Hello everyone...

How do you adjust the fan belt on an old 955C, serial # on engine: 12A 781? The belt is very loose and it looks like the top pulley is on threads, so I guess there is some way to adjust it that way...but not sure. Thanks for your input!

Greg.

If you look at the back side of the rear half of the pulley you,ll see two flat plates(locks) with a bolt holding them and take them off and then the rear pulley half can be turned to make the pulley larger (tighter) for adjustment and when tight enough install the locks and bolts back in place so the adj. stays put.No big deal when you see how the adj. works.

To adjust the fan belt,remove the locks holding the adjustable rim of the pulley in position on the hub of the fan by taking out the fastening capscrews. Screwing the rim toward the radiator will tighten the belt.Be sure the locks are lined up with the slots in the hub before the capscrews are tightened.The adjustement is correct when the belt can be easily pushed inward at a distance of approximately 1 inch

crazy. .on these old critters that adjusting ring can be somewhat frozen up due to old dirt and rust. What I do is to apply some penetrating juice to the threads, remove the tabs, then with a chunk of aluminum and small hammer I start tapping the adjusting ring gently (but NOT where the locks fit) in the direction I want it to go. Every few taps, I'll rotate the fan and work my way around it. I've seen a very few that the adjusting ring could be tightened up by hand but most are frozen up to some degree or another. Be patient and let the oil do it's job along with the vibration from the tapping.

Do not try an air chisel - pulley will break

Thanks to everyone for your answers! Your help is very much appreciated!

One other thing: when you get the adjustment free back it all the way loose, paint the threads with anti-sieze and then procede with the adjustment. If there's norman wear in the pulley it's not going to stay adjusted all that long and you will have to tackle it again. You'll thank yourself then for the antisieze!