dupp

Just transported my 91 D250 LE A/T on a 1600 mile trip from NY to Miss.

Great ride and all went well, however 1000 miles into the trip I noticed the serpentine belt (obviously orginal) was frayed and on it's last legs.

After installing a new NAPA belt I have noticed that the belt lines up perfectly with the excpetion of the AC pulley. It is one rib off toward the rear of the engine and shows slight wear due to its riding on the edge of the outer pulley grove.

My question: Is there anyway to adjust that pulley w/o having to realign/overhaul all of the pulleys/tensioner.

Might be much ado about nothing, but you folks know these vehicles hearts and souls so I go to the source.

Many thanks,

Mike

stuart

I think you'll find you are just one groove off on the a/c pulley.Loosen the tensioner and move the belt foward one groove. If the old belt rode true the new one should also,unless the a/c compressor is loose on it's bolts.

wannadiesel

A bad tensioner will cause the belt to walk. If you put the belt on right and it jumps back to where it is now, replace the tensioner.

MCummings

Excellent advice.

Exactly what I would have said. I second the motion.

Merrick

Monty

Mine did that for a year and I couldnt find the cause of it. I changed 3 belts, each time after about 3 hours running they would walk 1 rib off. If you let it go like this with the same belt, the belt would just keep on moving over one more after it frayed off one rib.

I changed the belt tensioner, water pump and inspected the fan pulley/bearing very good. When I went back with the outside gear housing after checking the KDP and installing a new front seal and torqing the crankshaft pulley, it quit.

My guess is that the crankshaft pulley was not aligned, or they were not torqued to proper spec.

Yours may be as simple as a belt tensioner like the others mentioned. But, it might be a good idea to check the crank pulley bolts. I believe they torque to 101 ft. lbs.

dupp

All Respondents:

Many thanks for the advice. I had "reinstalled the Serp belt when it "walked" back one rib, but the same movement happened once I started the cummins' up.

Will check into replacing the tensioner. Any info. on best place to find one? Would NAPA, Advance Auto, Autozone carry tensioners.

Once again I value your input.

Mike

furious70

incidentally, my truck has always done this too. Set the belt straight and it immediately walks 1 rib back, but stays there. After owning it for 40k mi, it is finally starting to fray that end a little bit. I didn't see anything visibly loose either, but all that stuff is under a lot of tension, hard to say which part may cause the walking.

dupp

furious 70-

You make a good point. When the Serp belt was frayed and cracked I'm sure it was the original 13 yr. old 75K orig miles belt that game with the truck when new. so perhaps the new belt will get a bit frayed but also last 75K which I could certainly live with.

If this is my biggest concern with the new/used '91 Cummins I think I can live with that.

Appreciate the insight.

Mike

wannadiesel

I've had good luck finding parts at my local truck parts store. Some truck parts stores don't want to deal with a guy off the street, but this one doesn't mind as long as the money's green.