LB7 Serpentine Issue

[jgarrison]

Hi, long time lurker, first time poster.

Truck - 2004 Silverado LT 3500 6.6 Type 1 105amp alternator 130,000 miles or so

I have an issue that just does not make any sense.

I had a noise coming from one of the idler pullers (this LB7 has two) about two months ago. I ordered a new tensioner puller and two idler pulleys, replaced all three, I did not replace the serpentine as it had only 10,000 miles or so.

A month later the serpentine belt is shredding.

Replaced belt.

New belt shredded.

Replaced belt.

New belt shredded. Compared old tensioner pulley to the new tensioner pulley, the new pulley was about 1mm narrower.

Bought new pulley and replacement belt. Put on new belt.

Drove 100 mile round trip. (98.7)

Parked truck in driveway.

Started truck, backed out of driveway.

Battery indicator came on, message on readout Battery Not Charging.

Pulled back into driveway, popped hood. Belt popped off of power steering pulley. Belt has nicks and tears.

Bought new tensioner assembly and have a new belt.

Replaced tensioner assembly, put on new belt.

Bumped the engine a few times, belt popped off of the power steering pulley.

When I look at the belt routing everything is in line with the exception of the power steering pulley. The belt is in perfect alignment with everything else, but it is half on and half off of the power steering pulley.

the first photo is the proper routing for my LB7.

the second photo is the tensioner, alternator and air-conditioning pulleys.

the third shows the alternator, air-conditioning and power steering pulleys with the belt in alignment but half off the power steering pulley.

3324

3325

3326


I have NOT touched the power steering, how in the heck can it be out of alignment?

[rapidoxidationman]

The obvious answer is usually the right one: Your power steering pulley is coming off and no longer is in the same plane as the rest of the serpentine belt track. It looks cocked in that last pic.

[DmaxMaverick]

Welcome aboard!

The power steering pump pulley is a friction-fit. Meaning, it is only pressed on. It is possible the pulley has walked off the shaft. Very rare, but it happens on occasion. A properly installed pulley will leave no more than a 3/8" gap between the rear edge of the pulley and the pump forward plate. It appears yours is significantly more than that.

At the least, you'll need a new pulley. And possibly a new pump. You can NOT simply just push it back on. The pulley metal is softer than the shaft, so you may get lucky. A specific installation/removal tool is required for R/R. If significant force (with the tool) isn't required to install it, the shaft is likely compromised, and will repeat what you have now if reused.

[jgarrison]

Thank you gentlemen, I will check it out.

Joe

[jgarrison]

After a not so funny series of events I have replaced the power steering pump pulley.

Removal of the ECU housing and upper radiator shroud provides sufficient clearance to use the pump pulley removal tool and the pulley installation tool.

Always, always, always check the install tool for boogered threads. The bolt shaft must insert centered for about 1 and 1/4 inches.

I highly recommend using a 3/8ths by 16 coarse tap and cutting lubricant to chase out the pump shaft threads before trying to install the pulley on the shaft.

I also recommend using an old piece of inner tube on the shaft so that vice grips or channel locks do not scar the pump shaft.

Walking the die in and out gently works well until you are able to walk the die in the shaft with fingers only.

Pressing the pulley into place takes a little bit with hand tools, do NOT use pneumatics.

The tool will bottom out on the lip of the shaft and align the pump pulley perfectly.

Install the serpentine belt before re-installing the upper radiator shroud and ECU housing.

Bump the motor a few times to ensure the belt is properly aligned, if good start the engine and give it a good look-see and if all is right with the world, install the bottom splash guard.

Once I obtain a 3/8ths 16 coarse x 3/4in bolt and wide washer, I will install it (with red thread locker) into the end of the pump shaft to ensure the pulley no longer 'walks across Texas'.

Thanks for the help Gentlemen.

Joe

[oneton]

I just changed out my power steering pump and bought a new pulley as well. My original was damaged in a accident I had about 6 years ago and just threw a used one on just to get the truck back on the road. I bought the Kent Moore pulley remover and installer and I can tell you it was well worth the money. Service manual wants the end of the pulley flush with the end of the shaft with a .010 allowance either way so if it was out of alignment it'd be easy to tell.

[More Power]

Joe,
Thanks for getting back to us. Jim

[hobie34]

My sons truck is slinging belts left and right with the same symptoms. The PS pulley isn't as dislodged as you show but it has slop. The pump is trashed im sure as it leaks like a sieve. the pump shaft I feel is the source of the slop,but only a 16th of an inch at most. I have replaced the tensioner/pulley assembly and 5 belts. nothing else was replaced prior to the belt slinging fit its having.im down to PS pump or ac compressor. going to run a test later to see if the compressor is the problem but need to be closer to home in order to do it, the only belt I have left with me is half chewed up and will only last a few miles. Long winded but thanks for the insight.

[chessy56]

I must've gotten lucky over the past 15 years as my LB7 has never had a PS pump pulley issue and I've done several belts. What I noticed in the photo is that the tensioner is mounted 180 deg opposite of how mine is mounted, with the second idler pulley being about where the tensioner pulley is in the photo. Did the tensioner mounting change between the '01 and '04?

[JasonC]

My PS pump pulley slid off without warning one night. Luckily everything stayed pretty much in place and nothing got chewed up. Also luckily that the truck has a gear driven water pump, so it was no problem to pull off the belt and drive it home being careful to provide plenty stopping distance.

I decided to replace the PS pump and pulley. Unfortunately the pulleys are not available from GM so I put a China one on from O'Reilly. It's been fine for the past 50k.