2004 Ranger XLT v6 4L, On cold start-up sometimes there is a grating sound for a second or two, sounds like something is trying to open. Is somewhat loud & can slightly feel the vibrations of the sound. Feel as if it's some type of air valve / flapper having a hard time opening. ???

 

A little more into

Does it make the sound when key is turned on?
Fuel pump should come on for 2 seconds with the key and then shut off

Does it make the sound only when cranking engine?
Could be starter relay/solenoid is arcing.

Does it make the sound just after engine starts?
There is an air preheater on the air inlet tube, between rad support and air cleaner box, it has a flap that closes and pulls air from around exhaust manifold until engine warms up.

 

It makes the sound immediately after engine start, dont believe starter or fuel pump problem, gut instinct is possibly some type of flapper / valve having hard time opening
in engine air sys. The flap for preheater you mentioned will check. How is the flap actuated.

 

It is vacuum operated, although can't say for sure on '04.

If noise is just after starting it could be timing chain cassette issue starting to show up, '04 was still using the older design I believe.
4.0l SOHC engines had a bad design on the timing chain setup.

Earlier TSB covered these models
Ford: 99-02 Explorer, 01-02 Sport Trac, Explorer Sport, Ranger
Mercury: 99-02 Mountaineer
*Engine - 4.0L SOHC - Rattle noise from primary chain drive area between 2K-3K RPM - Cold engine operation only

*Noise - Rattle noise from primary timing chain drive area between 2K-3K RPM - Cold engine operation only - vehicles equipped with 4.0L SOHC Engine only
Not sure if '04 would be effected

And your noise sounds different, just speculating

 

I havent been able to go outside & try to check flap for preheater, (both my wife & 2 girlfriends dont want me to be outside right now it's too cold, were down into the LOW 60's right now). Did look thru site for noises related to mine & found someone who posted in 2009 about a noise & made a video so we could hear it but video doesn't play anymore he did say that he suspected it might be, "sounds like the back part of the motor closer to the firewall", not sure what he's talking about though. I know your in BC bet it's a little lower than the 60's.

 

Ron your knowledge is leaps and bounds greater than mine, but I remember doing some research a while back on the '04 4.0L (I have an 04) and the 04s DO NOT have the older/bad timing chain design.

 

Very happy to hear that the problem with the chain cassettes does not include my model.
Have a neighbor who has pulled his engine out (explorer) to repair chain problem. He warned me that my ranger may go thru same someday.

 

Good info.

But.............not sure I trust a manufacturer to through out new, old parts, that were only 25% defective, maybe they did, I know the issue was reduced in later models.