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Self-tapping bolt, belt tensioner to timing case cover, thread not pre-tapped Nm 35 or thread pre-tapped Nm 25
Shock absorber, belt tensioning device to belt tensioning device Nm 25
Shock absorber, belt tensioning device to coolant pump housing Nm 35
Self-tapping bolt, belt tensioner to timingcase cover, thread not pre-tapped Nm 35 or thread pre-tapped Nm 25
The tensioner is #4 in the photo. The two bolts that hold it in place are torqued to 25Nm (about 18.4 pounds). Sounds like I have it wrong. Using the photo, which bolts are being over torqued? Or have I got the whole thing wrong and there's another part with other bolts?
Last edited by MarcusF; Sep 5, 2013 at 03:52 PM.
Reason: corrected Nm to lb-ft conversion
Unfortunately, the prior picture, does not show the Idler Pulley (a.k.a. Guide Pulley).
Enclosed are 2 additional pictures.
The Idler Pulley is 2.5" plastic pulley, that is attached with a single bolt, through the bearing race (using a T50 torx bit).
I suspect that using 25Nm (a.k.a. 18.4 ft-lbs) of torque, is to much (e.g. I've read of several instances, where the bolt sheared off inside the bolt hole).
If you can find the factory torque specification for this bolt, it would very much appreciated.
PS: Failure of this pulley has been a common problem (e.g. overtime, the plastic develops fractures and self destructs, causing an untimely/expensive breakdown). Since an OEM replacement is less that $20, decided to replace it and for good measure, with the new updated belt tensioner and new serpentine belt, as well.
Last edited by Serndipity; Sep 7, 2013 at 06:30 PM.
Unfortunately, the prior picture, does not show the Idler Pulley (a.k.a. Guide Pulley).
Enclosed are 2 additional pictures.
The Idler Pulley is 2.5" plastic pulley, that is attached with a single bolt, through the bearing race (using a T50 torx bit).
I suspect that using 25Nm (a.k.a. 18.4 in-lbs) of torque, is to much (e.g. I've read of several instances, where the bolt sheared off inside the bolt hole).
If you can find the factory torque specification for this bolt, it would very much appreciated.
PS: Failure of this pulley has been a common problem (e.g. overtime, the plastic develops fractures and self destructs, causing an untimely/expensive breakdown). Since an OEM replacement is less that $20, decided to replace it and for good measure, with the new updated belt tensioner and new serpentine belt, as well.
You're right, I got the Nm to lb-ft conversion all wrong in my last post.
Per the WIS, the spec for the idler pulley bolt is 20 Nm (14.75 lb-ft). The WIS shows the bolt as an M7x25. One option is to buy another bolt and use the new one when replacing the pulley. A hardware store or machine shop should have a replacement at very inexpensive rates.
Don't think I'll easily find the required M7x25 bolt. The head size, shape and length must properly fasten the pulley's bearing race onto the timing cover cast shoulder w/o bottoming. It's pretty long and on CLK V8s, part of the radiator housing must be removed for clearance as well.
FWIW, I found the Chrysler Crossfire (CLK drive train on a SLK chassis) shop manual online. Their suggested torque for the Belt Tensioner bolts is 14Nm (vs WIS 25Nm), the Idler Pulley is 10Nm (vs WIS 20Nm).
At this time, think I'll slightly under torque per WIS along with some thread locker.
Last edited by Serndipity; Sep 7, 2013 at 06:29 PM.
14Nm is definitely the correct torque for all three bolts. I have just now replaced my belt, tensioner and idler and the three bolts are very small diameter. 25Nm and you will definitely strip the female threads and then there will be tears.
At 170 000kms the bearings on the tensioner and idler were very dry and noisy but the belt was still in excellent conditon.
While I tend to agree with you........as your numbers are much the same as the Crossfire specifications of 20Mm (vs WIS said 25Nm) on the 2 tensioner bolts and 10Nm (vs WIS said 20Nm) for the idler pulley bolt and appropriate to smaller fasteners.
