Belt Squeal

gsl2007 · December 18, 2007

I have a 95 K3500 7.4L. I have replaced the idler pulley, tensioner, belt 2 times and the belt still squeals. I have checked the alternator (replaced 1 year ago and spins free) new AC compressor. Water pump seems to spin free as does the power steering pump. I know the squeal is coming from the water pump pulley because if I lub the back of the belt the noise goes away for a short period of time. I have manually applied more tension to the belt and the noise gets better but is still there. I am at a complete loss. The belt on there now is a Dayco belt which is thicker than the NAPA belt that was on there. The problem just started about 1 week ago. Any help is appreciated.

kgrigsby · December 18, 2007

Hi, I just had the exact same thing happen to my 1999 gmc 4.8l . It looks like you have done a lot of troubleshooting, You have an alignment problem with the serpentine belt. CHECK! the alignment of the belt on all of the pulleys very carefully! My power steering pump pulley was pushed on .035" to far in and had all the symptoms you have described, lined pulley up, squeal gone! you could just barely see the missalignent on the power steering pump pulley and alternator pulley, I would not have believed it either.

gsl2007 · December 19, 2007

Took the front on the engine back apart today. Checked the alignment of the pulleys. All are very good. Checked the end play in the crankshaft, N/P. Did however find the harmonic belt pulley seems to be worn. This is the only thing that looks bad. Ordered a new pulley and a GM belt. Should be in tomorrow. I hope this fixes the problem.

Wingnut · December 19, 2007

You sure it's the belt squealing?

Every time I've had a problem with anything related to belt noise on these trucks...It's been the bearings in one of the pullies.

gsl2007 · December 20, 2007

No question it's the belt.

Today I received the new parts. First off the AC Delco belt is different than the parts stores. The ribs are broader and rounded over. This makes it fit tighter in the grooves. I installed the new pulley and rechecked the alignment to the power steering pulley this time with a straight edge instead of by eye. I did find it was .100 out of position. I installed washers behind the bracket to make it in alignment. I reassembled everything and so far so good.

Thanks Northern rider for the heads up I think the problem was the alignment. I also think the factory belt is better than parts store replacement belts.

kgrigsby · December 20, 2007

No question it's the belt.

Today I received the new parts. First off the AC Delco belt is different than the parts stores. The ribs are broader and rounded over. This makes it fit tighter in the grooves. I installed the new pulley and rechecked the alignment to the power steering pulley this time with a straight edge instead of by eye. I did find it was .100 out of position. I installed washers behind the bracket to make it in alignment. I reassembled everything and so far so good.

Thanks Northern rider for the heads up I think the problem was the alignment. I also think the factory belt is better than parts store replacement belts.

Hi glad to help, I think you are right about the belt also, the factory belt i have has over 240,000 km and still looks like new, no cracks, etc, according to GM it is actually a lifetime item. I always try to buy GM, AC Delco if I need parts as long as they are priced reasonably, and quite often they are cheaper.