That part that you need to replace is called the "air pump". Its not cheap, you can take it out easily and add positive and negative to move the motor to test it. It basically pumps air into your engine when needed. Its very easy to replace, probably ten minutes. Practically all Mercedes-Benz have this air pump in front of the engine.

 

what you've identified is the air pump for the secondary air injection. It will make a little noise, but it shouldn't really rattle.

 

pump is only about $160 though at parts.com

 

Do they sell the tensioner pulley separate? All im seeing is the assembly.

 

Yes, tensioner pulley sold separate. It is cheep. Here in Uk i paid around £20.

 

Good call changing it, mine started making noise and before I could replace it, it broke off the bolt. Took me 4 hours to remove all the radiators and header to drill it out and put a new bolt in. My pulley was $390 (list is like 450 I think).


Sent from my Autoguide iPhone app

 

on the w220, can you remove the idler pulley without having to remove the radiator fan????

 

I can say, yes. You dont need to remove radiator fan, but if you have bigger engine you MAY have to, because of limited space.
Go along with diy, its easy. If you need more info ask.
Regards,
Saulius

 

For which engine? The S600 idler was normally threaded...but required removal of the upper hose, draining of the radiator, and removal of the fan to get to it...

 

2000 s430 engine........

 

replaced my idler pulley today. it was LITERALLY being held together by the tension on the belt. it came off in TWO pieces, split right down the middle. the bottom piece is NOT a gasket, its part of the pulley...........

 

Pulley



Is that pulley replaceable with a later version that won't split?

 

Wow I just went through this exact failure on my 2006 Sprinter van. The thing has been a pleasure to own and drive since new, and I'd changed the tensioner but not the idlers at 100k. On a long trip up north going 70mph on the highway one of the idlers split in 2, cut the belt in 2 so half was still working but half was shredded. The shredded part acted like a mace in the engine compartment and wrapped around everything, also severed the transmission cooling line to the radiator.

What a nightmare, towed off the highway, needed new viscous fan, belt, idlers, transmission fluid, and lots of cleaning up. Because of all the belt debries flying around my AC compressor died in 2 months and my PS pump died in 3 months after the pulley failure.

The whole front belt drive of my motor is new now, at about a $3k cost. 2 of these incidents happened on long trips and I had to go to an MB dealer once and then an independent MB shop the other time, and one I did myself.

I would say that changing those pulleys is good cheap preventive maintenance at about 100k!

I'll do it on my S Class when I near that mileage.
Todd

 

So sad to hear about your bad pulley.
I would suggest to check pulleys now and again because my other W220L has covered only 67849 miles and idler is so wobbly. Easy and cheap change.

 

Bad pulleys



Has MB not corrected the problem by making a different pulley that doesn't split?

 

I dont know, maybe mb has updated version of pulley. Even if not, just check regulary.

 

Should the tensioner, idler pulley and the belt be replaced or is it only the idler pulley that fails ?

 

My policy is to check the condition of the tensioner pulley and idler pulley anytime that the belt is off for any reason. If they turn smoothly and easily, with just slight lubrication resistance, and show no damage or wear of any kind, I leave them alone.

You might be surprised at how available these items are. My local auto parts stores (Advance, Autozone, O'Rielly, NAPA) all stock them to some extent for the W220 S430. A Dayco idler was about $13...

 

That is cheap, $13. I have always been going in the OEM parts direction.


I see the local O'Reilley has the Gates idler for $39 and a Gates Tensioner for about $124. belt is $37, for a total of $200 for all there, plus Taxes.
Anyway, not bad and its good to know that local shops carry parts for the see European cars.

 

My apologies - I mixed the prices at Advance. They have the idler for $15 to $39, but the Dayco is $38.

Advance Auto Parts: Search Results for belt idler pulley

Their prices on the tensioner are equivalent to those you found. Of course, if you order on-line and pick up thirty minutes later at the store, you can save 15% - 20% most of the time.

It is interesting that they sell one brand (Litens) that has a limited lifetime warranty.

 

Hello I have a 2000 s500 my serpentine belt broke at 160k I've owned for about a year so dont know what has been done maintenance wise beside changing fluids and brakes. I'm trying diy .I've found the idler pulley sounds like a rollerblade and the tensioner pulley is hard I couldn't spin at all. I assume this isn't normal but I haven't seen anything yet to confirm .can anyone please help ..thanks

 

Both pulleys should turn smoothly and quietly.

 

Ok thanks Wallyp.! I'm still waiting on parts they're 2days out .my cars been sitting about a week and a half. I just noticed tonight when pulling in the drive theres a puddle of oil under the car. Nothing visible upon opening hood, is the something else the seized tensioner or the belt could've broke ??

 

Possible, but not too likely. It can be (usually is) very difficult to find the source of a fluid leak with the lower engine covers installed. Don't forget the possibility that the leak could be power steering fluid or transmission fluid, or even coolant.