How did you determine that 14Nm (10.3 ft-lbs) are the correct torque requirements for both the tensioner and pulley bolts?
Last edited by Serndipity; Sep 7, 2013 at 10:48 PM.
I suppose the X fire guys learnt from bitter experience as these are very coarse threads and so easy to strip the aluminium female thread on the engine casing.
WIZ is 25Nm for tensioner bolts and 20Nm for idler, so lets just say 20 and 15nm
As a follow-up, new Idler Pulley, Serpentine belt and updated Tensioner are all installed and well.
The torque specifications, for a W-208, as supplied by Marus are correct (see below).
TORQUE SPECIFICATIONS
DESCRIPTION--------------N·m-------- Ft. Lbs.
Idler Pulley Bolt-------------20----------14.75
Belt Tensioner Bolts---------25----------18.44
Note: It's only on vehicles equipped with a supercharger, where there are specific components that require lower torque settings when replacing (e.g. the additional supercharger idler pulley / bracket).
Last edited by Serndipity; Sep 10, 2013 at 08:26 PM.
As I posted above, failure of the ider pulley has been a common problem (e.g. overtime, the plastic develops fractures and self destructs, causing an untimely/expensive breakdown and sometimes other collateral damage).
Since an OEM replacement is less that $20, decided to replace it and for good measure, along with the new updated belt tensioner and new serpentine belt.
Turned out to be the right decision, as the original pulley had developed 3 cracks (see enclosed picture).
Note: the cracks usually develop on the engine side of the pulley, which is not visible.
Hint: You can check this pulley (or replace it if necessary) by only removing 1 bolt and taking tension off the belt (e.g. very easy and will take less than 5 minutes)..
As added insurance, I also replaced the serpentine belt, as well as the belt tensioner with the updated redesigned unit.
After 83,500 miles, the belt was in great shape however, when I hand spun the old tensioner, it was starting to develop some bearing noise (e.g. still inaudible with the engine was running).
Last edited by Serndipity; Oct 1, 2013 at 03:41 PM.
E55 AMG V8 Kompressor 2004 E 55 AMG Type: 5,439 cc (5.439 L; 331.9 cu in) Supercharged V8 Powe
Good thread thanks
Hi guys
Hate this as I know is a old thread but is really really nice, thanks.
One question tough, I am considering doing the job to and have full kit in my garage.
My belt tensioner ect was replaced 4 years ago aprox 40.000 km / 27000 Miles when bought the car.
Belt looks in real good shape tough, everything else also ok, no weird sounds ect, but time has passed, km/miles has passed I don't want to become victim for hidden cracks lol..
How long they normally last or what is advised replacement ?
My primary concern was to replace the idler pulley, which has been very prone to failure in the M112/113 engines (e.g. CLK, E and SLK class), mainly because it is the smallest pulley in the system (e.g. spins at high RPM) and only has a single bearing.
While with the engine running, I was not hearing any unusual noise, upon removal of the idler pulley, I could clearly hear bearing noise as well see 3 developing stress cracks. Usually the cracks are on the engine side and not visible.
A new pulley is not expensive and I used the INA OEM unit. While many parts suppliers also offer less expensive URO brand replacement parts, from what I've read, they should be avoided.
On a CLK320, it's a very easy DIY (e.g. plenty of room).
I also replaced the belt, which surprisingly at 12.5 years and 83,500 miles appeared to be in very good condition as well as the belt tensioner, which was the factory installed original old design and had bearing noise. My total cost was around $150.
Given that while driving, a failure in the accessory belt system, would be quite inconvenient, dangerous (e.g. loss of power steering, brakes, engine over heating etc.) and much more expensive to repair (e.g. towing to a repair facility), I considered this preventive maintenance to be inexpensive insurance.
