Hey Guys, I just picked up my new '08 GT and have about 400 miles on it. The other day when sitting in my friends driveway showing him the car, I heard a knock or thump come from the car that sounded almost like someone bumped into my car. I thought maybe it was just a shift in the suspension, because my friend (who weights like 270lbs) had just shifted his weight. However, today my car did the same thing with just me in it and I wasn't moving. I'm really dumbfounded as to what this could be, but none the less it has me concerned, because I plan on keeping this car for a long time. Any thoughts? Is this normal in a new car? My '99 never did anything like this. Thanks for any thoughts or insights.

 

It could be the air conditioning compressor clutch engaging/disengaging, which is normal.

 

+1 on the AC compressor clutch. It's noisy when it engages.

 

Thanks guys. If it is the A/C, would it occur every time on turn on the A/C? ...same question with the clutch. I don't notice any movement per se in the car, or hear any changes in the RPM's, which is why I was completely baffled. Now, I'm trying to figure out how to recreate the noise so that I can narrow it down. I know this might be hard to diagnose over the web, but definitely appreciate all the help I can get.

 

If it is the ac, you would hear it each time the system cycles. It will do this (if memory serves me correctly) when ac is on, or when you have the controls set on the defrost setting. If you have your controls set to vent (no ac, no defrost) and hear it, it may be something else. Again, I'm doing this from memory, so anyone else feel free to jump in.

 

Tell your friend to go on the Subway diet... (j/k!)

Test your AC compressor by setting it to MAX AC, that should fire the compressor up. That being said, AC compressors should *not* be making a "knock" or "thump" when engaging... that suggests a problem with the compressor, since a "thump" means there is excessive drag on the belt system by the compressor.

Check your radiator fan for clearance - it could be knocking against something as it engages or maybe it is loose?

Do you have a stick or automatic? Have you done any mods?

Any way you slice it the sound is *not* normal and I would not accept it in a 400 mile brand new car. Dealer may need to be involved in this one... even if they tell you they "cannot duplicate the problem" at least you are on record as having the issue from day one.

 

OK, so I don't think it is the A/C, from what I can tell. I've turned it on and off a couple of times, let it run for awhile, etc. and the noise does not occur. I did swing by the dealer the other day and mentioned it to them, and they just said to let them know if it happens again. We let the car run for about 10 minutes in the lot and nothing.

A couple other reference points.....
-I have a manual transmission
-No Mods yet
-Both times the noise occured, the vehicle was in neutral
-Both days it occured, it was humid/rainy (not sure if that has anything to do with it or not, but I've noted it anyways)

mrkabc, good question on the fan, I'll have to take a look at that. I think I'll call the dealer again and simply ask my sales guy if he could ask the mechanics if they have any ideas or would be willing to take a look at it. I'm sure they would look at it, my concern is if it isn't easily replicated, that they'll just say they didn't see anything and cannot replicate it.

Any other ideas are more than welcome. This is bugging me, because it just seemed way too loud to be normal and I just bought the car $$$$$.

Thanks again everyone.

 

I get the exact same thing, have since I first got the car. Does it in neutral, too.

My mechanic said it had something to do with some sort of opening/closing in the HVAC system, and not to be concerned - whatever that means.

Only happens on occasion, and there is no perceivable pattern I can determine.

 

Hollywood_North GT,

Thanks for input. That is interesting. I'm glad to know I'm not the only one......of course, are we the only two? I'm curious why this would happen on our vehicles, but not others.

On a side note.....how did you get the info about your car such as serialized date, build week, etc?

 

Can't answer that, truthfully. But as my mechanic was completely unconcerned about it, I've given up worrying about it. Would be nice to know what is causing it, though, given that others don't seem to have the problem.

But if something suddenly goes haywire one day - and this sound is shown to be related to it - then I guess we will figure out what it was by default, and then you can rest assured I will stick Ford for the bill.

As I ordered the car, I was pretty much able to track and record all that info as I got it.

 

Hi UMich97,

I think I have the same issue here..

My car is 2008, with manual transmission and a very humid weather (80% or above over here!!!)

I did here the sound 3-4 time since I got the car (a month ago) and I can recall/confirm it ahppened on humid days and when car is at idle (almost 10 seconds after switching on the A/C)

Just like Hollywood_North GT said, I think it is related to the opening/closing in the HVAC system and I was never worried about it..

Just wanted to share this with you guys..

 

Hani, appreciate the additional input. Sounds like there are a couple of us out there experiencing this...which definitely makes me feel better.

Hollywood_NorthGT,

I think I'm going to try to find a good VIN decoder, so I can get my Stang's info too, since mine wasn't ordered, so no luck there.

 

UMich97,

I sent you a PM on Mustang info from VIN...