Serpentine belt - good or bad? - PeachParts Mercedes-Benz Forum

VW1300 · #1 06-17-2012, 06:24 PM

Thanks to all who replied in previous posts about my E300D questions. Attached are two pictures - first you can see the grooved side of the belt - there are some cracks etc but the backside looks evenly worn. Second picture shows a little bit of the tensioner mechanism.

Prepurchase inspection mechanic said belt and tensioner are suspect - do you guys agree? I've never dealt with this kind of belt before so I have no experience to go on here. There doesn't seem to be undue noise coming from the tensioner when the engine is on as far as I can tell.

thanks,

engatwork · #2 06-17-2012, 06:55 PM

When cracks appear it is time to replace the belt. If over about 150k miles on it replace the tensioner pulley too.

qwerty · #3 06-17-2012, 07:15 PM

Quote:

Originally Posted by VW1300

I've never dealt with this kind of belt before so I have no experience to go on here.

There is an app for that.

Gates Parts Image Capture (PIC) Gauge

And a free belt gauge as well.

VW1300 · #4 06-17-2012, 07:36 PM

Quote:

Originally Posted by engatwork

When cracks appear it is time to replace the belt. If over about 150k miles on it replace the tensioner pulley too.

Just the pulley, or other parts as well?

thanks,

Jeremy5848 · #5 06-17-2012, 07:59 PM

The problem is not the pulley but its bearing. The tensioner assembly seems to have a lifetime of about 100,000 miles, give or take. As the bearings wear (the arm has one too, although it's just a sleeve, not a ball bearing) the arm is pulled out of alignment by the belt and the wear increases.

Your belt should be replaced but if it is not worn on the edges (usually one edge more than the other) then the tensioner may be OK. You might ask the mechanic why he thinks the tensioner is suspect; the answer would be informative, both about the tensioner and about the mechanic.

Jeremy

vstech · #6 06-17-2012, 10:16 PM

it appears to be the original tensioner. I would want the belt off the car, and spin the tensioner pulley, and feel for play/wear in the bearing of both the pulley and the tensioner arm.

VW1300 · #7 06-17-2012, 11:00 PM

OK. I'm guessing the arm should not have any play? Or just a tiny bit? At approaching 200K miles, I wouldn't be surprised if the arm has play - it looks like it's been there as long as the piece it's attached to - that sort of whitish aged look. Replacing the arm + shock adds $100 to this procedure but I'll do it if it needs it.

I have been reading past posts on tensioner arm etc replacement - it looks like one key thing is to remove the spring so the arm has more freedom to move. Also to have a coat hanger handy to help thread the belt over bottom pulleys.

thanks,

connerm · #8 06-18-2012, 09:09 AM

Check out this thread with some pics. All of the tensioner parts should be inspected not just the pulley, shock, spring, and belt.

belt tension arm collapse

Mark DiSilvestro · #9 06-18-2012, 10:59 AM

Not certain it applies here, but I saw a tensioner fail on a friend's '84 2.2 190D. Suspect the shock went and the resulting vibration caused the tensioner to break it's mounting area from the timing-cover.
Noticed the replacement timing-cover was a redesigned casting, with thicker ribs around the temsioner mount.

Happy Motoring, Mark

vstech · #10 06-18-2012, 12:51 PM

be CERTAIN when you take out the tensioner to replace it, that the TC cover is CLEAN, and you get the arm mounted without any grime under it. clean out the thread area on the cover. then be CERTAIN you get the bolt threaded in by hand prior to putting any tools on it. I also think some BLUE loctite is a good idea.

as for checking it, the bearings should both be SMOOTH ZERO play in any direction. if you THINK you feel something, just replace it! I'd also replace the shock, and the spring as well. I stupidly replaced everything except the shock and spring, and the stinking thing broke about 100 miles after the repair. new shock and spring, and no problems in 100K!

vstech · #11 06-18-2012, 12:54 PM

oh, you might want to pull the vacuum pump, and inspect the bearings on it as well. a new pump is about $400 but it's far less than the engine! an updated gasket will set you back about 7.00, so the peace of mind knowing the plastic cages on the bearing are not gone. if they are gone, but ALL 12 BALLS are still there, change the pump! if ANY balls are gone, you need to find the missing balls in your oil pan, and change the pump.

Jeremy5848 · #12 06-18-2012, 01:57 PM

The '97 E300D will have the updated vacuum pump with an improved bearing but it's still worth pulling for an inspection as long as you're working in that area. Even the new bearing can fail and dump pieces into the timing chain case, as vstech has written. This is a failure you do not want to wait for.

Mark's friend's problem (in which a failed tensioner took out the timing case) is also worth remembering. It's a lot more work and money to replace the timing cover than it is to replace the entire tensioner assembly.

EDIT: Also see this thread.

Jeremy

Mark DiSilvestro · #13 06-18-2012, 07:50 PM

Quote:

Originally Posted by Jeremy5848

The '97 E300D will have the updated vacuum pump with an improved bearing but it's still worth pulling for an inspection as long as you're working in that area. Even the new bearing can fail and dump pieces into the timing chain case, as vstech has written. This is a failure you do not want to wait for.

Mark's friend's problem (in which a failed tensioner took out the timing case) is also worth remembering. It's a lot more work and money to replace the timing cover than it is to replace the entire tensioner assembly.

EDIT: Also see this thread.

Jeremy

My friend got the car at auction with 400k on the odometer, and the failed vacuum pump in the trunk. After he installed a used pump, I told him that he needed to find out where the missing balls went, but he didn't want to spend the money. Three months later I got to install a new timing cover, and fish the balls out of the oil-pan anyway. Don't know how much longer it would've lasted as then the 5-speed tranny started growling, so he sold the car.

Happy Motoring, Mark

VW1300 · #14 06-18-2012, 11:17 PM

Hmmm. I know I should pull off the vac pump while I'm there but frankly I think I have my hands full with re-doing the belt and tensioner. I say that because I'm not a very experienced mechanic and I try to take new things in bite-size chunks. I'll keep an ear out for sounds from the vac pump though.

It sounds like taking the serpentine belt on/off is really not so hard once you know how, so when more pressing issues are dealt with, I can come back to the pump.

Thanks,

vstech · #15 06-19-2012, 07:22 AM

the belt is very simple to remove. only a 13mm wrench and a 10mm lever (like the tire iron handle) is needed. and once the belt is off, the vacuum pump is pretty simple to remove also. just a few 10mm bolts to loosen. while the tensioner is out. the issue is, that without removing the tensioner, the vp bolts are hidden.
so, after you have the tensioner off, please take the time to remove the vp bolts, and inspect the bearing cage.