Hi guys. I drive a MB CLK320 2004 W209 now 65000 miles. I have been intrigued with a squeaking sound coming from the front engine more likely the serpentine belt or one of its pulleys. I removed the serpentine belt and checked the pulleys. The idler pulley when spinning was noisy. I replaced the serpentine belt and the idler pulley. The squeaking sound diminished a bit but didn't go away. My next step is to replace the belt tensioner. MB original part is expensive. Dealer price is $280, or $180 online. OEM prices varies from $60 to $130. Any OEM brand recommended for the belt tensioner?
I've been ordering quality maintenance/repair parts from AutohausAZ for more than 12 years (air filter, oil filter, idler pulley, serpentine belt, belt tensioner, blower regulator, spark plugs, offset spark plug boot removal wrench, mass air flow assembly, hydraulic fuel pump relay, light bulbs, brake pads, brake fluid, wiper blades etc.). Saved a ton of $ (e.g. free UPS Ground shipping on orders over $75 and no sales tax) and IMHO they source parts from the same manufacturer's that MB does. Note: As long time reader of MB boards, unless your going to sell your car in the near future, I would avoid the less expensive URO branded parts.
Last edited by Serndipity; Aug 14, 2014 at 05:00 PM.
I think that the torque specs on those posts are referring to the E12 bolts that fasten the entire belt-tensioner assembly to the vehicle, and are not referring to the bolt inside the pulley (of the belt-tensioner).
Since I don't know the exact torque spec I just fastened it tight by hand...without using a torque wrench.
I'm still interested in knowing what the torque spec is for that middle bolt that goes inside the pulley (of the belt tensioner).
I think that the torque specs on those posts are referring to the E12 bolts that fasten the entire belt-tensioner assembly to the vehicle, and are not referring to the bolt inside the pulley (of the belt-tensioner).
Since I don't know the exact torque spec I just fastened it tight by hand...without using a torque wrench.
I'm still interested in knowing what the torque spec is for that middle bolt that goes inside the pulley (of the belt tensioner).
I am just in middle of same job and came in to check torque specs. Re the tensioner pulley, I am too just replacing the pulley. MB shops probably just change the whole thing!
For the idler pulley bolt, I set my wrench at 15 ft-lbs. But I did not go that far. It was really tight at less. Without removing fan, access is not too good (I am working on W210) - that may have something to do with it.
Seeing bolts are all same size, I think I will set to 14 ft-lb and if it feels really tight before that, stop then. I will probably put blue loctite on. Problem with that, is that you actually end up with high tension in bolt than when dry. So maybe back off even a little more?
I'm glad you replied to keep this post alive. Sorry for not responding sooner, since I thought this post was dusty...
Regarding loctite...I personally have tightened a couple of belt tensioner bolts at the same measurement even with loctite on it. So I wasn't worried about the loctite changing the specs...your call though...
HealthBar....from what you wrote in the thread you provided, which I have included below, one of your pulleys may have a bad bearing.
I had the same symptoms you described and didn't even have to check any of the pulley bearings by relieving the belt tension and manually spinning each pulley, because when I opened the hood, it was obvious that the rattle was coming from the water pump pulley and the belt was also moving fore and aft as the pulley spun.
Also noticed that in post 18, you replaced the pulley on your belt tensioner with a Uro part, which have a history of not working properly and/or soon failing after being installed.
Only use genuine MB (OE) replacement parts, or from the company (OEM) that manufactured the part for MB, never knockoff parts.
<><><><>Included text from referenced thread<><><><><>
RE: MBZ 2001, C240, W203, M112, 6cyl., 115k miles
My belt tensioner is doing the shimmy without the music....
My belt tensioner is rattling & shaking in the Drive and Reverse positions, Only when I press on the brakes and the car in a still position (not moving). The belt tensioner does not rattle when I drive or when the car is in the Neutral or Park positions.
I recently tightened and replaced new bolts to keep the belt tensioner fastened (to the engine) according to the proper torque specs, yet this rattling noise is still happening...
The pulley itself is not making any off noises, but the tensioner itself is shaking even though both tensioner-bolts are tight. Rodney from another post told me that the inner spring within the belt tensioner is failing and that a new belt tensioner needs replacement: https://mbworld.org/forums/c-class-w...g-shaking.html
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