4.9 whine when accelerating
Thread Starter
|
Senior User
Joined: Oct 2007
Posts: 166
Likes: 0
4.9 whine when accelerating
I have a 1985 F-150 with the 4.9L 300 cu. in. inline six with the C-6 automatic transmission. What has me concerned is when I accelerate I hear a whining or whistle type noise coming from under the hood. It is not an air type noise. I don't hear it at idle, but when it is revved you can hear it. It only does it when the gas pedal is mashed. Let off the gas, it can't be heard. The motor, transmission, a/c compressor, power steering pump and carburetor have all been rebuilt so I'm kinda dumbfounded. I'm thinking it could be one of the accesorries on the engine belt but I am not a mechanic so I don't know. Anyone with knowledge on these older trucks? Replies are GREATLY appreciated, thanks!!
Elder User
Joined: Dec 2005
Posts: 557
Likes: 0
Originally Posted by srercrcr
I have never had the gas pedal to the floor in 24 years, can't help you.
. I would imagine if its only there at WOT that its probably the air rushing sound from the carb opening. I got a little whistle at WOT also. Just sucking air through a small hole at high velocities. I wouldnt worry about it unless it gets IMMENSELY worse. Meaning I.E. always there, louder.
Senior User
Joined: Jun 2004
Posts: 305
Likes: 1
You said that the motor rebuilt, did you get steel gears installed? Not to insult your intelligence, but the 300 (unlike a V6 or 8) has a gear driven cam, not a chain & they are known to be noisy. Later 300s had a fiber gear which is quieter, but not very sturdy. If you had new, metal gears installed that may be what you're hearing. Just a thought.
Edwin
Edwin
Freshman User
Joined: Mar 2004
Posts: 37
Likes: 0
From: Boise, ID
I had a whine in my truck that started just when I accelerated and it wasnt all the time and then it became all the time and just kept getting worse.. turned out the exhaust manifold gasket was bad and it was sucking it causing the whine. I suggest you get a buddy in the truck to give it some gas and then you can take a small pipe or tube 18 inches long or whatever and use it to locate the source of the noise. I used some 3/4 or 1inch PVC... One end to your ear and the other over the motor and you should be able to detect where its coming from. Just move it around until its gets louder. Thats how I finally found my exhaust leak.. but even if its a belt or something else you should be able to locate the source.
Thread
Thread Starter
Forum
Replies
Last Post
Paul Moody
1997 - 2006 Expedition & Navigator
7
Jul 14, 2012 12:30 PM
