This is regarding my 2006 Mustang GT. Perhaps you've heard of her.

I did a very small search, but it didn't show much. I gotta go to work, but I wanna ask this question.

Sometimes, but not all the time, when I use a climate control setting that requires the A/C to be on (defrost, Max A/C) there will be the requisite sound of the A/C compressor clutch coming on. No big deal, know what that's like, although it does seem rather... loudish? But hasn't changed since I've owned the car. That sounds, properly, like it's coming from the front right side of the car, where the compressor is. No weirdness there, but...

About 75%? of the time there will quickly follow a very loud pop, or bang, and it sounds like it's coming from the LEFT side of the car, near the firewall. As I'm in the car I can't really deduce if it's inside the cockpit or in the engine bay somewhere, but last time I heard it, it seriously sounded like it was somewhere above the pedals, but in all cases, right side, somewhere close to the firewall... or so it sounds.

I'm not real sure what it is, why it's happening. I can't recreate it on command. Seems to be, perhaps, temperature related? I'm tryin' to figure it out so I *can* recreate it. Although it seems to be only when the car has been sitting, and not started for a while. Cold, as it were.

The car is not in motion when this happens, just sitting there, first start. If the A/C is kept off, it will not do it. If you have the A/C on when the car is started, it will, when it decides to, do the noise. If you wait a few minutes... it may also do the noise.

I'm not remembering anytime where the car is warmed up that it does it, although I could be mistaken on that issue. It seems to be a cold start, and even then it may not do it. When I attempted to recreate on command... it of course decided to be coy about it. Silly car.

About as complete a description I've got. I'm not *terribly* concered about it, nothing seems to be flying off the car in a horrible explosion or such, and all systems do continue to work fine. I was just wondering if there was an explanation you guys might have, a similar experience that's been resolved somehow.

I probably talked too much about it, huh? Ah well.

Thanks in advance!

/Mods, if this is in the wrong place... well, I apologize. It's sorta a service issue? If not, please move, and thanks much! Y'all do a great job here, it's us weirdos who don't know where things go that mess it all up...

 

There is a canister on left side by the firewall for the A/C system,
think it's called "expansion tank", check to see if any of those lines
are close enough to hit any thing if they flex when system comes on
or if tank mounting might be loose.
Does your A/C cool okay, don't know if being a little low on gas might
cause pressure spike noise.

 

Seems to cool fine to me... I"ll have the pressures checked and look for that cannister situation. Thanks much!

 

I had the same thing happen in my 07 gt. As soon as I start the car it happens usually within the first 10 seconds of ignition. Sounds like a mallet hitting the firewall.

 

I get the same thing about 10% of the time. I can feel it in my feet too, it's like a loud THUNK.

 

Yeah, exactly, a mallet. *THWACK!* Can't believe anyone hasn't spoken up sayin' "Yeah, it's the frammitz. It just needs tightening." or some other similar statement.

I've honestly been swamped myself, and/or sickish, and haven't looked yet. Last time I tried, it *never did it*. Real irritating, that.

 

Hmm weird never hear of it, maybe it's a "BANG! summers here!"

 

Could it have something to do with the vents opening up when the A/C is turned on , or the A/C clutch ?

 

Mine doesn't do that.

 

my 05 did the twack as well as my 07 there had been talk on this before somewhere here I just gave up on it, I as well thought vents but it sounds more under the hood drivers side I think.

 

My 2005 does something similar. I can actually feel it thru the steering column. I'd almost bet it's a clutch issue; a friend's was doing the same thing, and his clutch pulley completely froze up.