I have a 2001 Ford Ranger pickup with approximately 72,000 miles and just this past week noticed a really bad squeaking sound coming from the belt area. I took the truck into the shop twice to diagnose the problem. The first time I took the truck into the shop the mechanic put belt dressing on the serpentine belt, but the noise continued. The second time that I took the truck to the shop; the mechanic could not find the source of the problem.
The problem sounds like a loose serpentine belt. The noise can be described as a loud squeaking that increases with higher RPM's. A Google search on this noise turned up null and any thoughts as to the source of this noise would be much appreciated.
What idiot mechanic told you to put belt dressing on a serentine belt? That crap doesn't even work (for long) on V belts. Spend the $20 and change the belt. Then find a new mechanic.
Let me guess: The squeaking happen worst when the motor has been started after sitting for a few hours? It's about the thermister in your alternator, and your failing battery!
As the battery ages it gets minor internal shorts. So maybe a fifth of the power stored in your battery can be lost while the truck is parked. What remains is enough to crank even a cold engine. After cranking, the voltage is down enough tenths of a volt that plenty of current can flow from the alternator to the battery.
How much current an alternator produces depends on how much current is flowing through it's field. The amount of current an alternator can tolerate producing continually is a lot less than it can tolerate producing for a short while. A thermistor can be used to limit how much current the alternator produces after it becomes hot.
A battery that has been parked for a while can demand a lot of current after cranking the engine, and a cold alternator can produce a lot. This puts an increased mechanical load on the pulley. It slips, and you hear it.
Try bringing your belt in the house, and washing it in the sink with whatever you use for dishes. While it dries, clean all of your pulleys with a clean rag and rubbing alcohol. If you like belt dressing, apply it to the belt while it is off of the vehicle, and let the dressing fully dry before you put the belt back on. The old belt mates to the sheaves better than a new one, a new belt might not help.
While the belt is off, check your idler bearing and water pump bearing.
If other things have you thinking about a new battery, get it now. Good luck with your alternator pulley noise.
Excellent response Bill. I fully agree with him and have this issue on my truck, and everytime all I have to do is clean the pulleys, heck you dont even have to remove it. Take it to the car wash, and clean the front of the engine from different angles while the engine is running.. Yes you are goin to get wet, but you have to wash the truck anyway. Once the belt and pulleys are dry it should stop squeaking, but be warned, you might still have to take the belt off to clean up that damn belt dressing if it doesnt come off in the carwash.
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