Hi Guys

I have a 1999 F150, 4.6 motor, 4x4 , auto
My question is when I accelerate i get this howling sound coming from the engine. I think??
Could this be my clutch fan??

 

Yes it could be. Has it just started or has it always done it?

 

does the sound go away after the truck is warmed up a bit or is it constant the whole time it is driving?

 

Only when you "accelerate" but not when you blip the throttle parked?

I ran a wild goose chase with a shreaking sound whenever the motor speeded up, moving or not. First idea was serpentine belt noise, but new belt changed nothing & old belt looked perfect. Suspecting the fan clutch, I took it off & ran the motor, again it changed nothing. Recommended replacement of belt tensioner & idler pulley also did nothing!

A tip is to spray the belt w/water while running, avoid the temptation to spray w/belt dressing or aerosol lubes which can damage the belt. Water immediately silenced my noise, but only for a few seconds-until it dried. However this confirmed the noise was generated by a belt issue.

I discovered the harmonic balancer had failed, even though I'd also run the motor w/o the belt on & it made no noise. The balancer relies on a rubber ring to precisely align the pulley on it's core. In my case the otherwise perfect looking pulley had spun & moved back toward the front of the motor ~1/8". Enough to cause the no longer inline AC pulley to protest loudly. Note that there was no sign of oil leakage & several veteran mechanics looked at it & missed it. My pulley was rubbing quietly against the motor, resulting in the belt being pulled rearward & out of alignment w/AC pulley, causing belt chirping at idle & wailing as the motor accelerated. Its still hard to believe such a seemingly minor misalignment could make so much noise.

 

Hi guys


It just started, change the belt, also if this helps the noise is always there, even when I am just idling ?????