Alternator belt - PeachParts Mercedes-Benz Forum

sokoloff · #1 02-09-2023, 02:47 PM

This is for my '99 E300D with 226K miles.

Driving along with no issues when all of a sudden the battery charge warning light comes on. See photo. That's unusual because I rarely drive the car and while it sits in the garage, I always have it on a trickle charger. This morning the charger showed that it was fully charged.

Then the car is running just a little hotter than usual. Then it starts getting hotter and hotter and eventually hits the red line. I immediately turned the heater on and up to max and the temp came down to near normal. It was at this time that I figured I better pull off the road and see what's going on. As I was pulling off, I lost my power steering.

Called AAA and got the car towed home. It now sits in my driveway. Upon looking at things, I see a lot of slack in the belt and it is not on the alternator at all. See attached photos. The belt issue seems to be the explanation of everything.

As an FYI, the belt looks good, but hasn't been replaced since 2013, i.e. 60K miles ago. I replaced the spring for the belt tensioner 15 years ago and over 100K miles ago. I did all of that work myself, but at my age have probably forgotten more than I can remember. I'm guessing/hoping that there is a DIY video in the maintenance section, but any help or tips you guys have are appreciated.

Thanks.

pimpernell · #2 02-09-2023, 03:38 PM

I think that you got your moneys worth out of the parts you put in yourself, and I would take it into a reputable dealer to have the necessary repairs made. Good luck

Graham · #3 02-09-2023, 04:37 PM

H Len,
Funnily enough, I had the same thing happened once when we were in Myrtle Beach in our 98 W210 E320. We were on the elevated part of Hwy 22, heading towards the exit near Tanger Mall. First sign was charge light, then power steering and brakes sluggish, car began overheating. Nowhere to pull off on that part of the hwy. I opened all the windows and turned the heater on full. This actually stopped the rapid rise in temperature.

Once down the ramp onto Kings Road, we limped back to our condo in Kingston Plantation. I had no tools and didn't yet know what was involved, so called AAA in morning. They towed the car to the dealer who was in Conway, back then. We went with them. Young lady mechanic had the new serpentine belt installed in next to no time. We then drove to Diamond Back course (near Loris) and made our 1pm tee-time!

The routing on your E300D is probably slightly different, but it is quite easy to install a new belt on my E320. You might want to check teh tensioner and the idler pulley (if there is one) because I have also had those fail. There is likely a tensioner that needs to be pulled back to allow the belt to go on. Routing is the key. I found this on BW W210- forum. If you have the 606 engine it may help? You should see a bolt head that you can put a socket on and then rotate the tensioner against the spring to allow belt to slip on. I am sure there is a better write up either on BW or somewhere on net on how to do this. Also of course in WIS. (sorry, I don't know why the image grew in size!
https://youtu.be/A7bER9cmqwM

Graham · #4 02-09-2023, 04:46 PM

Len - Look what I found on Benzworld W210 forum

https://www.benzworld.org/threads/e300d-replacing-serpentine-belt.1702053/#post-5692090

sokoloff · #5 02-09-2023, 06:27 PM

Thanks Graham, but I'm not sure that Len guy knows what he is talking about.

Hoping for an easy fix with no collateral damage.

engatwork · #6 02-09-2023, 06:51 PM

You need to replace the alternator pulley before putting a new belt on it.

Also check that the tensioner pulley and the idler pulleys do not feel "loose" when you spin them. If they spin freely replace them too.

sokoloff · #7 02-09-2023, 07:29 PM

Thanks Jim. Yeah, my plan was to investigate the cause and not just replace the belt, especially since the belt looks so good. Something must have given way. Not sure if this is a connection, but over the last few times I drove the car, it seemed like there was a little more under the hood noise than usual, but since I drive the car so infrequently, I just thought maybe I was imagining that. But that extra noise certainly could have been a pulley or tensioner on the way out.

