I want to replace the serpentine belt on my 300E but I have no instructions on how to do it other than a diagram of the belt and pulleys. It looks to me like I must first remove the shroud around the fan and then somehow loosen the tension pulley. However I have no idea how the pulley is loosened. Is there a bolt? A spring?

Please advise>

Smiles.

First of all you have to remove the fan and fan clutch. There's no way around this. On the tentioner there is a 19MM bolt to loosen and the the 13MM adjusting screw. Once you find these just loosen the adjuster screw and remove the belt and replace it using the diagram in your owners manuel or whatever instructions you have.

You will be able to change the belt by removing the fan shroud from the radiator, lay it over the fan. It can stay in the car. You should not have to remove the fan or fan clutch, unless you want too, but why would you want to do that. Loosen the tensioner as advised, you will then be able to remove the belt by taking it off the idler pulley, and follow with all the others. New belt should start on at the idler pulley and follow the routing diagram found in your owner's manual. Have a great day..

I'd like to learn this trick. It would save me alot of time and trouble..

Stan, visualize the front of the engine. You have to catch the crank pully which sits right behind the aftmost lip of the shroud. How I have done this is to pull the shroud off the radiator, lift up and lay it over the fan. Sometimes helps to remove cover on distributor. Loosen tensioner, remove belt from pulleys and work it out around the shroud. Same with replacement, work the new belt in over the front of the shroud and mount to pulleys ans so on.

Jeff,

My first attempt failed mainly because I cannot see much of what I am doing and I am hoping I have the right nuts or bolts.

I attempted your quick method. I pulled shroud up a little and then placed it around the fan blade and a couple of inches back from and off the radiator.

First I loosened the 19 mm nut that sits to the upper right of the tensioner pully. Then I feel and see a smaller nut to the upper left side of the pully. This nut is smaller than a 13 mm. It is a 12 or an 11 mm. So far no luck in getting it loose. Is it a standard threaded nut that simply locks the pully in place or is it an adjustment nut that moves the pully as the wrench turns it? Also what is the size of that small nut?

If I cannot get things loosened up this way.... how do I getthe fan and clutch off? The pully slips on the belt when I put the allen wrench into the center of the clutch. Is it right or left handed thread?

Thanks .

Earl

I've replaced an M103 belt without removing the fan, but this was on a car with a two peice shroud that could be removed from the engine bay without removal of the fan. Routing the belt was something of a puzzle, but starting in the tightest spot, between the fan pulley and whatever is at its 7 o'clock position (looking into the engine bay), was the key for me.

Since the tensioning system is new to ejsharp, I'll offer that the tensioner body has an indicator to help you set belt tension. On some cars, the indicator is a series of tick marks, on some cars, it's a triangle. There could be other indicator schemes. In any case, you want the pointer to move from US driver side to passenger side to the end of the marks. I think the pointer stays in place and the tensioner turns, but that's of no consequence. You set tension by tightening the 13mm tensioning nut. When tension is set, torque the 19mm head bolt on the tensioner.

And lay a sheet of cardboard or thick fabric over the radiator before a tool slips from your hand.

Sixto
91 300SE

With the fan, the shroud, the belt. the pullies and the radiator all blocking my view, I cannot determine how the bolts that I can feel and just partially see, relate to the tension pully. I can see and feel a 19 mm to the right of the pully and a smaller one to the left of the pully. Are these the two bolts being refered to?

Smiles.

Be Patient
 

Brother of The Benz, ejsharp
I've read your plight.
It is 2345 hrs here in Houston and I'm tired.
If someone hasn't helped you by to morrow morning I'll return.
You are being given some dangerous information and you could cause some very expensive damage.
Happy Trails Beep Beep from The Spiderman in Houston!!!

The 19mm bolt on the tensioner is the only 19mm bolt in that area so there's no fear of touching the wrong bolt. It's roughly between the idler pulley and power steering pulley, but it's not on a pulley itself.

Loosen this bolt two to three turns. Just so you can turn it by hand, and no further. You don't want it to come off!

The tensioning nut is on top of the tensioner. It points down into the tensioner behind the power steering pump. It's a hollow tube a couple of inches long with the top part shaped like a hexagon to accept a 13mm wrench.

The only indication that you've slackened the tensioner is that the tension indicator will no longer be at the proper position... assuming it was at the proper position to begin with, and the belt will be looser. It'll still be on there pretty good, but you'll notice it's not as tight.

You still have to wrestle with the tensioner pulley, the small one to the US passenger side of the 19mm bolt, which will now be relatively loose, to get the old belt off and the new belt on.

If you haven't replaced a belt on an M103 before, follow Stan's advice and remove the fan and clutch. If you don't know how to do that, let us know because it'll probably fill another page.

Regards,
Sixto
91 300SE

BTW, if this advice happens to work, it's because of what I've learned from folks like Stan and Jeff. The factory manual was of little help to me in this job, and I certainly didn't figure it out on my own. Doing it my way, if unconventional, has been good enough to keep an engine going without belt trouble for 14 months.

Sixto
91 300SE

Too Many Cooks
 

Brother of The Benz, ejsharp
I'm not sure how many instructions you'll need, but here's one more.
Remove the Ignition cover from the distributor cap.
Remove the 2 retaining clips holding the shroud in place and lift the shoud up from it's positioning slots.
Lay the shroud back over the front of the engine.
To remove the fan/clutch you will need a special allen socket wrench and an anti-rotating bar to keep the fan from rotating while you loosen the retaining bolt.
These can be purchased from many sources.
At the belt tensioner, loosen the 19mm headed bolt 1/4-1/2 turn.
Turn the setting pointer to the left and position it to the first graduation mark(arrow).
Remove the old belt.
Fit the new belt beginning with the belt in a "U" with the ribs or flat side in position.
1. position the "U" around the tensioning pulley and proceed in sequence
2. top of crankshaft under to the right
3. from the tensioning pulley over the fan down to the left
4. under the alternator pulley up
5. over the idler pulley to the right
6. over the water pump
7. around the power steering pump pulley
8. across the A/C clutch
9. finish at number 2.
Turn the tensioning nut to the right until the pointer is positioned to graduation mark 7 with A/C or 5 w/o A/C.
Tighten the 19mm bolt to 75Nm.
This presets the automatic belt tensioner.
Replace the removed components and you're finished.
I know this is long winded, but it will keep you from making a mistake.
Happy Trails Beep Beep from The Spiderman in Houston!!!

When you're done, put your old belt in your tool bag in the trunk of your car and make sure that you have the 19mm and 13mm sockets there just in case you have to change it on the road some day.

I had to change one in a parking lot. It was a quality belt too, with only 15K miles on it...

I actually keep a NEW belt in my trunk now. That way, if it ever happens again, I don't have to put my old, used belt on just to get home and then immediately change it again for a new belt. Also, the fact that I now have a new belt on hand gives me additional incentive to change it at the first sign of wear.

Changing belt at same time as radiator,any advantages/modification?
 

if I want to do a R & R on the serpentine belt while changing a radiator with a repaired neck,are there any modifications of the below technique,or is it the best time to do it?

What brand does the Fastlane sell(belt,I mean ) or should I get a real MB stamped belt?

I believe the belt that fastlane sells is Contitech and is the OEM belt.