Thanks so much for sharing, that's very helpful and clear

As I said, I am at ~78k miles, how much is the life of idler pulley and tensioner? Is it a maintenance item to replace them both? Again, I am not having any abnormal noises or squeaking or anything.

Thanks again

 

I'd say these are maintenance items since they will wear out, but there's no specific time frame. Just keep an ear out for noises, and inspect the belt at every A/B service interval.

 

I used this you tube video for guidance: Looks real easy to change your serpentine belt. I used an ice pick.

 

Thanks for sharing, very helpful.

So if I understand it correctly, for just replacing the belt, use 17mm socket and rotate tensioner ccw and remove the belt, no need to use any Allen key or anything, correct?

 

You need the allen key (Or Something Like It) in place to put the new belt back on. This way you can use 2 hands. I took a picture of mine before removing to ensure correct replacement. I didn't want to trust my memory. Don't forget to remove the allen key rotating the tensioner ccw when you are finished with the replacement. This puts the tension back on the new belt.

 

I see your point, allen key is going to hold the tensioer in place, so that I can easily place the belt on and then remove it, to stretch the belt.

Makes perfect sense. Thanks guys

 

You can use an Allen wrench or even a screwdriver - anything that fits in the hole to hold the tensioner in position.

 

Ah I didn't know about the Allen hole to lock it in release, I just put the belt on everything else, then levered the tensioner and slipped it over it, not too difficult to do.

Shall do this when I change my tensioner tomorrow.

 

May I ask why you are changing the tensioner? My CLK320 has 102,000 miles and I didn't change mine. I didn't see any need to. Is your making noise?

 

Are you still on OE belt or replaced it?

 

I replaced my original (OEM) with a Continental Elite belt. Continental merged with Goodyear recently. I got mine on Ebay for less than $13 Rock Auto has the same one for $26 Rock Auto has some really good prices though. They are very competitive. They sell a "Belt Drive Component Kit" which includes the belt, tensioner and idler pulley by Continental for $139.79 for my CLK320. I only changed the belt. I always shop around. I generally go to Parts.com for OEM only parts, AutohausAZ, Oscaro, Bosch, Rock Auto, Bilstein.

 

Yeah, I bought elite one from Amazon for $10.xx. Rock auto service has degraded in the last few months(years) and they aren't as competitive as they used to be. I thought about 'Belt kit' but it'll be an overkill at this point.

I just ordered the belt, more like good to have it.

 

So I changed both idlers on my engine, there was no noise, but when I had the belt off, and span the blocks, I could feel the bearings where on their way out.

Once they were replaced, I looked at the tensioner and it was wobbling a little, which I thought was a tad strange, so I took the belt off and span the block on the tensioner and the bearings on that we're also soon on their way out.

But you have to change the whole tensioner unit.

And now, the tensioner is still/is not vibrating up and down in operation, so I can only assume the tensioner was past its best too.

They probably had a little life left in them, but I like to keep on top of everything.


MOT on Saturday, but I suspect that it will pass with flying colours.

 

Dang, wrote too soon. The warm weather is just coming to the North East so I haven't been under the hood yet for anything serious

I get off a plane in St. Louis & wife calls from NJ. She had to call AAA to have the car towed. She had no power, battery light came on she drove it another 1/2 mile anyway. Lovely. Looks like the timing belt is shredded.

 

*auxillary belt. Timing is done via chains on our Mercs. Timing truly would have been a disaster. Don't know how the car would have taken to being driven without the water pump turning though.

 

I know I'm late to this thread but I had the same problem not too long ago. Started the car and I heard pully noise. Thinking it was just a pulley to be replaced I drove home. Much to my surprise when I opened the hood the tensioner pulley is halfway off the shaft, with the dust cover and bolt missing. You can buy the pulley alone, but not with dust cover and bolt, so I had to replace the whole assembly. $135 from local auto part store, took about 20 minutes.
Going in I was very nervous about the serpentine belt, but it was so easy. Lots of youtube videos helped.