IntoTheBlue

So I have a fun little noise coming from the front passenger side of my engine bay (m271), diagnosed as a bad alternator pulley from the dealership, (makes a noise when the A/C or air is on, especially in reverse after startup, doesn't affect the cooling or anything else though).

The dealership wanted to charge $700 for the pulley and labor which is just crazy as I remember replacing some serpentine pulley myself on my Jeep for $19 back in the day.

I won't be doing any work on the Benz myself though, but wondering the best/cheapest way to get this replaced.

Does anyone have a part number or description of the pulley as searching online gives me 2 results, a 6 groove or 7 groove pulley.

If having a place like Pep Boys do the labor, would it be easier to just buy a new alternator with pulley attached and have them replace that? But again when looking at Bosch alternators I'm seeing either a 6 or 7 groove, 120 or 150amp, can anyone point me in the right direction?

Thanks

infected

The alt itself was around $500 for a remanufac Bosch back when I did mine in about '10. I don't think the price should have changed much since then, the belt is cheap. Check if you can give them your core for a credit back.

torake

The belt and pulley should be no more than cirka $100 together, and on the M271 you can replace them easily in a half hour. If you want to DIY, you need a special alternator freewheel tool, cirka $30

Measure the pulley with a caliper, it should be something like 46mm wide, 60mm outer diameter and count the grooves. That way you will get the correct part. OEM might be INA 535001610

Boom vang

seems very expensive, not sure if it is a half hour to re&re it, took me about 45min for each (1.5hr) all said and done as many parts have to be removed in a M271 to get at the alt such as wide band silencer, under tray and just tight working conditions. It is not hard just awkward.

The fact that it makes noise only when the A/C is on leads me to believe it is not the pulley. The pulley should not make noise unless it is misalligned, usually it is the bearings that make the noise when they are worn out. Are you sure it is not the belt or compressor?

For $700 I would hope that they are replacing more than just the pulley and would expect the whole Alt and still have some change in my pocket for a rebuild. Make sure you are replacing like for like and not to substitute for a different brand Valeo / Bosch which can give you issues.

I would suggest you go to an Auto-electric place to get it done than the dealer as the dealer will only replace and if they do sell a rebuild they would be getting from an auto-electric shop and marking it up

torake

Removing everything that is in the way including the belt takes 6 minutes if you've done it before.

Then it's just a matter of using the freewheel tool to loosen the pulley. I did the pulley replacement in 30 minutes and I am not a pro.

VVF

FYI, I bought a remanufactured alt from rockauto for around $140 a couple of months ago.
Don't remember how many grooves... 120amp (150 is for c320 I believe)

Check whether you have Valeo or Bosch before ordering.
This is reman Bosch:
http://www.rockauto.com/catalog/more...456&cc=1431038
$125 + $80 core (you pay 205, then ship your old alt to them, they credit your $80 back)

And yes, it is the pulley. It's supposed to freewheel in one direction, but it seizes and when the AC compressor loads the engine the belt speed decreases, but the alternator has high inertia and tries to spin the belt faster, resulting in slipping and rattling etc. I had the same problem as you. Replaced the alt - problem gone. If you don't replace it in a timely manner, you will kill your AC compressor which is "a little more expensive"

slammer111

Trying to replace the pulley on my car. Can anyone who has done this job please chime in?

On the M271 the pulley is easily accessible by simply removing the inlet pipe and one of the silencer hoses (takes 2 minutes in total). However the pulley is seized onto the alternator like a ****. Even doubling up my 17mm wrench and using a breaker bar on the shaft isn't working.

I have the 33-tooth spline + long T50 bit. Based on the replacement pulley I believe the spline bit has to be turned counter-clockwise to loosen off the alternator. Is this correct?

Also, how much torque can this thing handle? My biggest fear is stripping that T50 alternator shaft. If that thing goes, I'm toast.

Thanks in advance.

ODB

Did this exercise last year. At first, tried to replace it without removing alternator - no luck at all. I tried this multiple times

Than I decided to remove alternator and after about an hour I was able to unscrew the pulley using impact wrench and putting alternator in vise.

It was really hard, man. Good luck!

VVF

https://mbworld.org/forums/c-class-w...ditioning.html

slammer111

VVF, thanks for posting the link, and thanks to Scottonfire. Results posted in the thread in that link above.