OK, first off, this is on a 2007 Screw FX4 5.4L, bone stock, 42k.

For the last several weeks my truck has made a loud sucking noise when i accelerate either from a dead stop or after a slow turn. It's been getting worse to the point where it does it almost every time. It only lasts about 5 sec and then goes away, until the next acceleration.

Truck has had all scheduled maintenance including oil changes, air filter, etc. No previous issues, no CEL.

I tried cleaning the MAF and seafoam treatment with no luck. Air filter looks fine.

Took the truck to the Ford Dealer and they were "unable to reproduce it" and gave it back to me without doing a thing. hmm, weird.

Thoughts?????????????

 

Weird. Maybe an issue with your fan clutch? Does it sound like the engine's fan?

 

It does, only 20x louder than it should

 

is this the first winter you've had the truck? sounds like your hearing the air going through the throttle body. do you have a K&N drop in air filter or anything like it?

 

Bought it new in '06 and it never did it up until recently. Truck is completely bone stock with the regular ford paper air filter. I originally thought the same thing also but it's intermittent, and crazy loud.

 

When the fan clutch engages fully, it makes a VERY loud roar noise... Just an idea...

 

I'm with you on this one. Sounds like it's engaging at high rpm when it shouldn't be. Gonna replace the fan clutch myself this week and see if it resolves.

 

I hope I gave you good advice.... Why don't you take the fan belt off and see if it still makes the noise. Just don't drive around long, cause the water pump won't be turning...

 

You say the air filter looks fine. But have you tried changing it after the noise began? Just a suggestion.