ever since my truck (5.4l '01 supercrew) was brand new i've always noticed what feels like a slight thunk within a few seconds after i fire up the engine. it is a sensation similar to that felt when the a/c compressor kicks in. however, my truck always does this, even with the climate controls on off. anyone know what that noise/vibration sensation is and what causes it, some kind of fan clutch or something? not really worried about it, just curious if anyone else has noticed similar...

 

It happens to me every once in a while...an audible (also felt) thump or crunch that comes from the engine bay on statrup. I think it's either the belt tensioner or the compressor. It only happens once during the day right at initial morning startup.

Anyone have any ideas. My '99SC has about 27k miles now.

 

thanks marv,

i guess noboby else experiences this noise, or somebody surely would have posted, right?

 

It has been my experience that that thunk noise is related to the a/c accumulator. Aske your Ford Dealer to check TSB's under "Climate Control" I've seen many trucks repaired by replacing the accumulator per the TSB.

 

excuse me for being dumb, but what is the a/c accumulator?

 

[QUOTE]Originally posted by unclebeldin
It has been my experience that that thunk noise is related to the a/c accumulator. Aske your Ford Dealer to check TSB's under "Climate Control" I've seen many trucks repaired by replacing the accumulator per the TSB. [/QUOTE

I've heard and felt the same "thunk" when I start my truck in the morning, but would the a/c accumulator make this noise if the a/c or defrost were not on? I've only had this truck for about a month, and it has done it since day 1. My '00 never made this noise.

 

My '00 makes that noise... sounds like it's a part of the self test for the transfer case, but I could be wrong... it's going in to the dealer on the 17th for that (along with a host of other things). I'll let you know if they find anything.

-Joe-

 

Could it possibly be the cooling fan engaging? I have noticed that I always hear the rushing noise from the fan a few seconds after I fist start my engine, but I don't believe I have ever noticed a clunking noise. Just a thought...

 

Are you sure the a/c is in the OFF, Panel, or Floor postion when you hear this thunk sound? In any other position, the a/c compressor will operate. If you don't hear the thunk when you start the truck with the a/c in the positions I mentioned, then it's not the normal sound of the compressor after sitting for a day or two.

 

Both my F150 and my wifes Expedition make this sound. Although, the truck is a bit more pronounced. I have to agree with GIJoecam, sounds like the transfer case.

I still hear it even if I don't start the engine, but just turn the key. Just one of those cool things about our trucks???!!!

 

it makes this thunk sound/vibration no matter what position the climate control is set at...even off.

as for the info on transfer case self testing...i've never heard of such a thing. can anyone explain more about this? there certainly isn't an idiot light on the dash that says your transfer case test has failed!!

 

by golly, last night i thought i'd just turn the ignition on without starting the truck and guess what, i got the thunk! i had always thought it was related to the engine starting. guess not!

so, this thunk is supposedly a transfer case self test? anyone wanna explain this?

 

I wonder if it could be related to the ABS or the fuel system. My thunks happen righ after the ABS light goes out..

 

that makes much more sense to me! come to think of it, i've had a couple cars that made a similar type noise right after startup. i think you might be on to something...thanks for the feedback...

 

Hmmm... Interesting TroyK

I took delivery of my truck on 11/20/2000 and have had absolutely no problems with it so far. Greatest ride I've ever owned, by far. However...

Two weeks ago I started it up, first thing in the morning and,
KACHUNK !
I honestly thought either the belt had broken or that I'd just sent the neighbors cat (sleeping in the fan bay) to that great milk bowl in the sky.

It hasn't happened again and nothing seems wrong but whatever caused the noise was definitely too loud to be "as designed". Much louder than compressor engaging unless the compressor was maybe right at the top or bottom of its stroke...?

Anyway, just wanted to let you know that I had the same experience once, and hope it was the last, although I doubt it.