W124 Belt Tensioner Contraption, over $140 to replace? - PeachParts Mercedes-Benz Forum

i-osprey · #1 09-03-2009, 11:51 PM

Is this about right?

I'm not for sure that I need to replace it but this is basically what I came up for the tensioner, damper and spring.

When I shut off my engine there is a metallic clank/ping often and I used to worry it might be timing chain slap but I've checked that and it's definitely not it.

Could it be my belt tensioner apparatus?

Wodnek · #2 09-03-2009, 11:56 PM

Yes it could. You just need to replace the "shock looking thing" You can get a beck or meyel for under $60. You can do yourself pretty easy. Your jack handle will serve to put in the hole at the top to hold everything in place.

i-osprey · #3 09-04-2009, 12:06 AM

Well, I found a Stabilus-Boge one for $24.

i-osprey · #4 09-04-2009, 12:46 AM

I just went outside and checked mine.

I took out the upper mounting bolt and tried to extend/compress the damper.

I could extend it but I couldn't compress it by hand.

It took eight minutes(I timed it) for it to compress on it's own with me helping a little along the way.

Is this normal?

Does anybody have any experience with a new damper?

All the dampers/shocks I have messed with would start rebounding immediately.

Another thing, it did nothing when I took out the bolt.

I actually had to pull up on it to get it to extend and then it wouldn't compress.

Wodnek · #5 09-04-2009, 08:03 AM

the simple test to see if it needs replacement is this. Look straight down at it. Does it run at near perfect vertical? Or does it slant to the top a bit?

If it slants, it is not doing its job, replace it.
When it starts to slant, your serpentine belt will not track right and will start to wear fast. Leading to a possible overheat situation. The death of many a 603 head. Some recomend replacement every 2 years just as a precaution.

#6 09-04-2009, 08:03 AM

I'm sure that the situation can exist, but I've never seen the hydraulic damper alone be the problem with the belt tensioning system. If it were mine and I depended on the car everyday, I would do a belt tensionerectomy and replace everything. Given the PITA of replacing this contraption I would also inspect the belt closely and if there were any cracks at all I would replace it while everything is apart.

Also ANY TIME you have the belt off for ANY reason, make SURE that you spin every pully in sight to make sure that it spins freely and smoothly. It's such a PITA to get the belt off and on, take advantage of this opportunity to check everything. If there is a bearing or accessory that needs attention, attend to it before you put all this back together.

This belt tensioning system is one area where I feel that MB over engineered to an extreme fault. There are zillions of other cars with extremely simple serpentine belt tensioning systems that allow you to remove and replace the belt in literally about three minutes and they work just fine.

My $0.02,

tombance · #7 09-04-2009, 09:11 AM

In my case the hydraulic damper was a bit problem. Clearly all of its fluid had leaked out so it had damping ability (the new ones are VERY hard to push/pull - in both directions), and the bushings were very sloppy.

The result of these two problems was that at idle the pivot arm would move back and forth, and the belt would slap around in a very noisy fashion. In the end this resulted in a cracked mount for the power steering pump, throwing the belt, getting the engine temperature into the red for 30 seconds, and a tow home. I had to replace the entire power steering pump, the tensioner shock, a lot of coolant that had overflowed, and my belt. Thankfully the engine wasnt damaged.

tombance · #8 09-04-2009, 09:13 AM

To answer your question osprey, a brand new damper is VERY difficult to move, but it should be the same in both directions. So it sounds like your one is broken. I would just replace it, made my engine infinitely quieter at idle.

sixto · #9 09-04-2009, 10:33 AM

I'll take another jab at i-osprey - how about a KYB damper?

You don't need to replace the spring unless it's physically broken.

Besides testing the pulleys for noise and syrup smoothness when spinning, check that they don't wobble about the spin axis. Check also the tensioner arm. If it clicks when you move it, the bearings are shot and not long for the world. If it wobbles any amount about the pivot axis, replace it immediately. Save the thick washer between the tensioner arm and front cover. There is a sealant spec for the threads of the big bolt though the tensioner arm. IIRC, torque spec is 50 lbft.

