Alternator Belt Squeal on a 460

[Pet9782]

Hi all I'm new here but not new to this vehicle. (Sorry for the long post I just want to supply you with all the details)


We have a 94 E350 15 pass. with the 460 that has 28K on it. We really only use it to tow the camper and move people to and from the Airport. We have owned the van since it had 2K on it and 6 Months old. Ford used this van in Detroit to move execs. around.


Lately we have been having an alternator problem with it. When we start it the belt(s) (I believe only the air pump/ alternator) would squeal and the alternator would discharge slightly, it would stop and be fine. It would do the same thing if the rear fan was on at a stop but never when cruising. A few weeks ago the alternator called it quits so I took it out and had ours rebuilt. They fully tested it and replaced the voltage regulator.

I put it back in let it run in the yard with the A/C on and both blowers on high. No squeal and the gauge stayed around 3/4. The next day I test-drove it to work and the first thing I got was a squeal and low voltage. I changed out the belt with a spare that we had for it. That work fine for a few weeks, but the gauge would drop to about the 1/2 mark at idle with both blowers on high, never any squeal. (Voltmeter would read 13volts in that condition). Now the squeal is back when you first start it or when there is a heavy load.

Is the 130amp alternator sensitive to belts? Did they miss something on the rebuild? Or is there some sort of electrical problem someplace in the truck?


Again very sorry for the long post

Pete

[taz4x4150]

Is this 1 serpintine belt that drives everything, or more than 1? The first thing I would suggest is a new belt tensioner. You replaced the alternator and belt, but it's the tensioner that will keep it from slipping under a load.

[BroncoJoe19]

See if you can better localize where the squeel is coming from. Sometimes using a cut off piece of garden hose is a good aid to listen with. Sometimes a cardboard tube (like from gift wrapping paper) is helpful. Otherwise a long screwdriver held to your ear, or better yet a mechanic's stethoscope. Just remember that whenever you stick your head inside a running engine compartment, that you are not wearing any loose clothing or jewelry that can get caught.

Those smog pumps have a tendancy to sieze.

Could also be that when they replaced the regulator in the alternator they should have replaced the bearings, and didn't.

[theoldwizard]

BTW, dashboard gauges are fairly inaccurate. If you really want to know what is going on with your charging system buy a digital volt meter. You can get a decent one for under $30 at Sears.

[Pet9782]

Is this 1 serpintine belt that drives everything, or more than 1? The first thing I would suggest is a new belt tensioner. You replaced the alternator and belt, but it's the tensioner that will keep it from slipping under a load.

This engine has 2 belts. One that does the A/C and Power Steering, this one has the spring loaded belt tensioner.

The second belt does the alternator and Air Pump, this one is tightened by the alternator. (the one that is slipping)

See if you can better localize where the squeel is coming from. Sometimes using a cut off piece of garden hose is a good aid to listen with. Sometimes a cardboard tube (like from gift wrapping paper) is helpful. Otherwise a long screwdriver held to your ear, or better yet a mechanic's stethoscope. Just remember that whenever you stick your head inside a running engine compartment, that you are not wearing any loose clothing or jewelry that can get caught.

Those smog pumps have a tendancy to sieze.

Could also be that when they replaced the regulator in the alternator they should have replaced the bearings, and didn't.

I have a good feeling that the belt is slipping on the alternator because the pulley looks shiny (from slipping) and the holes in the alternator had rubber sucked into them from the internal cooling fan.

When I get a chance to tear it down again I will check into the air pump.

Would a bad bearing cause it to slip only under a load? If that is the case they will get it back they gave me a warranty, and the place that did it is a good friend of a friend I have used them a lot.

BTW, dashboard gauges are fairly inaccurate. If you really want to know what is going on with your charging system buy a digital volt meter. You can get a decent one for under $30 at Sears.

I did get those voltage reading from a multimeter at the battery.


Thanks for all the help, I will keep you posted.