90 k1500 underhood squeal...

Messages
233
Location
Minnesota
1990 Chevy K1500 4x4 pickup, 5.7L auto, with 21k miles. Recently got dad's old baby back to running (it was parked a few years with what I assumed and turned out to be a bad fuel pump that I didn't have the time or physical ability to change) and was running good at first... all the sudden now there's an underhood squeal. It kind of started out of nowhere after an oil change after running fine at first (wasnt present upon first start). Sigh. https://youtu.be/SpfV8N1BLVQ It's hard to 100% localize at first it sounded like it's on the left side, now it seemed right, so as of this moment i'm wondering if it's the AC compressor. Which is a bit lame as it's winter and it's been out of freon for 5 years so I thought it'd just freewheel... unless it's some idler dying or... something? It's clearly not engaged yet the squeal seems close to there. (although the video doesn't tell it as well) I have to try and check to find what SPECIFICALLY is squealing to avoid playing parts cannon but i'm not sure what to do as i'm not a mechanic just a tinkerer... like to see if it is or isnt the AC compressor, my wallet cant take any more abuse of paying someone else to fix anything (credit cards are near maxed and paying interest only until february school loan is deposited) and i'm not up for any more heavy work anything in the winter - i'm wondering if I could just bypass it entirely with a shorter serpentine belt as if it's not even there, if that could be done easy instead of hard. At least until spring or something when messing with it isn't cold misery. I suppose it's possible I got something on the belt inadvertently (I was doing an oil change but was pretty careful/pretty sure nothing got near the belts, the wind was from the other way and I used a funnel) but I didn't hear the noise at first, unless someone can suggest that'd clean oil from a belt without causing a problem in case that's what I did. I could also just drive it a bit and see if it goes away... it seems strange to me a mechanical part would fail with so few miles so I should probably rule out the more obvious first.
 
Messages
2,840
Location
Americus, GA
An old trick that works is to cut you a piece of hose. Stick on end to your ear and move the other end around to the suspected areas. Be careful where you put the hose. Don't put it around the spinning ends of your accessories.
 
Messages
11,004
Location
Cincinnati, OH, USA
I've had AC compressor clutches make that noise, could be an alternator bearing (but that doesn't sound like one). Try spraying just a little WD-40, not enough to soak the serpentine belt, in that AC compressor clutch-see if the noise goes away (or gets quieter). Otherwise, (as above) a mechanic's stethoscope, or even listening to the end of a long screwdriver, should tell you which it is.
 

Bud_One

Site Donor 2021
Messages
2,124
Location
Spring,Texas
Originally Posted by MParr
An old trick that works is to cut you a piece of hose. Stick on end to your ear and move the other end around to the suspected areas. Be careful where you put the hose. Don't put it around the spinning ends of your accessories.
Or a really long screw driver
 
Messages
4,161
Location
Texas
Originally Posted by Snagglefoot
One thing you can do is remove the fan belt and rotate each pulley by hand to check for any rubbing noise or tightness.
Good advice . As long as you do not run it very long , you can even start it . Squeaky pulley is not uncommon . Does the belt look like it needs replacing ? The A/C compressor should have a bearing that the pulley turns on , when the A/C clutch is not energized . I have had to replace one on a GM A/C compressor when it started making noise . Harbor Freight sells this to help trace down noises . Works OK , but be careful not to get the end into the belt . https://www.harborfreight.com/mechanics-stethoscope-63691.html Check the water pump , alternator , Compressor , idlers , etc. for noise . For what it is worth , on something like an alternator , you can even tell if the front or back bearing is noisy .
 
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