WaterH
Well-known member
So I have had multiple belt related problems on my Cummins 4BT and the latest is really weird.
First a little backround. I’ve had several different belt routings, but I will only talk about the last two.
The original (somewhat successful) belt setup was crank, idler, alternator, AC compressor, tensioner and back to the crank. This set up lasted a long time. I had the mounts to the idler break twice over a long period of time. I ended up making a new mount that was bullet proof. That lasted for awhile and then the idler itself started making noise. When I was making that mount, someone on here mentioned that I didn’t need that idler at all. When it started making noise, I got a shorter belt and bypassed it.
I started hearing a belt noise and a clicking noise. I figured I needed a new water pump, but for whatever reason I threw a new belt on it and the noise was gone. The old belt was not very old and I couldn’t see any problem with it. But the noise was gone, so I just threw the belt in a box for a spare and went on my happy way.
A couple days ago, I start hearing a belt noise again. This time it sounded like a bearing squeal and there was no clicking. I really thought it was the water pump, but because of last time, I decided to buy a new belt and try it. Lo and behold, the sound is gone.
I really want to understand this. I have three belts that are not very old and two of them make noise.
First thing I did is try to measure them for belt stretch.
This pic is not very clear, but the new belt compared to the oldest does appear to be shorter. I devised a better way to measure them. Oldest belt.
New belt.
Maybe a 1/4” different. I don’t have a pic, but the belt I just took off did not appear to be stretched. My first conclusion is the oldest belt was stretched so much that the tensioner was hitting its stop making the clicking noise. That solves that mystery, but why is belt number two making this squeal noise?
I looked close at the belt and the only thing I can see is some shinny spots in the grooves.
I know the pic is not great, but they aren’t real apparent. I took a pic and raked it in the groove and the shinny spots kind of hang up the pic, but don’t really come out. They almost appear to be part of the belt fiber. Anybody got any knowledge on this?
First a little backround. I’ve had several different belt routings, but I will only talk about the last two.
The original (somewhat successful) belt setup was crank, idler, alternator, AC compressor, tensioner and back to the crank. This set up lasted a long time. I had the mounts to the idler break twice over a long period of time. I ended up making a new mount that was bullet proof. That lasted for awhile and then the idler itself started making noise. When I was making that mount, someone on here mentioned that I didn’t need that idler at all. When it started making noise, I got a shorter belt and bypassed it.
I started hearing a belt noise and a clicking noise. I figured I needed a new water pump, but for whatever reason I threw a new belt on it and the noise was gone. The old belt was not very old and I couldn’t see any problem with it. But the noise was gone, so I just threw the belt in a box for a spare and went on my happy way.
A couple days ago, I start hearing a belt noise again. This time it sounded like a bearing squeal and there was no clicking. I really thought it was the water pump, but because of last time, I decided to buy a new belt and try it. Lo and behold, the sound is gone.
I really want to understand this. I have three belts that are not very old and two of them make noise.
First thing I did is try to measure them for belt stretch.
This pic is not very clear, but the new belt compared to the oldest does appear to be shorter. I devised a better way to measure them. Oldest belt.
New belt.
Maybe a 1/4” different. I don’t have a pic, but the belt I just took off did not appear to be stretched. My first conclusion is the oldest belt was stretched so much that the tensioner was hitting its stop making the clicking noise. That solves that mystery, but why is belt number two making this squeal noise?
I looked close at the belt and the only thing I can see is some shinny spots in the grooves.
I know the pic is not great, but they aren’t real apparent. I took a pic and raked it in the groove and the shinny spots kind of hang up the pic, but don’t really come out. They almost appear to be part of the belt fiber. Anybody got any knowledge on this?
