Fan Belt Problems

[JIM KELLER]

Prior to our trip to POG III in Kerrville I noticed some missing teeth on two of my belts. I replaced them and all other belts at the same time. After our return a belt inspection revealed the same two belts were missing some of the teeth again. All other belts without teeth are fine. These two belts go around the harmonic balancer and then the alternator and over the road a.c. compressor. The belts are AX74, 1/2 x 76'' long. I am considering A74 belts this time which are the same size and width without the notches or "teeth."

My question is, why are these two belts the only belts on the bus with notches and why are they the only belts having a problem. It was always my understanding notched belts were designed to go around small diameter pulleys so there was less stress on the belts. None of the pulleys on our engines are small so I am wondering why notched belts are being used in this application.

Anyone have any ideas why Im losing my "teeth" ?

[dale farley]

Jim, The most logical solution for losing teeth would normally seem to be "Old Age", but since you said you just replaced the belts, maybe that is not the problem this time.

I too, find it strange that you are losing teeth on two belts. Have you checked to see if there is a small imperfection in the pully (a raised piece of metal, etc.) that may be tearing the belt? Not likely if you have two different ones doing the same thing, but this is strange.

[win42]

Jim: I would inspect the pulleys as dale suggested first. Then measure all the pulley sizes and call Gates Rubber in Denver and run it by their engineering.

[JIM KELLER]

Jim, The most logical solution for losing teeth would normally seem to be "Old Age", but since you said you just replaced the belts, maybe that is not the problem this time.

I too, find it strange that you are losing teeth on two belts. Have you checked to see if there is a small imperfection in the pully (a raised piece of metal, etc.) that may be tearing the belt? Not likely if you have two different ones doing the same thing, but this is strange.

Dale, Thanks for the input. I have checked the pulleys and they look o.k. There could be a slight miss-alignment of the A.C. Compressor but it is hard to get my head in alignment with the belts to be sure. If so it is very slight. Guess I will wait for "JON" to step up and comment on this problem.

[JIM KELLER]

Jim: I would inspect the pulleys as dale suggested first. Then measure all the pulley sizes and call Gates Rubber in Denver and run it by their engineering.

Thanks Harry, How does your California girl like her new bus ? Did it keep her cool on the return trip ?

[Jon Wehrenberg]

FWIW my belts are without teeth.

[rfoster]

Jim K: This is a SWAG or a hunch at best. I recently experienced a terrible, terrible noise coming from my engine when I fired up the engine while in Hotlanta the other day. We had been dry camping the night before and had shut the engine off with the OTR bus air still on. Due to the air regulator leak over the engine door my belt air bags (bellows) loose their air pressure overnite. As a result the air was down in the bellows that tighten the belts and the bus air was on so when I fired up the engine the belts were not exactly slipping but skipping on the pulleys making a terrible noise. jerking, and possibly knocking off some teeth. I immediately shut off the engine and a/c and inspected the belts and yes they were too loose. I fired the motor again with a/c off and let the air build in the bellows and then all was well. I since ordered a new regulator and three new bellows from prevost (on Sale for 25 lewbucks each). Will install this weekend. Check it out on yours and see if the belts are tight from a cold start. This is still no answer as to why the a/c belts have teeth. I even bought new ones with teeth for spares. I would still like to know whey they have teeth.

[lewpopp]

While were on the belt subject, the belt that goes to my dash air is presently useless because I was told my compressor was shot. Is there any reason I need to run the compressor with that belt? I'd like to cut the belt and go from there until I replace the compressor.

Also, someone said I can replace that compressor with a compressor off of an old Ford pickup. Does that sound right? Before I did that I would make sure the lines running forward were without leaks.

Lew

[dale farley]

Lew, If I were you and the compressor wasn't working, I would definitely remove the belt. No use in turning it for nothing.

If your compressor is like mine, it does look very similar to other compressors I've had on vans in the past. I would think that any compressor that you can make fit the spot would work. I would also convert it to 134A (or later version) freon when I replaced it.

[garyde]

I still have most all of my teeth.....and my fan belt does not have any.

