O.T. Squealing Noise under the Hood

I realize this isn't a tractor problem but I know there are some very knowledgable individuals on this "Board". Recently I have heard a squealing noise under the hood of my 2004 GMC pickup.I checked with the dealer and the mechanic thought the alternator bearing is failing. Cost to replace is a little over $300. The place that works on my tractor generators said they would repair it for alot less money but won't remove it from the vehicle. How do I take it out especially getting the belt off and back on? I am not a mechanic. HELP!!!

First disconnect the battery ground. Then remove the wires from the alt. Take a picture or make a drawing of where the wires were.
Just remove the bolts for the alternator. Getting the belt off is a snap now. Getting it on is the trick.
When you have the rebuil alt in hand, bolt it back in. Follow the serpentine belt around, you should find a backside idler. That's a spring loaded flwt pulley that tensions up the belt.
Get the belt on all of the pulleys except the alt, then use a pry bar to take the tension off the idler and slip the belt over the alt pulley.

Might need a friend, sometimes you almost run out of hands.

Gordo

could also be the bearings in the idler pulley and or tensioning pulley are going out instead of the alt bearings. with the engine idling, listen around and see if you can locate the source, then turn on all your accessiroies, lights, heater on high, winshield wipers, rear defog ect to get a big current draw, then listen again to try and isolate it. if it is the idler or tension pulley napa had them. many of the idler pulleys have left hand thread, so keep that in mind when dis-assembling.

Another one that can squeal is the bearing in the A/C compressor. Try switching your A/C off and on to see if that makes any difference. Keep in mind that your defroster mode uses the compressor, too.

Other than that, the others have it pretty well covered.

If the mechanic only "thought" it was the alternator bearing, it doesn't sound like much of an inspection. Then if that don't fix it, it will only be another 1500 bucks for the a/c. Unless you have your stethoscope handy, you will have to improvise. Get a long, preferrably hollow, small diameter tube/pipe or I've used a wratchet extension in a pinch. Without getting it caught in the fan or the belt, put one end on the non moving shaft of the bearing you want to check and put your ear to the other end and listen. The bad bearing will be magnified and obvious.

The stethoscope or a home made one also works good for checking valves, water pumps, and isolating other noises on the engine.

The diagram for the belt will be on a label under the hood somewhere.

Don't know about yours, but some alternator removals require removal of shrouds, the a/c, other belts, air cleaners, and you name it, and sometimes from the top or underneath. Sometimes takes special tools and pencil length fingers and pencil thin fingers, and paper thin hands to get at certain bolts and the alternator. Murphys rule is that the bolts will be harder to get off than they were put on. May need a breaker bar or cheater pipe. Probably need a swivel socket to get on one and then there will only be room for a half inch of wrench/wratchet travel so it will take a half hour to remove or loosen a bolt. The wire quick connectors will be stuck and likely pull a wire loose or break the connector getting it apart. You can never find the tab on the wire connector and figure out if you squeeze it or lift up on the tab to pull them apart. It will probably take you 3 or 4 times longer than the gm mechanic.

Then you may find out that the belt was a little loose and just needed tightening or maybe a little belt spray on it. Give the squeeky bearing a few shots of spray silicone on both sides to see if it helps it temporarily.

Good luck. Let us know how it goes.

Usually the bolt that holds the idler on can be used to take the tension off the belt. Put a ratchet wrench on it and lean on it a little.

If you figure it is the alternator bearing Do not purchase one from an auto parts store. it is WAY cheaper to go to a starter/alternator rebuilder and have them replace the $5 bearing. I just went thru this on my '98 GMC CarQuest store and Napa both wanted $145+ for a reman and $190+ for a new alterator. Went to my local rebuilder and removed, rebuilt, and replaced for $50 They replaced the bad bearing and some other piece known for wearing out. I use this rebuilder for all tractor gennys, starters, and alternators. Just my thought.
Brad

Best thing is to loosen the belt ---then spin each "accessory"---water pump, alternator, pulley on A/C, power steering-- everything. See which one is at fault.

You may be able to isolate the offender by taking a metal rod and place one end near the alternator bearing (motor running)and place the other end close to your ear. Also, try near the bearings of other items as suggested- ie -idler pulley, AC pulley etc. Hope this helps.

Are you sure it isn't belt squeal? As belts get old and hard, they squeal. Test by squirting some water on the belt while running. If it quits, replace the belt. BTW, the water will keep it quiet for maybe 5 minutes. Rinse out the wife's dish soap bottle, fill with water and squirt away. Keep your valuable body parts away from the belt and sheaves.