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2008 CLS 550, 2007 SLK 350, Porsche Cayen Turbo S, Maserati Quatroporte Sport
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Discussion Starter · #1 ·
can the serpentine belt be changed by regular guys like us...or does it need to be done by a pro? If we can do it ourselves can anybody point me to a procedure? Is it like changing it on american cars?

Thanks-love this forum!
 

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Super Old Fart Moderator
2002 ML320, 2005 S430 4MATIC RIP, 2010 F150 Crew Cab
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11,788 Posts
If your hood doesn't have a routing diagram, make one before you start. Place a box end wrench of appropriate metric size on the bolt end of the spring tensioner pulley and release the pressure and slip the belt off with the other hand. Replace new belt by putting it on all pulleys before the tensioner, release tension by holding the pulley back with the wrench and slip new belt on. You may want to try releasing the pressure a couple of times to get the feel of it.
 

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1922 Ford T no OBD, no ECU, no SCN
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37,854 Posts
Same topic goes in 210 section, that shares the engine.
The tensioner has big hex for pulling the tensioner out and smaller center bolt is locking it.
You need a long box wrench to take the tension off and than you can slip the belt off. I think for easier job you can pull the tensioner out and lock it in this position with smaller bolt, what would leave you 2 hands to deal with the belt, but I never actually tried this method. Sizes wary supposable 13-17 mm for tensioner and smaller bolts come with different sizes and shapes.
 

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1999, ML430
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56 Posts
This is a really simple job. It will take you longer to get the right socket heads selected than it will to put the new belt on (my original has a Torx female but my new one was completely different). If you have the original idler pulley with over 100,000 miles, I predict the idler pulley bearings are rough and noisey (spin the idler puller once you have the belt off). My tensioner bearing also starting making lots of noise a few hundred miles after the new belt was installed. The bearing was clearly into failure mode.

Removing the single nut (36mm) holding the fan to the fan clutch is fast and makes the belt replacement, tensioner and idler pulley a breeze (in fact on the ML430 you must remove the fan to get the idler pulley bolt out). This is intended to be honest input AND sort of self promoting since I have an extra 36mm thin, long wrench I'd love to sell.
 

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Outstanding Contributor W221 Moderator
2010 E350 P1/P2, 2008 S550 Designo, 2002 ML320
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2,565 Posts
So I went to change my belt this weekend and found that the bolt through the center of the pulley is a Security Torx head (see picture). Does anyone else have this? If so, do you remeber what size it is? I hate to buy 12 bits when I just need one.
 

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2002 ML 500, 1994 Ford Explorer donated to Doctors without Borders
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2,126 Posts
Go on and buy the set. You know you will be happy to know that you have them all and can spend the next month looking for a use for them.

Seriously, how much is a set?
 

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Outstanding Contributor W221 Moderator
2010 E350 P1/P2, 2008 S550 Designo, 2002 ML320
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2,565 Posts
Well firstly, thanks for the bitset. There is a HF not 5 miles from me.

Secondly, this bolt is indicated as #4 in your diagram above. For my '95 S420 it is a male torx bolt, which I have a socket for. But for this thing it is as pictured below. Any thoughts?
 

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1922 Ford T no OBD, no ECU, no SCN
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37,854 Posts
Wait. There must be a reason why it is safety bolt. That doesn't look like tension mechanism. Might be just the rerouting wheel. It looks quite different on my 99 and 01 engines.
I am not familiar with your set up, but if you are not sure what is the tensioner, push the belt where you can and see what pulley will move. That would be the tensioner. Your picture is dark, but there might be spring mechanism behind the wheel.?
 

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Outstanding Contributor W221 Moderator
2010 E350 P1/P2, 2008 S550 Designo, 2002 ML320
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2,565 Posts
I will take a look tonight and see if this moves with increased belt tension.

It does seem odd that they put a security torx bolt in this location, as if we are meant to pry in another location. I'll try to pop the engine cover and look behind it, and post some pics of course. Thanks!
 

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Outstanding Contributor W221 Moderator
2010 E350 P1/P2, 2008 S550 Designo, 2002 ML320
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2,565 Posts
That is IT! Thanks so much NorCal!!! :thumbsup: :bowdown:

I ordered the tools to remove the fan and will try this out this weekend after they arrive.

BTW, glad I didn't order the bit set yet. ;)
 

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10' CX-9 GT-AWD, 03' e39, 98' ML (gone but not forgotten)
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dlafever said:
That is IT! Thanks so much NorCal!!! :thumbsup: :bowdown:

I ordered the tools to remove the fan and will try this out this weekend after they arrive.

BTW, glad I didn't order the bit set yet. ;)

you don't need to remove the fan to remove this tensioner, just craw under the truck and turn the tensioner from under. there is plenty of room, no need to remove any fan or any other parts if you only need to change out the tensioner or the belt.
 

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1922 Ford T no OBD, no ECU, no SCN
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37,854 Posts
That's a good question. We have 9-years old belt on at least one of our MB and it doesn't look too bad. When you see cracks on the surface, that would be the first sign, but telling the truth, I had V-belt with some serious crack on my tractor. I bought spare one when I noticed that, regardless 6 years later the cracked belt was still on the engine.
My personal advice is, that if you don't know how to change the belt, have it done every 50-60 thousands. If you know how to do it, buy one at 70.000 and carry with you. You might not need it in the life of the car, but risk of getting strangled in the middle of dessert is too high.
 

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Outstanding Contributor W221 Moderator
2010 E350 P1/P2, 2008 S550 Designo, 2002 ML320
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2,565 Posts
It's 108F here today, I'm changing it while it is still in the garage, not on the side of the road. :)


Change successful, no need for special tools. Thanks for all of your help Kajtek1, NorCal and supradupe. I changed it from below and it was quite easy.
 

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2000 ML320
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355 Posts
Great info, guys.

I was so inspired that I just changed my 8 yr old belt. My tensioner has a male torx fitting at the center (used a 3/8" breaker bar and e-torx socket working from underneath to loosen the belt).

This really is a five minute job once you figure out the belt routing (can't speak for a car with a v8). Also, I'll be keeping the old belt for a spare; it looks fine.
 
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