[truk4u]

Hey King, that bottom bellows is a bi... to get the bolt in. I used a deep socket with some tape to hold the bolt in place. You'll see what I'm talking about when you get to it.;) That will be $5.00 for the tip please..

[Joe Cannarozzi]

Rodger

Our regulater for the belts was leaking pretty good and I was able to completly stop it by tightening the bolts at the flange for the diaphram.

[BrianE]

Lew,

FYI. I replaced my dash air compressor after talking with Don Arlett, the Mira Loma CA Prevost Service Mgr. He suggested that it probably wasn't necessary to convert to R134a refrigerant but to use an R12 substitute which is much cheaper and will not require changing any hoses. He also told me their new compressors have a much improved shaft seal which is why they usually fail. The cost of the new compressor was around $240 and we are now using "AutoFrost" http://www.refrigerantsales.com/autofrost.html
instead of R12. The system has worked perfectly since we made the change last fall.

[JIM KELLER]

Hey Brian, Whats up with this post to Lew about Freon on my Fan Belt Problem post. Just for this you should slove my problem or I'm turning you into the Thread Police !

By the way, How are you and Beverly.

[JIM KELLER]

New belts installed. Found no problems with any bearings or pulleys. I installed both new belts plus the three that run the transmission for the fan blades with the belt names and numbers lined up together. After running the engine for a few minutes to check alignment I shut it down and discovered none of the names or numbers on the belts were even close to each other ! Wonder whats up with that. I dont understand how matched belts running on the same pulleys can turn at different revolutions.

[Jon Wehrenberg]

Because while the belts are probably very close to exactly the same, their overall length can vary by a few thousandths, and thus after some engine running time nothing will be aligned.

Every time I stop the coach, I have to go in the back and line mine up again, just in case someone wants to see my engine.

Looks like you will have to do the same.

[truk4u]

Jim,

Make sure you have the correct pressure set for the bellows, it's above the door.

[Jerry Winchester]

I just used a Sharpie marker and blacked out the numbers so I wouldn't have that alignment problem. You can't own an 8V92 and be hyper anal.

[JIM CHALOUPKA]

Jim, Not only does the belt length have to do with your mystery, but also the diameter of the pulley, and whether the shafts they run on are exactly parallel. The only way for the belts to stay matched in position would be if everything were perfect, which is not very likely. You could change everything over to use a toothed cog belt if you needed, but you don't, so live with it.:rolleyes:

If you are interested in having some fun and something to do, mark the belt with some white marks measured out along its length. Run the engine and you will see them move around in relation to each other.

If you can get hold of a stroboscope / strobotach you will be surprised at what you will see. It would show up movement and or slippage between the belt and the shive.

http://www.contractor-books.com/EX/461830_31.htm ("http://www.contractor-books.com/EX/461830_31.htm")

If you were just joking around.:confused: :D Never mind

[jimblu]

In response to BrianE's Autofrost post, I'm a new member with an 89 Liberty. I converted my drivers air to 134a and performance is reduced, as expected. I get a 28 degree drop across the evaporator, when the coach is 88 degrees inside, it blows 60 degree air out until the coach cools, (which it doesn't on a hot day). and I have to run the roof airs till it cools. Does the Autofrost do any better?

[phorner]

I am by no means an expert, probably not even a good novice, but I think that any air conditioning system that can drop the temperature by 28 degrees is doing very well.

Seems to me that I once heard a technician say that about a 20 degree temperature differential is about all you can expect.

For what its worth that's my 2 cents (and probably worth each penny)...

[BrianE]

Jim,
Also speaking from a proven position of non-expertise, I would agree with Paul that your system seems to be doing a good job. Would also think that changing refrigerants often could possibly cause problems. When Prevost makes the change from R12 to 134a they recommend changing all of the hoses due to incompatibility of the mineral oil lubricant (used in R12 systems) with Ester oil (used in 134a systems). The AC techs that I have spoken to however didn't think this was much of a problem as long as the system is totally evacuated and flushed when changing over. :confused: