Serpentine Belt Tensioner (early / manual style)

[ALL500]

So, my new lower harness is in, but I still barely made it home from the mechanic from hell's shop (last time there ever!)

Before I isolated the harness issue, he said the alternator was bad (it's good) but I have a rebuilt one (that he could swap for a minimal fee).
Turns out, as I did my lower harness, he did not swap the alternator. But oh, he did have an assistant 'tighten the belt'.

Well as it turns out, seems like tightening the belt must be done very carefully on the 1992 500e? From what I gather, there is an order to follow before any adjustment can be made?
My belt is literally hanging off, about 2-4 inches of slack, I'm not sure how I made it home - I was close to stalling out at red lights and squealing everywhere.

The nut (with the plastic arrow indicator) loosens but nothing happens when it is tightened. The plastic arrow indicator was 180 degrees from the marker section.
The top screw-thing, with the rod beneath it, does nothing but shift from left to right when adjusted.

Is there a how-to on this and potential replacement that I am missing? Or did the mechanic not break it and I'm just doing something wrong?
It was fine before, no belt problems. The first picture is after I moved the plastic indicator back up. (Is the arrow even facing the right way?).
*Edit* It's not is it?? ArRRggh.

 

[TerryA]

Re: Serpentine Belt Tensioner

Another reason to do your own work if possible. I think some mechanics create more work for themselves.

 

[ALL500]

Re: Serpentine Belt Tensioner

At least he let me swap my lower harness in his muddy, wet, chemically yard...

 

[Klink]

Re: Serpentine Belt Tensioner

Another reason to do your own work if possible. I think some mechanics create more work for themselves.

I've been around mechanics, service advisors, and shop owners my entire working life. Believe me, you are actually giving us way too much credit by imagining that...

 

[gerryvz]

Re: Serpentine Belt Tensioner

There is a HOW-TO on replacing the serpentine belt, but it is primarily for the later (1993-1994) cars with the automatic belt tensioners, that make the job much easier. 1992 & early 1993 cars are a bit more involved with the process. I'm attaching the factory procedure on serp belt replacement and adjustment for the early cars.

http://www.500eboard.com/forums/showthread.php?t=7375

Cheers,
Gerry

 

[ALL500]

Re: Serpentine Belt Tensioner

Thanks a lot Gerry. So it's safe to say that with no belt-tightening happening when the bolt and rod are adjusted, that I need a new tensioner?

 

[gerryvz]

Re: Serpentine Belt Tensioner

I've never had a car with the early-style tensioner, so I'm not up on how they work. GSXR or Klink can likely fill you in on what is needed. However these tensioners can/do go bad and need replacement.

 

[samiam44]

Re: Serpentine Belt Tensioner

I believe it works like the M103 tensioner. You are applying tension to an arm which preloads rubber. The rubber is in torsion, which by MIL-rubber handbook is a big-no-no. If he's got slack, it maybe a bad tensioner. I think MB's idea was the rubber would act as a spring and dampener.


Make sure the pointer is seated... boy I don't like those. I know some of those later-early cars had a front timing cover which would take the later style tensioner.


M

 

[Eno]

Re: Serpentine Belt Tensioner

I am in the process of ordering/changing this above described part for my 1992 500E with part #: A119 200 02 70.
It is cracked/broken in the frame. I am gonna decide between the MB OE part or a Canadian brand. Thank you guys for sharing your exeperience and knowledge.

Kind regards,

Eno

 

[ALL500]

Re: Serpentine Belt Tensioner

Not sure how to check if anything is cracked or broken, until I take it apart, can't see much there. Eno, what is the Canadian brand you are looking at? From all accounts this is a part to go to the dealer for?
Is there a way to diagnose for sure weather the part is actually broken, without taking it apart?

 

[gsxr]

Re: Serpentine Belt Tensioner

1) You MUST loosen the large pivot bolt before adjusting belt tension, then you must re-tighten it afterwards.

2) There is no way to tell if the tensioner is bad without removing it and checking on the bench in a vise (per FSM procedure), unless it's REALLY hosed in which case you may be able to tell by loosening / partially removing it... but at that point, just take it off.

3) Be careful buying replacement tensioners, last time I checked the aftermarket no longer carried OEM, only junk stuff that I wouldn't trust. If you can't find a name brand, buy OE. From a quick look (p/n 119-200-02-70, $334 dealer list, ~$250 discount) the only aftermarket brands currently available are Uro (junk) and Febi (crapshoot). The Febi is ~$100, if you gamble on it, please post photos so we can compare to the OE/OEM unit.

4) The order of assembly is critical, make sure the washer/adjuster on the back side is not reversed. And DO NOT over-tighten! It's better to under-tighten, which is easily cured, than to over-tighten and possibly destroy a new $250+ OE tensioner.


