good people
i just replaced my water pump (day and half. never again i hope!) and now my belt is too loose. i had three different writeups from this site, on the procedure taped to the wall and followed them as much as possible.
ive reassembled everything and for some reason theres no belt tension. ive turned the adjusting nut all the way one way and all the way the other but no change. it was working fine before i removed it.

can someone definitively tell me about the long adjusting nut. is it supposed to be "mounted on" the backing plate so that adjusting it moves it relative to the backing plate, because mine just kinda seems to be sticking through the hole. which begets my question; how does it them adjust tension if it isnt pulling/ pushing on anything.

also, i dont see this arrow/ mark/ pointer that everyone seems to be mentioning. is it on the pulley, body of the tensioner, somewhere else???

id appreciate any advise. thank you.
im perusing the results for a search on "300e belt tensioner" as we speak, but i dont have time to go at this again. i absolutely have to be home by friday, im 400 miles from home in a borrowed garage and dead broke. thank you.

__________________
'O=00=O'
bmw 2002.
long live the legend

bump

__________________
'O=00=O'
bmw 2002.
long live the legend

First thing I would do is check your tensioner to make sure it works. Grab the tensioner pulley and move it to see if the rubber twists and returns to normal.
If it does, then the tensioner is OK.
As far as the pointer goes, it is on the top side of the tensioner assembly and when the tensioner is in the relaxed position, you are suppose to move the pointer to the left...at the starting point. Then proceed to tighten the tensioner adjusting bolt until the pointer moves to the maximum mark on the scale.

Make sure your lock down bolt is loose and then tighten it back down after adjusting the tensioner.

If all you did was replace the water pump, then everything should go back like it was.

Good luck,

Dave

In a bind, to get you home, you may be able to get some kind of lever in there to push the tensioner pulley to tighten the belt, then tighten the hold down bolt. Kinda like we used to do before there were belt tensioners.

This is what the part you are asking about looks like:

Attached Thumbnails

 

__________________
2012 E350
2006 Callaway SC560

Your tensioner may be shot. Do a search here, somebody took a failed one apart and determined that the poor design is prone to having the rubber material lose shape and distort early.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Make sure your belt is routed correctly. If not, you will not be able to tighten the belt to proper tension.

__________________
1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

I had to replace one for that exact reason. The rubber was torn and shredded and wouldn't hold tension.

One reason why I now no longer mess with the tensioner when doing any work under the hood. Not so much on the W124 but especially on the W210 I just "lift" the belt off the top pulley with my bare hands and leave the tensioner in place so as to disturb it as little as possible.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

I put the relevant docs from the service manual up at

www.pauldrayton.com/uploadfiles/merc/13-1202hw.pdf
www.pauldrayton.com/uploadfiles/merc/13-3200hw.pdf

Hopefully they will be of some help.

__________________
1983 240D Silver/Blue "Sadie", unknown miles. 100k miles on WVO single tank, converted to 2 tank about 10k miles ago, FPHE, Injector Heaters, Aux Fuel pump. Alcohol/Water injection. Frantz oil bypass filter
1992 300D 2.5 Turbo Green/Tan "Jade" 267K miles Stock.
1992 300D 2.5 tan/tan "Rocky" on 2 tank WVO. Pressure actuated Turbo "rat's nest" surgery completed. 197k miles

the tensioner wouldnt budge. i had to break out the credit card and buy a new one and a tensioner rod nut thingamajig.

i really do appreciate your help. really, i cant say that enough.

im slappin it together right now and trying to figure out the marks that are supposed to align with the planets when the moon is blue and pluto is resplendent over mars. or some crazy talk like that.

__________________
'O=00=O'
bmw 2002.
long live the legend

When you install it, put the pointer at the left line with the tightening bolt still a bit loose. Adjust the tensioning nut until the pointer is between the two center lines.

One trick that got me a few more miles (while the rubber part was still good) was to remove the tensioner, adjusting nut plate, and spacer that is on the shaft. You will probably find that the aluminum shaft flats are worn from the adjusting nut plate flats. Flip the plate over, and swap its position with the space, so that it now rides on an unworn section of the shaft, and is pushing with the opposite flat sides of the adjusting nut plate. If it's wear there, that will get you a few more miles.

That said, my last one was a case of sheared rubber inside the tensioner. Pushing the idler 30 degrees with the shaft held in a vice showed that it would not come back to its original position.

Gerry