Jasonoff

Wonder if merc had a batch of garbage bearings?

I have 78k miles on mine and as you can see from the belt pics it looks decent. All the idler pulleys spin freely without any noise and the tensioner felt strong.

Alex.currie44

While it was a long time ago belts like women in a bar can be deceiving!
I am not sure I know what year your car is but if it is a 2009 or so I would not be trusting appearances. The belt is cheap insurance.

AMG3.2

I was roughly at 51k miles. At least they give warning though, mine was making a lot of noise.

Celicasaur

My belt sheared last might 100 miles away from home. I wasn't impressed.

Car was towed to MB today for diagnosis on Monday. I'm hoping it's just an idler pulley and replacement belt. I noticed some light puddles of fluid under the car whenever we moved it in stages onto the tow truck

Car has 91k miles on it.

Infiniti

sorry to hear bro, hope its simple

Amr_c63

just hope it didn't get sucked behind the crank pulley and into your engine , maybe that's why you saw the oil ! Keep us updated as this is something that everyone should always keep an eye on (preventative maintenance)

Celicasaur

Thanks mayn...

That would really hurt...

For what it's worth, when i had a look under the hood, the belt was still somewhat in one piece and fitted around the pullies...it was just ripped up and looking like a cat had gotten really pissed with it. I'm hoping it's just an idler pulley that seized, but life might not be that kind. Annoyingly i was having such a nice drive as well and the car was feeling so strong. I guess i'll know more in a couple of days.

Savage-wp

Sorry to hear Celicasaur.
I hope it is just something simple like a seized pulley and broken belt.

Mort

^ +1 one this. I have heard of lots of other damage being possible but it sounds like you might be OK if the belt was not wiping around in there too much and chewing up electrical wiring. Fingers crossed for you.

Another reminder to check the drive belt and pulleys on a regular basis. I have it on my list to change them with billet pulleys and this winter layoff it will be.

BLKROKT

Sorry to hear man, and just when you had the car performing well. That belt whipping around could have easily cut a coolant or oil hose. Highly doubt any fluid loss would be from anything other than that. Hope it’s an easy fix.

Celicasaur

Been AWOL lately and busy with work etc but at least I've somewhat fixed the car now.

So MB had a look and said that the belt had caused a light chip to the outer edge/lip of the AC pulley and they would need to replace the entire unit, as they don't sell the pulley for it....this, along with just the two failed pulleys was billed to me at £2,400GBP ($3,200USD). Needless to say I asked for the car back and paid them for their one hour of diagnosis (which probably took all of 5 minutes anyway.

So, with the car home, and on the driveway for my own inspection, I was greeted with a belt that looked rather sorry for itself (notice the really low coolant reservoir though) :





The top left idler pulley is the one that totally seized, but it also resulted in the pulley next to it getting all hot under the collar and taking it's top off, although it hadn't actually seized.





Comparing the old pulley to the replacement



You can see here, the plastic melted which caused it to come off the inside metal area




I was going to buy the billet pulleys that Shardul sells, but sadly stock availability at the time and international postage/customs etc would have meant 2-3 weeks of down-time which I didn't want, because I was having lots of fun with my HP tuners thing in my spare time. So I went to my local MB parts dept and the guy had them all in stock - awesome. Seeing as ALL of my pulleys needed replacing, I decided to do the whole lot (unlike the dealer whom only wanted to replace the two failed items). MB don't sell the tensioner pulley on it's own, but you can get a Gates pulley from eBay, which I did and it will probably arrive with me tomorrow I think.

For those of you wondering how/why I said they all needed replacing - remove your serpentine belt and try to spin the idler pulleys with your fingers. If they spin freely and/or make any form of sound, the road to failure has begun and you should replace them. Mine were all pretty bad and loud. I wonder if my alternator will charge my battery a little better now...it used to only manage little over 12V while the engine was running...maybe there was belt slippage going on.

Anyway, worth noting that one of the pulleys has been updated - refer to the part number and match the location with the diagram:





I'll wait till the tensioner pulley is fitted before taking the car for a drive. However I'm a bit concerned as to where the coolant has gone all of a sudden because I can't see any leaks on the ground after starting the engine and allowing it to idle for a bit. Hopefully there's a split hose somewhere that I haven't seen yet.

Oh and I almost forgot...the DIY repair cost just ~£190GBP. Crazy difference, huh?

Infiniti

glad you got it figured it out man. i think one of my pulleys is making a noise. I'm going to check now. sucks about the coolant man.

LOOK AT THAT E39!

Celicasaur

Well-spotted my man. In my opinion it's the best V8 super saloon ever made.

Jasonoff

I'm curious if it was actually the plastic that failed which ended up wrecking the bearing in the process?

I checked mine when I did my belt a few months back. They all spin without grinding but I'm going to swap them all out anyway. I'm up over 130K km now.

Edit: Fixed the stupid...

Celicasaur

yeah no, i actually meant that tbh....maybe it wasn't clear from what i wrote though

if you flick/spin the pulleys with your finger and they spin freely with inertia (they keep going for a second after you've flicked your finger off) then they are definitely toast.

however yes, a healthy pulley will spin freely and silently, but it won't continue to spin after you take your finger off it.

BLKROKT

No, he was correct. They should NOT spin freely when new, torqued correctly in place. They should be fairly tight. Mine don’t spin unless I give them a good push.

If yours spin easily by finger, they’re cooked.

Jasonoff

Yeah my bad, context error on my part. Spinning with no resistance means all the grease is gone.

Edit: here's a good vid. The one that spins like a Rollerblade wheel is the bad one.

Celicasaur

Strange as it seems (and I'm sure I might get some flack for this) but I've been monitoring my battery charging with the engine running and I'm happy to report that it's now a stable 14.5-14.6V

I know it doesn't make sense, as the alternator pulley is still fine, but I don't know what else to say about it really. I wonder if anybody else with a failed set of pulleys might notice this....of course I realise that not everybody looks at their battery voltage often too.

Jasonoff

Old belt could have been slipping.

Infiniti

hmmm highest i see is 14.1

Jasonoff

Guess I should have actually checked ALL my idler pulleys lol. The tensioner pulley is like new, the two under the PS reservoir are not bad (not amazing but still have lots of life), and the smaller grooved one by the timing case is ok.

But... the one beside the AC compressor pulley is toast.

cbird805

Did you ever figure out why the coolant was so low? Mine did the exact same thing. I just happened to be taking it to my mechanic when it got a coolant low message at start up. I checked the overflow tank and it was below the low line. I drove 18 miles without issue, then the battery warning message popped up and lost power steering. I limped it about a 1/4 mile to the shop. My mechanic told me belt was toast, idler pulley melted, took out the water pump as well. I told him to give it a good once over after repair, and he said that should be about all that it needs. I didn't think anything of the coolant low indication, until you mentioned it. Perhaps, it is a early sign of belt/pulley failure that we should be aware of. Had i known to check the serpentine belt after a coolant low warning, I may have prevented the water pump from being replaced. Hopefully, that is the extent of damage caused by me limping it to the shop.