All of the above is why I really, really like the late-style automatic spring-loaded tensioners. From your photos it appears your car is a late 1992 model with the appropriate mounting boss cast into the timing cover, so it's possible to convert, but it's a pretty complicated upgrade. Another forum member documented the process in a thread with pictures, it requires some part swapping plus drilling / tapping the timing cover boss. If the car is a long-term keeper I'd consider this, otherwise just replace the blasted rubber thingy.

 

[mercepor]

Re: Serpentine Belt Tensioner

I had the same prb with my tensioner, yours is also broken, the rubber is cracked, we can see it on your picture.
If you overtighten these old tensioners, you can crack them easily.
On your photo the rubber seems to get out from the frame, it is like an "omelette"....
You should change it and just follow the factory procedure when tightening.
Probably your mechanic broke it.

 

[ALL500]

Re: Serpentine Belt Tensioner

Thanks Dave,

1) The large pivot bolt is the top one attached to the rod? If so, I loosen until it can freely move left/right?

2) Ok.

3) I definitely don't want any URO junk in my car, the Febi is not inspiring.

4) Check)

5) I think I'll stick with a carefully installed, unmodified set up.

 

[ALL500]

Re: Serpentine Belt Tensioner

Ok, thanks mercepor - I'm understanding what I'm looking at a little better. Yes, this is the last in a long line of fudges from the 'mechanic'. He once told me (when I first had harness issues) that I should swap the motor with one of his junked 300e's. (drumroll/cymbals). True story.

 

[gsxr]

Re: Serpentine Belt Tensioner

Thanks Dave,

1) The large pivot bolt is the top one attached to the rod? If so, I loosen until it can freely move left/right?

No. The pivot bolt goes through the middle of the tensioner, it's big, either 17mm or 19mm hex head. This needs to be loosened (say, 1/2 to 1 turn) and then you adjust tension via the rod, which has a 13mm (?) hex head and possibly left-hand thread. It's been a few years since I fiddled with one of these and I can't remember details offhand.

Have you tried searching the forum? I thought there was a thread or two on this manual tensioner but it may have been 3-5 years ago...

 

[ALL500]

Re: Serpentine Belt Tensioner

Great! Typing in 'manual tensioner' got me the info I need. Indeed, what an interesting design they have here...

Spring-tensioner upgrade? Hmmm...

 

[ALL500]

Re: Serpentine Belt Tensioner

I found this video of the tensioner replacement on an R129. I'll try to document the process as best I can with pictures when I get to it.

https://www.youtube.com/watch?v=_3juL9PixuU

[video=youtube;_3juL9PixuU]https://www.youtube.com/watch?v=_3juL9PixuU[/video]

 

[Eno]

Re: Serpentine Belt Tensioner

I was told by a friend of mine about the belt tightener/tensioner with the name brand 'Litens', a Canadian product, which he said are as good as INA. I agree this is a delicate and expensive part. GSXR is right, 250USD is the OEM MB Ina.
A technical inspection of the serpentine belt tightener by an authorised MB service told me that I have a broken belt tensioner. When I remove it I'll see in condition it is.

 

[gsxr]

Re: Serpentine Belt Tensioner

Had time to do a quick search, here are some relevant threads:

http://www.500eboard.com/forums/showthread.php?t=4475

http://www.500eboard.com/forums/showthread.php?t=8064



Late-style auto-tensioner retrofit info:

http://www.500eboard.com/forums/showthread.php?t=5677

 

[ALL500]

So I bought the tensioner from Universal German Auto Parts Inc. (eBay store, $140 USD + shipping ) in Sun Valley CA:
http://stores.ebay.com/Universal-German-Auto-Parts-Inc


I asked them first if it was manufactured in China and they were highly offended. Made in Japan and supposedly top quality.
So far so good. Time will tell.

When doing the job, be sure to screw the top nut adjuster all the way down before re-installing.
I made sure the big bolt was loosened before adjusting the tension, then tightened after.

I should probably have worn gloves.

 

[gsxr]

I've never heard of any M119 tensioner made in Japan. Was there are brand name on the box or bag it came in?

Very odd they list no brand name in their listing:
http://www.ebay.com/itm/w140-w124-w129-500SL-500SE-400E-500E-Belt-Tensioner-/160509056239

 

[ALL500]

Maybe they're taking me for a ride? I dunno. No brand name on the box/package or the tensioner either.

