Hello,

2000 C280.

Anyone have the torque value for the idler pulley bolt? For the M104 engine it is 30Nm. Is this about right?

Thanks.

25Nm on M112.

Thank you!

My friend saves up copies of The Star for me and I was just getting thru them all. I tear out what seems handy and toss the rest. The Jan-Feb 2011 issue had a short "Three Easy Maintenance Tips-Avoiding the big repair bills" article by Benz Master Tech Ken Adams.

One of them was the idler pulleys on 1998-2000 V6 and V8, M112 and M113 engines. Apparently these develop cracks and if not caught in time will disintegrate, throw the belt and all sorts of hell will ensue.

I have two M112s that I care for, a 1999 and a 2000 C280.

Gently pry off the cap (much easier to remove and replace vs M104, thank you MBZ for this small thing). Take a mirror and flashlight and check the front and as much of the back of the pulley as you can. You are looking for cracks and if you see one you probably have more.

The pulley on the 1999 C280, 85515 miles may have been replaced at 42m. The service record indicates "front crank pulley came apart, replaced front timing cover,upper oil pan,belt,tensioner,crank pulley dampner, all goodwill". Not sure if they are referring to this pulley or the infamous harmonic balancer. No cracks in the front but I do see one on the back.

Use 17mm socket (12 pt better) on the belt tensioner, CCW and release the belt from the pulley. Approach from about 10 o'clock because your breaker will run into other things when the springs unwinds to the right. T50 torx on the bolt. No problem removing this bolt. In some applications the radiator/shroud needs to be eased to get this long bolt out. Pop in new pulley and torque to 25Nm or 18.5 ftlbs.

The 2000 C280 is the same except you use an E10 socket to release the belt.

Both pulleys were dry but not making much noise yet. You could hear the bearings click if you shook them.

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