Howling sound from 99 Suburban

**bferland** · 10-17-2008, 08:46 PM

We have a 99 Suburban 2500 with a 454. Recently we have heard a "howling" noise coming from under the hood. I can only describe it as a high piched howl, if that makes any sense at all! It has no rime or reason but it speeds up and slows down with the truck, so I am leaning twards the pulley system or possibly the alternator? The brakes are fine, I think. Stopping is no problem. I have owned Chevey's all of my life and never heard a noise like that. There is no changes in the gauges when it happens and it doesn't make the noise all of the time. Any suggestions will definately help!!

**MrShorty** · 10-17-2008, 11:31 PM

Does it make the noise at idle? When you say, "the noise speeds up and slows down with the truck" do you mean that it follows engine speed or vehicle speed?

One "howl" that is normal and comes and goes is the fan. When the fan clutch warms up, it engages the fan and it howls. Sometimes when it's extra cold, the fan will be engaged until the fluid in the clutch gets warmed up a little bit. Depending on what the weather has been doing lately, the howl might be the fan.

If it makes the noise at an idle, you might use a stethoscope and poke around at the pulleys and bearings associated with the serpentine belt. Be careful not to get anything (hair, shirt, fingers, arms, etc) wrapped up in the belt.

See if you can narrow down where the noise is coming from.

**95CTburb19** · 10-19-2008, 02:56 AM

My sierra spent most of its life in GA and doesn't like the cold very much. The fan makes a ton of noise when I first start it in the winter time and continues to be loud until it warms up. If that isn't your problem then I think checking the alternator and the other belt driven components could give you some idea of whats going on.

**bferland** · 10-21-2008, 10:34 AM

Well thank you very much for your help!! We have narrowed it down to the alternator or the fan clutch.. It hasn't done it in a few days and the truck is running great as always, but it has been warmer here in AZ. The battery gauge is great as well so I see no catastrope's in the future!! Thank you again!!