 

[zooklm]

I want to share my recent early tensioner replacement. I purchased a Lasso brand tensioner off of Amazon for $130 and a Mercedes 8 rib belt. When tensioning the new tensioner, I came to the realization that I was missing the pointer. I found the part number and cost (approx $25) but did not want to order and wait. Therefore, I used nail polish to mark the snug but at rest location and then watched it move as the tensioner was tightened. Here are a couple pictures. The camera angle is not directly aligned with the marks, though. I will likely look get a pointer at some time in the future and install it when messing with something else on the engine.
Lee

 

[Trae]

OK parts people. . .looks like my old tensioner is at its limit and must be replaced soon.

EPC says part #
A 119 200 02 70

Should I pay $240 with Gainsville Mercedes, or is there another QUALITY option?

 

[gsxr]

OK parts people. . .looks like my old tensioner is at its limit and must be replaced soon.

EPC says part #
A 119 200 02 70

Should I pay $240 with Gainsville Mercedes, or is there another QUALITY option?

Laso had offered a Made in Germany tensioner a few years ago that appeared to be a quality item. But their current tensioner does not say where it is made, and there are zero markings anywhere on it to indicate anything at all... but it sure looks like it's made somewhere else now. Photos of both at this link. For a car you care about, I'd shell out for the OE/dealer item. On a budget, give the Laso a try. Not sure what the Febi looks like, but I have a feeling it isn't reboxed OEM. Then again, with FCP's lifetime warranty, you could take one for the team, try it out and let us know!!

 

[Trae]

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[Trae]

Looks like OE will be the way to go. . . can't stomach putting Febi on any of my cars.

$240 from Gainsville Mercedes

 

[JC220]

I had got a INA tensioner for my 500E a year or so ago. I think INA is the OEM manufacturer.

 

[gerryvz]

INA is good stuff and on the Santa “nice list”.

 

[Trae]

Just did this job today.

Part still $240 -A 119 200 02 70
I ordered OE.

Tools Needed:

13mm socket
19mm socket
8mm to remove upper radiator hose

FIRST, take pictures so you can refer to the orientation of the tensioner in relation to the belt.

I placed the car on ramps and removed upper radiator hose from radiator to make room by clamping the hose and bending it out of the way. I also removed the black plastic cover above the engine.

Then, I loosened the 19mm bolt that went through the center of tensioner.
As you remove the tensioner, keep your hand on the back side of tensioner to keep the adjustment rod and washer from falling into the abyss.

Note how the adjustment rod fits on the tensioner.

Install new tensioner with the 19mm bolt, but keep the bolt loose.
Gently adjust the rod with 13mm socket to desired tension. (My pointer had been lost long ago.) I elected to keep the belt just hand tight for now.
After adjusting, book says to tighten 19mm bolt to 100nm, or 74 ft. lbs., however, I stopped short of that much torque and tightened to 90nm because I didn't trust my torque wrench.

 

[nocfn]

Pics or it didn't happen.

 

[Trae]

Pics or it didn't happen.

Yea, I am pretty bad about that.

 

[nocfn]

Just messin where I shouldn't be messin….

Nancy Sinatra - These boots are made for walkin

 

[Trae]

Took the 92' Renntech for a 25mi. spin after the new tensioner and she seems happy!

I had been dreading this job for years but when the old tensioner failed, there was no more putting ot off.

Turned out to be a "not so scary" job however.

 

[Federico80]

Took the 92' Renntech for a 25mi. spin after the new tensioner and she seems happy!

I had been dreading this job for years but when the old tensioner failed, there was no more putting ot off.

Turned out to be a "not so scary" job however.

I'm waiting on my new tensioner and adjuster to show up. Replacing the belt this past week the head of the adjuster flew across the engine compartment lol

 

[pablo2696]

Hello all,

I have just received a new belt tensioner (LASO 119-200-02-70), and I'm encountering some issues while trying to install it. It appears that the insert where the rod washer and the other washer go into is rotated in the wrong direction (angled towards the pulley). When I compare it to new units from the internet, it seems that the insert is rotated at some angle. Could someone please confirm whether the tensioner is faulty before I proceed with the return?

Thanks!

 

[gsxr]

That does appear to be a defective tensioner. I assume it's not possible to install the tensioning rod with the "wrong" position... if that is the case, I'd return for exchange.

 

[pablo2696]

That does appear to be a defective tensioner. I assume it's not possible to install the tensioning rod with the "wrong" position... if that is the case, I'd return for exchange.

Thanks ! I just replaced it with a new unit that appears to be in good condition.

 

[pablo2696]

Hello all,

Unfortunately, while adjusting the tensioner due to it being too loose, I ended up snapping the large 19mm pivot bolt... I'm at a loss for what to do next. Does anyone have any suggestions or has anyone else experienced this before?

 

[gsxr]

Hello all,

Unfortunately, while adjusting the tensioner due to it being too loose, I ended up snapping the large 19mm pivot bolt... I'm at a loss for what to do next. Does anyone have any suggestions or has anyone else experienced this before?

