I just purchased a 1997 F-150 XLT 4X4 with 62450miles, 4.6L with auto transmission. The problem I am expierencing is a whisting sound that seems to be coming from the air vent when the truck is stopped in gear. (it sounds like the wind whistling in the winter) I am wondering if anybody else expierenced this problem and what the fix was or if it's just a normal sound for the amount of miles on it.
When the vehicle is in PARK or NEUTRAL, the engine idles at about 900rpm and the whistle is really faint. When I press the brake and put it in gear I notice that the engine drops to about 800rpm and the whistle is more audible. I tried driving at idle speed in an empty parking lot with the fan on and then off but the sound is still there. The sound disappears between 1000-1200rpm range. The only modification I have tried so far was to change out the stock air filter with a K&N and the sound is still there.
I took the truck to the dealership since I am still under my 3 month/3000 mile powertrain warranty and the technician said that the sound was definately from the engine bay and said that it was the alternator going bad. He explained it as more current is drawn, the alternator starts to work harder to charge the battery and that's where the sound is coming from. He said that 97 F-150s had problems with the alternator bearings going bad and that the whistling was the bearings starting to go. Said that the alternator will start to make more of a clunking noise as the bearings start to go downhill.
Any information on this problem is greatly appreciated!

Thanks,
Chris

 

It is a constant sound or a sound that you only hear when the AC compressor comes on???
If its only when the compressor comes on, it could be bearings in your compressor or low freon (R134).

 

Not sure if this is the same whistle I had on my 95 Explorer or not, but I had a K&N filter in the stock filter holder. I started getting a whistle on that engine, and could not diagnose it nor could the shop. Finally I tried putting the stock air filter back in and the whistle when away.

Ended up not being a big deal since I ended up trading in the Explorer for my Screw 2 weeks later anyway.

Good Luck with the fix.

 

My '97 F150 4.6L has had a whistling sound since the 1st day I drove it 6 years ago. Not loud, just there. Years back on this forum I remember people saying that it was normal. It's a little louder when you put it in gear just like you described. By now I don't even notice it.


In your case I would get it checked out regardless.

By the way, you may also get an oily smell sometimes when you first turn on the AC. That's also normal from what I've read on here.

Mark

 

I recently installed a K&N FIPK2 in my 4.6ltr. On one of the steps, they warn agaist a whistling noise from the air bi-pass valve. This is easily remedied by sawing off the nipple at the end of the bi-pass( connecting to the throttle body) and connecting a rubber hose w/ hose clamp.

the noise might have somthing to do with your intake system???

a leak???

 

Well... took the truck back to the dealer for service again. Told them about the whistling noise and they took a listen to it. After about an hour, I was called into the service area because they couldn't duplicate the problem. We took the truck outside since it was a little more quiet and the sound was heard after some cohercing. I was told that the sound was the clutch fan. Nothing to worry about I guess. It's a far cry from what I thought it was but I guess I will just keep an ear to the situation to listen if it gets any worse. Thanks for all the help.

Chris

 

I think, from personal experience, that we expect our trucks to run as well as an airplane. The fact is, every one of these engines are different, with their own unique sound. As long as the trucks start up in the morning and run with strength all day, getting us home in the evening, everything is well.

The rpm's will drop a little when you put the truck in gear, and the tranny does make a faint whistling noise, along with the idle sounds. I, too, have experienced this sound.

Just keep an eye on it and let us know if you find out anything new.

 

Not sure if this is the same sound or problem but often in Hot weather, you will hear a sound similar when the fan clutch goes to 100 %. When the RPM goes up and some air start flowing, the cluth will disengage. If this sound is only present when it's hot (Especially during the day), then it's probably the fan clutch doing it's thing and is normal.

 

I had my clutch fan replaced at 60,000 because it was going out. Might be the same problem.