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post #1 of (permalink) Old 04-16-2002, 09:51 AM
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Help! - \'75 Blazer (350CID) belts keep coming off

OK, I've seen plenty of posts where someone is yelling 'Heeeeeeeeeeeelp' with some problem or other. Now I guess I've reached that point too! I've owned a '75 Blazer with a 350/350 engine/tranny combination for about three years now that ran like a champ for the first 2 1/2 years. Took it on a couple of week long vacations where we covered over 2000 mi each time and drive it as a daily driver. Then all of the sudden it started tossing the belts last fall. Sometimes 2 months between happening, this last time a week and a half. This is the forth time in six months.

I believe it is either the alternator or the power steering pump belt that starts the problem because I left the A/C belt off for awhile through the winter and it still happened. I've aligned the pulleys on both alternator and power steering pump as close as I can see how. I switched to Gates belts which I'm told are the best. I don't see any visible problems with any of the pulleys, although maybe I don't know what to look for that's not so obvious. Can't see anything wobbling at any RPM, at least under no load. Fan clutch seems to work the way it's supposed to.

I think I'm to the point of just starting to replace stuff to see if the problem goes away. But even then, not sure just what to start with - water pump pulley, crankshaft pulley, alternator, power steering pump, etc. I've also had suggestions that it could be the harmonic balancer. I've been told that the small block Chevy has had this problem since it's early days, to the point where there are supposedly aftermarket flat belt replacement set-ups to eliminate the V belts completely. That seems like an extreme solution, but I'm getting to the point of considering something like that!

Anyone else had this kind of trouble?

Footin' it again.
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post #2 of (permalink) Old 04-16-2002, 06:03 PM
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Re: Help! - \'75 Blazer (350CID) belts keep coming off

The only time I had a belt coming off problem was due to a pulley alignment problem. Usually I added some washers behind the harmonic balancer pulley or behind the water pulley to get things to line up. I doubt you have a pulley alignment problem. I'm also wondering if maybe the press fit pulley on the power steering is a problem. I'm also wondering what's up with the alternator pulley and the alternator bearings. I think I would remove the belts from the alternator and power steering pump and turn each of these pulleys by hand to see if there is some sort of play (front to back) or see if the pulleys might be bent or not runnning true.
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post #3 of (permalink) Old 04-17-2002, 12:03 AM
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Re: Help! - \'75 Blazer (350CID) belts keep coming off

mechanics stethoscope. that'll help find where odd noise is coming from. they work so well. definately worht the investment. you can hear each valve open and close on soem engines. they are absolutely amasing for daignosing stuff like this
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post #4 of (permalink) Old 04-21-2002, 10:10 PM
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Re: Help! - \'75 Blazer (350CID) belts keep coming off

Ihad the same problem with a 77 Blazer we did for my son. It was the harmonic balancer. It was out of true and the wobble would cause the belts to get loose. If the pullys are aligned, it must be one running out of true. It easy to find. Just watch the pullys while the engine is running.
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