Uh-oh. You'll have to take it all apart and remove the broken bolt, and replace with a new bolt.

Keep in mind the torque spec for that 19mm bolt is only 100Nm which is not a huge amount of torque, it would typically require far more (like, double or beyond) to actually break the bolt. Always use a torque wrench.

 

[pablo2696]

Uh-oh. You'll have to take it all apart and remove the broken bolt, and replace with a new bolt.

Hi Dave,

Thanks for your inputs. Just to clarify, when you say "take it all apart" you mean the front engine cover?

 

[gsxr]

No, sorry... I mean take off the belt tensioner so you can extract the bolt. I think it fastens into the AC compressor bracket? Might need to remove a bunch of stuff that might be in the way.

 

[pablo2696]

No, sorry... I mean take off the belt tensioner so you can extract the bolt. I think it fastens into the AC compressor bracket? Might need to remove a bunch of stuff that might be in the way.

Hi,

I've already removed the broken bolt after essentially dismantling everything at the front of the engine, except for the timing covers. Since removing the crankshaft pulley was necessary to get one bolt off the AC compressor bracket, I ended up replacing the water pump, crankshaft seal, and other components.

After reassembling everything and driving the car for 2 days without any issues, the belt became loose. The Febi tensioner has failed (less than 3,000 km), and it's practically new… I'm never buying a Febi tensioner again.

After dealing with a defective brand-new LASO and the Febi product not even lasting 3,000 km, I'm not going to risk it again. I will buy the genuine Mercedes part this time.

 

[gsxr]

I've already removed the broken bolt after essentially dismantling everything at the front of the engine, except for the timing covers. Since removing the crankshaft pulley was necessary to get one bolt off the AC compressor bracket, I ended up replacing the water pump, crankshaft seal, and other components.

Nice work! You shouldn't have to mess with the front of the engine for a long time.

After reassembling everything and driving the car for 2 days without any issues, the belt became loose. The Febi tensioner has failed (less than 3,000 km), and it's practically new… I'm never buying a Febi tensioner again.

That's insane. Thanks for sharing this (depressing) information. Hopefully other forum members will see this and avoid Febi (and Laso!).

After dealing with a defective brand-new LASO and the Febi product not even lasting 3,000 km, I'm not going to risk it again. I will buy the genuine Mercedes part this time.

Prices have dropped on the OE/Genuine tensioner. It is currently $250 MSRP, $185 at Naperville, $170 at Laredo:

1990-1992 Mercedes-Benz Belt Tensioner 119-200-02-70 | MB OEM Parts

1990-1992 Mercedes-Benz part # 119-200-02-70 - Belt Tensioner

www.mboemparts.com

119-200-02-70 - Belt Tensioner 1990-1992 Mercedes-Benz | MB Parts Source

Factory Direct Belt Tensioner (1192000270) For Your 1990-1992 Mercedes-Benz Vehicle. Up To 35% Off On Every Order And Guaranteed Fit When You Enter Your VIN!

www.mbpartsource.com

Anyone who has a manual belt tensioner that is old/original (or, unknown age/miles)... might want to buy a new OE tensioner and put it on the shelf for when the old one finally dies. No telling when this might go NLA (it is still available as of now).

 

[pablo2696]

That's insane. Thanks for sharing this (depressing) information. Hopefully other forum members will see this and avoid Febi (and Laso!).

Prices have dropped on the OE/Genuine tensioner. It is currently $250 MSRP, $185 at Naperville, $170 at Laredo:

Hopefully, I won't have to deal with anything there for a couple of years, and I've even upgraded to the newer style water pump. As for the tensioner, I purchased it for $180 at the Benzel-Busch dealership in Englewood, NJ. If it fails in the next couple of years, I will definitely do whatever is necessary to switch my M119 to the newer style automatic tensioner with the 6-rib belt

1990-1992 Mercedes-Benz Belt Tensioner 119-200-02-70 | MB Online Parts

 

[gerryvz]

I will never know, after REPEATED warnings and discussions here on this forum over many years, who people continue to buy cheap, inferior parts like Febi, Meyle, URO Parts, etc. Please don't. Just don't.

Even a used factory part is going to be better than this trash.

 

[pablo2696]

I will never know, after REPEATED warnings and discussions here on this forum over many years, who people continue to buy cheap, inferior parts like Febi, Meyle, URO Parts, etc. Please don't. Just don't.

Even a used factory part is going to be better than this trash.

For some of us living in third-world countries, there are few local options (if any) for parts. In my case, the previous tensioner failed, and I urgently needed a replacement. The only local parts store had just two options (the defective Laso one and the Febi).

This time, I purchased the genuine part, but I have to wait about three weeks (without being able to use my car) for it to arrive in Costa Rica.