1994 GMC C1500 - Serpentine Belt Oddity

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#1
Make
GMC
Model
C1500
Year
1994
Miles
150K
Engine
350
Serpentine belt came apart on the highway. Parked it. Went to auto parts store and purchased new belt. Drove truck home. The new belt came apart a day later. Figured out the steering pump was going bad. Put another new belt on, had truck towed to shop and had a new pump, HP hose and tensioner pulley installed. Now the new belt I bought will not fit. It sits outside of the idler pulley, instead of going around it on the inside. I've checked and rechecked the part number, and cannot find anything wrong. 1994 GMC C1500 with 350 engine, without air pump, with A/C. Dayco part is 5060995. I'm assuming either the new pump pulley or the new tensioner pulley is a different size? Look at the attached photo and give me an idea of what size belt I should try. The 506995 is 95.5 inches long.
 

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#2
Short answer....you gonna need a longer belt.

Might check with the shop to see if they have the old parts for comparison.
Are you sure the tensioner arm is allowing adequate movement to install current belt in proper path? 1555425114707.png
 
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#3
Short answer....you gonna need a longer belt.

Might check with the shop to see if they have the old parts for comparison.
Are you sure the tensioner arm is allowing adequate movement to install current belt in proper path?
Dan: The shop installed a new pulley on the tensioner. Can the arm be adjusted or does it only go on one way? How would I determine if the arm is not moving through its full path?
 

billr

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#5
I see two likely possibilities here. There are a lot of different belt lengths for the specific vehicle, mostly depending on the alternator (max amperage) fitted; you may just have the wrong belt. Also, aftermarket idlers and tensioners seem to not always stick to the OEM pulley size; maybe trying to make "one size fits all" to reduce price of the part they sell. What they don't tell you is that you will have to determine the size for a new belt and buy that too. Yeah, compare old parts to new. If the shop had to route that belt contrary to the standard config, I would expect they would also have kept the old parts to be ready to explain why that was necessary.
 
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#6
Well, the rotation (degrees) on the tensioner seems right. The tensioner pulley is 3.5 inches in diameter. I tried again today to make the existing belt work, just no way. I'm going to start looking at different belts to try to find one about 1 inch longer. Is it okay to drive it like this?
 
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#7
What if I change out the pulley to a smaller diameter? Either the tensioner pulley or the idler pulley. I'm seeing some with the same bearing size that are and inch smaller in diameter than what is on my truck.
 

billr

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#9
What alternator do you have? Were you able to look at the old parts?

You should be OK driving with the wrong belt routing shown in the picture, but the belt may slip on the A/C pulley when A/C is working hard. If you hear any hint of a belt squeal when A/C is on... turn it off. You don't want to have the belt fail and then lose coolant circulation.

PS: I am assuming the belt tension is still adequate, the tensioner hasn't run out of travel with the belt length that is only there now
 
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#10
What alternator do you have? Were you able to look at the old parts?

You should be OK driving with the wrong belt routing shown in the picture, but the belt may slip on the A/C pulley when A/C is working hard. If you hear any hint of a belt squeal when A/C is on... turn it off. You don't want to have the belt fail and then lose coolant circulation.

PS: I am assuming the belt tension is still adequate, the tensioner hasn't run out of travel with the belt length that is only there now
Shop does not have the old parts. I have the first belt that shredded. I'm going to try to measure it tomorrow, if there is enough of it left. The AC does not work on this truck, so I never turn it on.
 
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#11
If AC pulley is not going to "do any work", then belt routing as shown should work fine. Bill's concern about adequate belt tension should still be addressed...if you put a wrench on the tensioner (with belt installed) and find that you can move it "in the direction that makes the belt tighter, not looser", then you will know that the tensioner is operating within it's proper range of travel.