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Old 05-23-2002, 07:21 PM
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91 190-E 2.6 Auxilliary Belt Tensioner

I have just replaced the water pump on my '91 190E 2.6. I got it all back together with no leaks. Short-lived good news!!

I lost the tension on my auxilliary belt after a 100 miles of driving. I tried to adjust it and from reading other tech help on the 300 I realize that I hadn't loosened the 19mm bolt on the idler pulley arm and I stripped the tensioner rod nut trying to adjust it. I have taken it all apart again. I bought a new tensioner rod and nut. Now I'm not sure which way the tensioner rod and cam attach to the idler arm. It can be turned with the rod between the cam and the tensioner or with the rod next to the mounting bracket. Which is correct or does it make a difference. Also, when I had the idler arm off I could move the idler arm about a half inch before it seems to tighten up. When it does tighten it seems to have good tension.

Should the idler arm tensioner (19mm) nut be loose when I put the belt on? Should I also have the tensioner rod nut loose? Help? I don't want to take it apart a third time.
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Old 05-24-2002, 12:22 AM
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Join Date: Apr 2000
Posts: 412
The rods on the tensioner strip out and is very common. To replace the rod the complete tenisioner assembly has to come out. The means power steering pump and brackets. I have always had to remove the radiatior to work on the front engine on my 190 2.6. Thats if you don't want to damage the radiator (very expensive). The radiator removal takes more than half the time of the other repair. I have done the water pump, scary but when done quite a sense of accomplishment. I did not replace my tensioner but replaced the rod when I did my water pump. My tensioner started acting up a few months later but I can live with it for now.
My tensioner rod was stripped but I rigged it to tighten by placing a spacer where the adjuster is to catch some good threads on the rod. I used a 1/4 inch U bolt that is used for cables on garage doors. I used a Dremel with a grinding bit to make it fit. It worked and would have contined to work. Hope this helps.
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T
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Old 05-28-2002, 10:28 AM
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Thanks for the pointers. I went ahead and bought a new tensioner rod and also a tensioner. I don't want to have to take it apart again soon.

Do you recall which way the rod cam attached to the tensioner? It seems to be able to fit with the connector end of the rod either between the tensioner and the cam or between the cam and the inner bracket face. Maybe it doesn't make any difference but the way I have it the tensioner nut doesn't seem to want to fit in the rounded area of the hole where the nut comes through.
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Old 05-28-2002, 11:22 AM
csnow's Avatar
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Join Date: May 2002
Location: Mass
Posts: 1,127
A few 'shop tips' when working in this area:

Taping a piece of cardboard to protect the radiator from errant 'wrench swings' and slipping prybars is cheap insurance when performing this work.
I learned this lesson the hard way...

Also, I decided to cut my 1-piece fan shroud in half for easy removal without having to remove the fan.
I then reattached the 2 halves to each other with wire ties.
This is a huge convenience upgrade, and knuckle-saving measure.

Put some anti-seize on the threads of that tension adjusting mechanism to save yourself aggrevation in the future.
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