The sound you hear when you shut off the engine might be more related to worn engine mounts. Run the engine for a few seconds without the belt and see if you hear the sound when you shut off the engine.

Sixto
87 300D

i-osprey · #10 09-05-2009, 01:14 AM

Will do sixto,

I have replacement engine mounts on hand and will be replacing them this weekend anyway.

I have noticed that at idle the tensioner arm is definitely bouncing up and down a bit.

Also, the damper is definitely SLANTED, not completely upright.

Sounds like I at least need to replace the damper.

Thanks for the help.

Oh, KYB's are a very good deal for the money....

a2t · #11 09-05-2009, 03:45 PM

yeah $140 is about right. replacing that damper is not as simple as its been suggested. You will quickly find that the lower bolt cannot be removed without 1st removing water pump pulley, which 1st requires fan clutch to be removed, which 1st requires entire rad to be removed. are we having fun yet??!?@

so...i would seriously consider replacement of all the following, given the pain in ass factor :

1. serp belt, and keep old in trunk!
2. tensioner w/wheel
3. damper
4. fan clutch (just use the 606 clutch, its alot less exp)
5. lower rad hose, since you'll never be able to replace it with fan in
6. check spring, if its ques replace it, if not, keep it. ive had 1 break and it dents bottom of hood and leaves you stranded so nows the time.
7. clean/flush rad or if you have the jack just replace it with a new behr unit

oh and more friendly advice :

when replacing the tensioner, give the dealer your VIN and determine the exact type of tensioner you need, and also the spacer that goes behind it. There were 3 different styles. There were 2 different spacer thicknesses. The spacer is critical because without the proper 1, the belt will not ride centered on the tensioner wheel - the wheel is about the exact width of belt, so no room for misalignment. if any portion of the serp belt is hanging off tensioner wheel, the serp belt will shred itself at midnight the next time you are driving on deserted road, and likely take out the following other components when it does - upper rad hose, vac lines, lower rad hose, a/c comp elec wiring...

ask me how i know all of this .... bang head into wall repeatedly ...

as for comment on simplicity of the serp belt tensioner set up on these 124's...MB was quilty of overdesigning a whole lot on that car (ie, 5 link rear suspension with 200 bushings, acc with multi-hundred page repair manual) but I think the serp set up is rather good. You can repalce the belt in 10 min, you just need to wiggle it between fan and shroud. not fun but not impossible either, ive done it side of road with nothing more than tire iron on more than 1 occasion. at least theres not 3 v belts all with pivot tension all squeeling simultaneously. theres many cars much worse!

sixto · #12 09-05-2009, 04:44 PM

IIRC if you remove the tensioner pulley you can swing the tensioner arm to expose the damper lower attachment bolt. Further IIRC that allows you to replace the tensioner arm without removing the fan. I can get to the tensioner arm bolt without removing the fan. Takes a specific length 12mm hex bit in a 603. I imagine a 602 is more forgiving.

But that's just bragging and something to consider when stranded. Certainly do what a2t recommends to allow a thorough inspection.

Sixto
87 300D

a2t · #13 09-05-2009, 10:31 PM

i thought i tried that, but the bolt was too long to come all the way out of the damper, and it hit the water pump pulley. i guess its possible that i have an "aftermarket" bolt thats longer in there, who knows. sixto knows these things far better than i do!

babymog · #14 09-07-2009, 01:47 PM

I've done it on an '87 also with the fan and radiator in place.

babyjames · #15 09-07-2009, 02:11 PM

If you pull the shroud away from the radiator, there is enough room to reach in there with a long-handle 3/8 ratchet and 8mm stubby hex socket (I can get you the SnapOn part no. on Wed.) and remove the fan with the radiator in place. Don't remove the belt/tensioner until AFTER you loosen the fan - unless, of course, you have the special wrench that serves as a counter-hold on the fan clutch. I just put a little extra tension on the belt to keep things from turning when removing the fan-fixing bolt.

Jay.