My '06 F250 XL with 219,000km has started to make a sound somewhere between a grind and a clunk. This sound is very brief (half a second) and occurs about 3 or 4 seconds after I start the truck. The sound seems to be coming from the mid/front under the hood maybe a little more on the passenger side than the drivers side.

It has been doing this for a couple months and only on cold starts - but not every cold start (only every 3 starts or so.) I completely changed all fluids recently and the truck is not throwing a code and is giving me no other problems at all, other than that brief sound on startup.

Any ideas folks?

 

Mine does the same thing I have never been able to isolate it and nothing seems to be amiss. Mine however is just a loud "clunk" never a grinding sound.

 

Mine does this on cold starts if I leave the A/C or Defrost on. It's when the A/C compressor kicks on the first time after it's been sitting awhile.
JL

 

Pretty sure it's the A/C compressor/clutch, my wife's '05 Explorer does the same thing if you leave the A/C or Defrost on.

 

Yep, mine too. It comes on with A/C

 

My 2000 F250 has been doing this same type of thing lately too. I haven't been running the AC lately because of winter weather but upon startup,(especially cold) immediately after the motor fires I will get a rough (is the only way that I can describe it) sound that comes from my engine compartment that sounds like it is coming from the passenger side of the motor and the only thing that I can think (or the theory that I have come to lately) is that my starter may be going out and is not retracting from the flywheel quickly enough. Any other theories I may consider?

 

A/C is not the only position that the compressor engages on.
JL

 

Oddly enough, the a/c is generally used with the heater to reduce windshield fogging when the defroster is on. You might try unplugging it for diagnostic purposes.....

 

yup..compressor...mine has always done this. No worries.

 

Sounds terrible doesn't it.....
I was surprised the first few times mine did that.
JL

 

Mine does it too occasionally. As does my Dad's 2002 Explorer.

 

Yes... Freaked me out at first!

 

Mine still freaks me out due to how loud it is.

 

Your right it is my compressor making that horrible sound, interesting!

 

Mine has always done this, and now reading what it is, it makes me feel much better. Everything still worked after I heard it, so I just blew it off. My wife heard it, and asked how much that was going to cost...