Hi all, today i noticed an odd noise under the hood of my 2000 f-150 5.4 with 141k miles on it. it sounds like a fan winding down, or maybe a rotating assembly winding down. as odd as it sounds, it seems to be coming from the passenger side under the valve cover (or somewhere in that area). it only makes this sound AFTER you shut the engine off and AFTER the engine has come to a complete stop. the fan and all the rotating parts (alt., a/c, water pump, etc) have long stopped and i still hear this "rotating assembly" winding down.

has anyone heard of this before? thanks for any help :-)

 

Are you sure it sounds like a mechanical device?

Once the engine stops, the cooling and A/C systems pressures will stabilize ... which can sound like the air being slowly let out a baloon.

For a moment, I was thinking that it might be the ABS pump being noisy or winding down.... but that would be on the drivers side I suppose...

Then again, it could be the cabin fan under the dash winding down, too... Mine was noisy until it was replaced, and sounded just like that.

 

i thought all those same things. however the fan is completely turned off (although i turned it on and tested just to be sure nothing changed, it didnt). the cabin fan sounded like a no brainer to me because it kinda sounds like its in that general area. i crawled up under the truck and had someone turn the engine off and its seems to be louder from the underside but still coming from the same area of the engine. im at a complete loss here. there are no codes being thrown by the computer, all the gauges look fine, no leaks what so ever.

 

My truck has made that sound from the day it was new.
I still haven't figured it out...lol

Phil

 

It's your EVR valve. Open your hood before shut down. Shut the engine off, get under your hood and put your hand on the EVR while it's humming a tune. You'll feel the vibration. Completely normal, it's vacuum just bleeding off thru the valve filter.

EVR ~