I bought 07 F150 XLT from my brother almost 2 months ago. It has 55500 miles on the 5.4L V8 and I just recently started hearing a strange engine noise. Its hard to explain but it kind of sounds like a fan noise or alternator or something electrical. It gets worse when accelerating. I'm not sure if his warranty can transfer to me but I'm just wondering if anyone else has had this and knows what it could be.

 

AC Clutch, Alternator bearings, tensioner, etc... ? (first guesses) Can you tell which side/top/bottom the noise is coming from? Does it do it at idle or only while moving?

Take the belt off and start spinning things to see which it is. IMO go ahead and replace the belt with the offending part if any of the above are bad.

 

It makes the noise at idle too but is more pronounced when accelerating or just hitting the gas while parked. I can only tell that it is coming from the engine compartment.

 

It's gotta be one of the above mentioned items...never by a truck from a relative...lol

 

You can sometimes look at the alternator and see it shaking wildly if it's alternator bearings; wouldn't hurt to take it to an auto shop and have them check your battery + alternator for charging abnormality (usually check it for free). Although it may not show a charging abnormality even if it is the alternator, at the very least another set of eyes that see alternators every day might help you deduce.

 

It happens when idling also but is more pronounced when accelerating or hitting the gas while parked. I can only tell that its coming from the engine compartment. Not sure what side though.

 

Ok thanks. I will look at it more closely and probably take it somewhere. Trying to get it taken care of before driving to Chicago from Cincinnati in 2 weeks.

 

My mechanic crawled around under my truck for about 10 minutes before finding a strange rattle that I thought was coming from the rear engine compartment. It turned out to be the cat. converter. seems something inside has broken off and is rolling vibrating when the frequency is just right, usually at low speeds and when going down hill with the foot off the accelerator.

The good news was he said there was no charge, but I tipped him $20 for lunch.

Moral of this story, is get a good mechanic to see if he can isolate and thereby identify the noise source before throwing money at it.

Good luck.

 

From what I can tell, it sounds like it is coming from the front of the engine so I'm thinking that could mean fan, pulleys, belts, pretty much any moving part up there. And it gets worse as the RPMs increase. The alternator doesn't appear to be shaking either.