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Dads72 · 07-10-2003, 10:21 PM

Idle is fine.
Rev it up in park and it shreeks - like a bad bearing someplace.
Think it is either the water pump, the fan clutch, or the alternator.
Before I start throwing parts at it, is there a way to isolate the source of the problem?
If it helps, it only seems to do this when I rev up the engine and then back off of the throttle.
I get the bad sound when I back off.
Thanks

70c10 · 07-10-2003, 10:24 PM

Check the tension on your belts. BTW- I'm definitely not an engine guru!,lol

Dads72 · 07-10-2003, 10:28 PM

Check for too loose, or too tight?

1971 Cheyenne · 07-10-2003, 10:46 PM

Make sure they have pretty good tension on them. whenever I tighten them, I make it so you can grab the belt in the middle of the two pulleys and move it back and forth about an inch with just a little bit of effort. The squealing is usually the belt slipping and if thats the case it just needs a little bit of tightening.

70shortnphat · 07-10-2003, 11:01 PM

If playing with belt tension does'nt help then start removing belts one at a time running the engine in between and try to make the noise. If you remove a belt and the the noise stops you can narrow down your search or isolate the problem.

GasHog396 · 07-11-2003, 04:49 PM

As you loosen and check each belt, also turn the associated accessory(ies) by hand to make sure they spin freely. I had a similar problem with my p/u and it turned out to be the water pump on my 396 actually starting to seize up. The revs at idle weren't sufficient to cause the belt to slip, but just touch the gas and it sounded like someone was trying to give a cat a bath under there, only louder. I could hardly turn the thing over by hand and the pump never leaked a bit of coolant. Also check the condition of the belts. Slipping will leave a slick glossy look on the belt(s) as will age. Time to replace them if that happens.

tom hand · 07-11-2003, 04:59 PM

You can use WD-40 to isolate belt sweaks...just try it on one belt at a time till you find the culprit. Then tighten/replace as necessary.

jon engel · 07-11-2003, 08:45 PM

An old trick is take a long screw driver and hold the end on the part that you want to check,hold the handle with your thumb over the end then put your ear on your thumb and listen for grinding or squealing sound. This method works in most every case. You can also do this to find the side of your engine has noisy lifters and if you have bearing problems

Class of 69 · 07-11-2003, 08:56 PM

Getting the squeal on decell, indicates belt problems. You've already heard...look for aged (cracked or glazed) belts, and replace, or loose tension. I would personally change out a belt that was loose enough to squeal, as it will have gazed from slipping anyway. One last tip...run some emery cloth on the pulley groove too, to break the glaze on it from slipping. Gives a new belt a better chance to "seat" in.

07-10-2003, 10:21 PM	#1
Dads72 Registered User Join Date: Nov 2002 Posts: 427	Engine gurus Idle is fine. Rev it up in park and it shreeks - like a bad bearing someplace. Think it is either the water pump, the fan clutch, or the alternator. Before I start throwing parts at it, is there a way to isolate the source of the problem? If it helps, it only seems to do this when I rev up the engine and then back off of the throttle. I get the bad sound when I back off. Thanks

07-10-2003, 10:24 PM	#2
70c10 67-72 Addict! Join Date: Feb 2002 Location: The TAX State! Posts: 7,856	Check the tension on your belts. BTW- I'm definitely not an engine guru!,lol __________________ Jim 1970 C/10 Fleetside w/Ghost Flames Lowered 4.5" front and 4" rear (Raked) 355/350 Turbo w/shift kit 10" Redneck Performance Verter w/2500 stall Hooker Super Comps part#2808-1 Performer RPM Air-Gap 12 Bolt w/3:73 gears- Eaton Posi Comp Cams XE262 with 1.6 Crane Energizers, Road Demon 625 and Brodix IK 180 heads

07-10-2003, 10:46 PM	#4
1971 Cheyenne Registered User Join Date: Nov 2002 Location: Bellevue, WA Posts: 1,480	Make sure they have pretty good tension on them. whenever I tighten them, I make it so you can grab the belt in the middle of the two pulleys and move it back and forth about an inch with just a little bit of effort. The squealing is usually the belt slipping and if thats the case it just needs a little bit of tightening. __________________ Brian Pal 1971 Cheyenne 10 454/th400-Undergoing a full frame off resto. 1972 Chevy short/step 2wd, 350/th350 1983 M1009 CUCV Military K5 Blazer 1981 Dodge 1 ton 4x4 dually flatbed

07-10-2003, 11:01 PM	#5
70shortnphat "See the U.S.A....." Join Date: Apr 2002 Location: Richmond TX. Posts: 269	If playing with belt tension does'nt help then start removing belts one at a time running the engine in between and try to make the noise. If you remove a belt and the the noise stops you can narrow down your search or isolate the problem. __________________ 1970 short bed fleetside 1949 all origional chevy 3600 1974 camaro Richmond , Texas(just S.W.of Houston)

07-11-2003, 04:59 PM	#7
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	You can use WD-40 to isolate belt sweaks...just try it on one belt at a time till you find the culprit. Then tighten/replace as necessary. __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

07-10-2003, 10:28 PM	#3
Dads72 Registered User Join Date: Nov 2002 Posts: 427	Check for too loose, or too tight?

07-11-2003, 04:49 PM	#6
GasHog396 Registered User Join Date: Jun 2003 Location: Ponder, TX Posts: 33	As you loosen and check each belt, also turn the associated accessory(ies) by hand to make sure they spin freely. I had a similar problem with my p/u and it turned out to be the water pump on my 396 actually starting to seize up. The revs at idle weren't sufficient to cause the belt to slip, but just touch the gas and it sounded like someone was trying to give a cat a bath under there, only louder. I could hardly turn the thing over by hand and the pump never leaked a bit of coolant. Also check the condition of the belts. Slipping will leave a slick glossy look on the belt(s) as will age. Time to replace them if that happens.

07-11-2003, 08:45 PM	#8
jon engel Registered User Join Date: Jun 2003 Location: Punta Gorda,Fl Posts: 3	An old trick is take a long screw driver and hold the end on the part that you want to check,hold the handle with your thumb over the end then put your ear on your thumb and listen for grinding or squealing sound. This method works in most every case. You can also do this to find the side of your engine has noisy lifters and if you have bearing problems __________________ Jhook

07-11-2003, 08:56 PM	#9
Class of 69 Registered User Join Date: Mar 2003 Location: Stillwater MN Posts: 1,166	Getting the squeal on decell, indicates belt problems. You've already heard...look for aged (cracked or glazed) belts, and replace, or loose tension. I would personally change out a belt that was loose enough to squeal, as it will have gazed from slipping anyway. One last tip...run some emery cloth on the pulley groove too, to break the glaze on it from slipping. Gives a new belt a better chance to "seat" in. __________________ 69 GMC K10 ..some restoration required....still..



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