Alternator squeal

wanab5150 · #1 (**permalink**) 04-10-2011, 09:32 PM

I have a Roush 427 in my Superformance. When the car was new, I had to trade out the serpentine wide belt for a grooved belt because I added a vacuum pump. Ever since (9000 miles now) when I turn on the lights or the fans come on the alternator has squealed at low RPM right after starting.

Today for no apparent reason it started screeching from start up and through a 20 mile drive and would not stop except at idle. At idle it showed pulling a few Amps but as soon as I accelerated the amps dropped to zero and the screeching started.

The belt is tight and I have kept it tight but no matter how tight I get it, it will still make noise at start up with the lights or the fans on before today.
The pulley has some grooves in it on one side, and it appears that the belt is primarily running on the edges and it looks like the edges actually made the grooves in the pulley. The belt sides (other than the edges) look like they don’t even contact.

It’s not about tension….and the alternator was tested and it did not squeal under load at the shop on the bench. Also, the belt is only about 200 miles old. The water pump has 9000 miles on it and it turns free and not leaking. And, you can hear that the squealing is coming from the alternator anyway.

My quandary is more about the pulley size. It’s a 2 3/8” O.D. Does that sound like a normal size. It was put on when the pulleys were traded out for the “v” belt pulleys. How can you tell if it's a standard pulley?

Clayboy · #2 (**permalink**) 04-10-2011, 10:00 PM

Tom,
I'm not trying to be a smart a$$ (OK, maybe I am) but have you thought of starting a thread entitled, "What else could go wrong with my car?" or "Bitten by the snake, every time I turn around my cobra bites me in the wallet".

Good luck with this one.
Bob

cobraman428 · #3 (**permalink**) 04-10-2011, 10:05 PM

Even though the belt is tight, you've "cooked" the belt and hardened it & it needs to be replaced. Make sure the correct width belt comes in full contact with the pulley. A slightly loose belt will generate alot of heat and in no time harden the belt.

menace1 · #4 (**permalink**) 04-10-2011, 11:58 PM

A bad alternator will squeal like a pig when the worn bearings get hot. Looks like it's time to part with more dunero. Like Bob said, these cars are made to bite you in the wallet and other places..

PANAVIA · #5 (**permalink**) 04-11-2011, 02:01 AM

If it was from Roush - the alternator should be a powermaster unit.

it can be serviced and rebuilt at a local alternator shop.

a reason for the bearings going may be an alternator to pulley alignment issue.

if the alternator main shaft is not parallel with the cam and crank shafts mean lines, excessive alternator ( and water pump ) bearing wear can result.

I would take your alternator to a rebuild shop in the area and ask them to check it out.

---Steve

mreid · #6 (**permalink**) 04-11-2011, 06:55 AM

In addition to the above (I also agree that the belt has become glazed), make sure you have the correct width belt for the pulleys. Also, 2 3/8" is a very common pulley size.

wanab5150 · #7 (**permalink**) 04-12-2011, 11:35 AM

Problem solved: it seems that everyone who answered was correct in one way or another. Clayboy, yes "bit me in the azz again!" would work as a thread title!.

First, matching the belt to the alternator pulley revealed that the belt was too narrow to make complete contact within the pulley. This was the belt installed when I had the pulleys changed out by the installer. I'm sure this had nothing to do with the alternator failing.

Second, even with the new belt the alternator started screaming after a few minutes and was not putting out amps. Apparently, it works for a few minutes and them something goes wrong inside.

A new $170 Powermaster 100 amp alternator cured the problem and the new wider belt seems to have cured the slipping when the lights and fans are on like it has done from the beginning.

I considered a lower amp alternator but I was told by the shop that tested it that the MSD ignition draws 20 amps? That with the twin fans and the lights and maybe the heater pretty much requires the 100 amp version. I'll have the burnt one rebuilt and shelf it just in case.

thanks for the help everyone......

Z-linkCobra · #8 (**permalink**) 04-12-2011, 12:31 PM

Make sure you take a good look at your alt. pulley. When you get something like that going on it will also glaze the pulley or polish it if you will. It would hurt to take the belt off and take some sand paper folded up to the grooves on the pulley.

You dont want it rough to the point of tearing up the belt....just not baby bottom smooth and shiny either.

Just a thought.

Gene