Graham · #8 02-09-2023, 08:39 PM

Len, thinking back to belt issues I have had on my E320:

- the first issue was just the belt. Dealer checked other items
- second issue was noise - that was from the idler pulley bearing (replaced idler) Seems your 300D does not have an idler - see video above that replaced the drawings.)
- third was noise again. This time the tensioner bearings (replaced tensioner)
- fourth time noise was from the alternator bearing. I pulled alternator, had it checked and the shop said not to worry. But I put in a reman alternator anyway - R&R not easy job on V-6! Once was enough

For 2nd.3rd and 4th issues, the belt was still good.

Later, the A/C clutch pulley started making a lot of noise. A/C was not working anyway, so I removed the pulley and put in a shorter belt that bypasses the A/C compressor.

Not sure what Jim saw on your alternator pulley? They look indestructible. But they can perhaps be misaligned either due to bad alternator bearings or mount?

Anyway, I am sure you will sort it out!

BTW - The used ABS unit you once bought for me is still working fine. We have stayed in Canada for past 3 winters and it has kicked in a number of times on slippery roads!

engatwork · #9 02-09-2023, 09:32 PM

From what i can tell by picture you need a new alternator pulley or you have a fastener issue. They are not just a pulley. I don't remember name but it is a design for smoother operation.

Graham · #10 02-10-2023, 12:42 AM

It does look like the pulley is quite far away from the alternator. Maybe the nut came loose? Some drawings in this post:
https://www.benzworld.org/threads/alternator-pulley-gone-bad.2517361/post-13411513

EDIT: No nut on this model, it seems. It has has an overrunning clutch with integral locking device. Must have come undone. (see below)

sokoloff · #11 02-10-2023, 10:14 AM

So this morning I wasn't ready to start working on the car, but I figured I'd take a quick look to see if I could see anything obvious. Didn't take long. As soon as I reached down to touch the alternator pulley, it just fell off. I have no idea how it was still on the alternator. See attached photos. So my question is should I give it a try to just replace that pulley and the belt while I'm in the area? Never done this job before. I think I had seen reference to a tool or tool kit for R&R'ing that pulley. I'd appreciate any input regarding that.
Thanks.

Graham · #12 02-10-2023, 11:59 AM

I don't think the pulley on my 98 is like that. Seems it is a an overrunning pulley? Just drives in one direction. Allows overrun from alternator when engine rpms drop? I can't help with that but interested in learning more! Seems it does need special tools.
https://www.pelicanparts.com/catalog/SuperCat/2765/MBZ_2765_ELCHRG_pg1_alternator-pulleys.htm
One option might be to take complete alternator to auto-electric shop and not have to buy special tools? Probably need alternator out anyway for DIY job?

This video explains how to replace a pulley and the tools needed. Not sure if W210 is exactly the same. Probably more over on BW210 forum?
https://www.youtube.com/watch?v=uKwEB9d845M

The INA pulley is apparently equivalent to OE and pretty inexpensive.

dieselbenz1 · #13 02-10-2023, 01:06 PM

Sure looks like an overrun pully. It has likely failed and needs a new one. I had borrowed tools from an auto shop prevously on another vechile.

BillGrissom · #14 02-15-2023, 05:48 PM

I don't know your E300, but that pulley looks like the "AOD" type on my 2002 Chrysler T&C alternator. They have a built-in damper with a spring, which I think allows some slip. They are used on longer serpentine belts to control oscillations, perhaps at certain resonant frequencies. I was getting a strange noise which I thought might be the alternator bearings, but searched online and found the AOD fails on many cars. In mine, the thick spring had cracked apart. A new AOD pulley was only $35 and has lasted ~10 years now. I was worried because I read past stories of that pulley costing ~$150, perhaps when only available at dealers. Check Pelican and rock to check your options. Yours is similar vintage to mine, around when those pulleys began. Don't know if they are still used.

treetops · #15 02-15-2023, 10:17 PM

The video Graham posted is spot on. You will need the splined(sp?) tool and hex head and yep the alt needs to come out. Most fiddely will be getting the alt out, good luck.