Belts and overheating at idle. - PeachParts Mercedes-Benz Forum

networkboy · #1 02-10-2007, 02:54 AM

Ok, so I knew the belts were in "not so hot" shape but I've been putting it off. Couple days ago I started noticing a mild burning rubber smell from the car when I gout out and was walking in front of it. By the time I popped the hood it had dissipated. Yesterday I noticed when at idle the temp rose rather quickly to about 100C, at which point I shut it down (I was sitting in the driveway waiting for the wife ~10 min. In summer at 105deg out the car barely got to 85 under regular driving conditions + stop and go). The moment I started driving the temp came right down.

Upon a closer inspection with a cool engine I find the following:

The Alternator/water pump belts are under less tension than the other two belts (using my roughly calibrated finger).
One of the two belts appears to be stretched compared to the other (facing the car the belt closest to the engine "bows" outward a bit more than the other belt.)
The stretched belt has a band (about the first third, closest to the engine) that is glossier than the rest of the belts (melting?).

So a handful of questions:

Is it a reasonable assumption that the belts are slipping, thus the poor performance of the pater pump at idle, and the friction of slipping causing the melting?
I have the FSM, but are there any Gotcha's to changing the belts (have those too).
Is this one of those lean over the top of the car and a couple awkward reaches and you're done, or is this a jack it up and get under the car to do it right kinda things? (I'm in an apt that won't allow anything but "minor fixes", to them minor means anything that you can do sitting in the car or leaning over the hood, the moment you're even looking under the car with a flashlight they're on you).
Any special tools?
Belt tensioning. Help here, I don't have the tool in the FSM, any "rule of thumbs" for getting it right? (Both my other vehicles are serpentine with tensioners, so my experience here is nil )

Thanks everyone,
-nB

300SDog · #2 02-10-2007, 03:09 AM

Maybe just tighten the belts you've got.

networkboy · #3 02-10-2007, 03:13 AM

I was thinking about doing that to get me by the rain...
They are pretty ratty though. (and I think mis-matched on the 2 belt pulleys)
-nB

MBeige · #4 02-10-2007, 05:57 AM

Sounds like the power steering belt needs to be adjusted. When looking at it, look down at the belts and make sure they're all parallel to each other, and that all have no strange markings. Make sure too that you know what you're doing with the belts since it's very to strip/snap the tensioner bolts in the cold temperatures, especially that alternator tensioner.

FWIW, I bought new belts and had an indy mechanic replace them instead. Too much of a PITA if you're a beginner in this.

vstech · #5 02-10-2007, 08:32 AM

It is not a Terrible job, but you will hate the MB designers... you have to loosen the power steering pump, the A/C compressor and the alt to get the belts off. the a/c and PS can be loosened from above, the Alt has one bolt that is best accessed from below... three bolts hold each from moving. and each has a tensioner to loosen as well.
you are looking at about 3 to 4 hours to do it all... I would change the ps and A/C while you have them out.
enjoy!
John

#6 02-10-2007, 10:01 AM

Quote:

Originally Posted by vstech

you are looking at about 3 to 4 hours to do it all... I would change the ps and A/C while you have them out.

I is a bit of a PITA, but I don't know about 3-4 hours unless you run into a problem. Definitely replace all the belts if you are going to take the trouble to do this (the alternator/water pump belts are on the inside anyway). I think it took between 1 and 2 hours the first time I did it. The last time, I did it in a hotel parking lot in about 1/2 hour (barely got dirty). The trick is knowing all the tricks, like the best way to reach all the bolts. It also helps if you know nothing was over-tightened the last time. I also found that the OEM belts last longer than the "part store" brand belts, I don't believe the part store belts are actually the correct size.

If it's too much of a pain, just bring it to your indy, the labor should only be about $50.

networkboy · #7 02-10-2007, 02:01 PM

Any suggestions about the tightness of the belts?
Also, should I just tighten the loose belts to buy a week or so?
-nB

gatorblue92 · #8 02-10-2007, 02:06 PM

whenever i have needed to replace 1 belt on my 240D i have changed them all... they are cheap but a huge PITA to do... one of the only things i like better about my ford

vstech · #9 02-10-2007, 02:12 PM

I agree that 3 or 4 hours once you have done it, or if you have good mechanical skills is overkill, but the guy in the apartment asking about belts doesn't sound like mr goodwrench. figuring out which bolts to loosen, getting the right wrenches in there, removing everything, and putting the right belts back on can take quite some time in a apartment lot. I hope he does a bit of homework, and gets a list of the correct wrenches beforehand. of course that takes time too...

if they are slipping, and one is worn more than the other, it's unlikely you will get much time out of it, more likely you will drain your battery, due to the alternator not getting proper spin at speed.
bite the bullet, and change the belts. get the best belts you can, and make them tight enough that they flex less than an inch when you push in the largest span. if you are in a hurry, and the a/c belt is bad as well, cut the a/c belt, loosen the ps belt, and remove it, then slap on the alt belts, and tighten up.
have fun. I have done it twice now, and I don't look forward to doing it again soon.
John

vstech · #10 02-10-2007, 02:14 PM

oh, and soak the adjuster nut on the alternator FIRST and give it at least an hour to soak!!! that bolt is FLIMSY! and it is a bit of a pain to tighten the alternator belt without it...
John

networkboy · #11 02-10-2007, 04:53 PM

I just went out and PB'd all the adjuster nuts and mounting bolts. I have the FSM and read it thee times...
I bought a set of belts from fastlane, they are waiting to go on, just need a driveway that's dry to work in

I'm going to try and tighten up the alternator belt to get me by this rainstorm moving through. Should see sun by the middle of next week.

Quote:

the guy in the apartment asking about belts doesn't sound like mr goodwrench.

yeah I'm no goodwrench, but I'm not (help/hope)less either

Just constrained by my living conditions...

Speaking of which, just how much contortion is required if I want to do the whole thing topside?
-nB

#12 02-10-2007, 05:15 PM

Quote:

Originally Posted by networkboy

Speaking of which, just how much contortion is required if I want to do the whole thing topside?
-nB

I have never bothered to jack up the car when changing belts, but you will have to stick your head under the car to reach the bottom bolts on the alternator and AC compressor. It's not that bad, maybe 80 or 90% from the top.

vstech · #13 02-13-2007, 10:06 AM

didja git it?
if you are going to try and do it topside, disconnect the battery first. you don't want the ratchet hitting a wire on the alt and going pop...
you will need a set of 17mm wrenches, and a universal joint for the topside approach. the a/c uses same sizes, the ps needs 13 or 14 IIRC...you will need a pair of them for the ps, and a long handle box end to hold the nuts on the pulley end. and there are 3 bolts holding each part from moving. and one adjuster for each part.
that's all I can think of.
John