensioner B:You can put the belt on without the spring but then it's impossible to put the spring back on by hand
C:The belt needs to be looped around the tensioner before and not last, the steering pump should be last.
(picture of serpentine belt setup)
D: You can only loop the belt around the tensioner from underneath the car



so what did I learn? If you've never done this before please follow along and you might want to print the pictures out.

1: The tensioner works like a "teeter-totter" pivot point in the midle, shock absorber on the left and tensioner spring on the right.
2: With a screwdriver or vise grips, pry the tensioner spring off. Becarefull it's under tension.
3: Place a medium to large flathead screwdriver between the water pump and lower shock absorber mount.
--3a: pry the tensioner absorber upwards leverageing against the water pump. Do not use excessive force. Just a steady slow pressure will push the absorber upwards, remember absorbers are made to reduce shock so it's nice, slow and steady until the oil passes through those little tiny passages it must have inside.
--3b: This will release the pressure both on the excisting belt to remove and allow you to wrap the new one around.
4: Loop the belt around the Alternator and Crank first, then the tensioner which by now should be sufficiently de-tensioned then the AC and last the steering pump which should be nearly impossible.
5: This is tricky and it's best to have a buddy applying pressure to that screwdriver-absorber bit as you pull the belt around the power steering and AC unit. Wrap everything so the only thing left is the power steering and do that last.

Now you have the belt on but no spring and no tension on the tensioner. This was the trickiest part. An hour of sitting on the toilet contemplating the problem gave me the solution but you'll need a special tool you may or may not have.

It's called "brake spring pliers" and It looks like two sticks of metal attached at the middle by a ribbet. One end has a hook and an arch. and the other is fairly straight with a hook. If you've ever done brake drums you know what I'm talking about because that's what it's used for. Hope this picture helps. Notice (on yours
not the picture) that one of the ends has a hollow groove in it. This is
to hook the end of the spring hook and create tension using a folcrum point.
6: Hook the tensioner spring back on the bottom of the tensioner (right side of the teeter-toter).
7: Gently push or pry down as far as you can on the tensioner. You wont get too far. You're trying to release or extend the shock absorber now as far as it will go. The more tension you can create manually the easier, or less the spring has to strech. You're pushing down on left of the teeter-toter so the right or spring side goes up.
8: Hook a pair of vice grips on the side of the top hook on the tensioner spring in case you have to grab it.
9: Hook the end of the brake plier handle with the hollow groove and hook to the peak end of the top tensioner spring hook.

10: USING THE TENSIONER LEVER (PART 10 IN ABOVE PICTURE) AS YOUR FOLCRUM POINT PUSH DOWN ON THE BRAKE PLIERS CREATING(STRECHING) TENSION ON THE SPRING. PUSH DOWN TO ABOUT THE 8 O'CLOCK POSITION OR AS FAR AS IT TAKES FOR THE SPRING TO COME ABOVE THE TENSIONER LEVER.

--IF YOU DID IT RIGHT, THE TIP OF THE BRAKE PLIER THAT YOU'RE USING TO STRECH IT SHOULD BE SANDWICHED BETWEEN THE TENSIONER LEVER AND THE SPRING.

11: Using the vise grips to secure the spring doesn't snap out of place, gently remove the brake pliers slowly and wala!

Good luck and hope this will help the next guy like me that couldn't find help.

Welcome to the forum.

While it's admirable that your tenacity allowed you to get that belt changed, there is ample information on the forum that shows how to do it with no specialized tools.

The key to success is not to remove the spring. If you look at the plastic bracket at the top attachment point, you'll see a large hole in the top. Using a suitable round bar, insert the bar into the bracket and unload the upper screw. Remove the screw and carefully release the tension on the spring with the round bar.

The belt is now loose.

Pull the belt forward and out around the fan.

Reinstall the new belt, starting at the tensioner and working all the way round the pulleys. Access from underneath is not required.

To tension the system, insert the round bar into the plastic bracket and tension the spring until you can insert the retaining bolt. Secure the nut and you're done.

The entire belt change can be done in 15 minutes.........from the top........with only the round bar to rotate the plastic bracket.

The handle of the lug wrench happens to fit perfectly...

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Yes it does!! In fact in the service repair CD and Manual MB suggests the use of the lug wrench.
The first time I replaced my belt, Itook off the entire spring, the radiator fan shroud, and fan. Then I realized that I really did not have to this, the belt is long enough to go around the fan. The second time I changed one out it took less than 15 minutes. You just have to do it once and then you will never forget how to do it.
But.... I do have a w126, and it is much tighter in there on a w124.
John

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John
1986 300sdl
1985 380se

I changed my alternator and serpentine belt yesterday. I wish that I would have read this before I started. Of cours I removed the spring. Needless to say, it took me over 3 hours. 2 hours and 20 minutes trying to retension the belt.