Clunk Clunk
 

Greetings and Felicitations Mazda3 friends,
I've have a particular problem for the past year with my 2007 Mazda3s hatchback. Every time I begin driving after being parked overnight or even after an hour or so, I get a single CLUNK from underneath the chassis. It sounds like a small wrench being dropped into a can. It occurs ONLY ONCE after starting up and traveling less than a city block and is always noticeable at slow speeds. When I initially asked the dealer about it several months ago, they could not find any problem but the noise was less prominent then. There seems to be no performance issues related to the clunk but it is still there and I am concerned about a future post-warranty issue. Could it be an exhaust or catalytic converter problem since the engine and exhaust are cold at startup but once it starts heating up the problem disappears until the car sits for a time. Upon restarting and moving, the single CLUNK occurs again. Any thoughts? Quite perplexed!

hmmmm can you tell where under the car it comes from(trans, axels, near the belts further back?)... do you have an automatic trans or manual?

d-machine,
Hard to tell while sitting in the vehicle but my one-time clunk seems to be no further forward than the transmission and may be more to the rear than that. This is a 5-speed automatic transmission with the sport shift feature.

i get a slight tick/clunk noise when i first accelerate from reversing or being parked... i have the 4 speed auto... i also get a clunk when i shift into reverse after the car has cooled.. i havent narrowed doen the problem, but i know it went away for a few months after i did a full transmission fluid flush and changed the trans filter

I hear a slight noise...maybe a click more than a clunk...under the same conditions wmkudirka described. I never heard it before until I started to listen for it. It sounds like a relay to me.

Same problem
 

I have a 2005 Mazda 3 5dr w/ Manual Transmission, and am experiencing the same clunking noise.

I first noticed it after I had the rear brakes serviced back in April. Of course, I was probably just more sensitive to it at that point. The sound seems to be coming from the back of the car.

Also, I have recently noticed a burning smell after driving. It seems to be coming from the left rear brake. It is very hot after driving in traffic. I am wondering if somehow the parking brake is engaged while driving. No pull, or drag is noticable however.

I'm puzzled.

I now perceive this noise to be more like the AC compressor kicking on (if indeed we are speaking of the same "clunk")

I'm always open to new ideas and thoughts about this particular noise. However, I wouldn't think it's related to the AC because it only occurs once when the car is put into motion after being parked and the engine off for a brief/or long period. The AC compressor on the other hand cycles on and off while driving and the sound I hear does not keep repeating itself.

Me Too!
 

OK....have noticed this for a few weeks also on my 07 2.3 5door. To me it sounds like something making a one-time bumping into something, like a socket rolling against the inside of a fender. Usually happens after moving a few car lengths. It is hardly noticable and can't hear it over the radio. Any guesses?

bztony,
I'm completely baffled as well. The one time thump is so predictable. Occurs with every time the car leaves the garage or after being parked and shut off. Always occurs with 500 feet after starting up and at low speed and rpm. At least, that is when it is most noticeable.

Sorry to revive such an old thread... But, has anyone had any luck pinning down what's causing this?

You had me confused until I realized that I figured out what this noise was within a few weeks of buying my 3. It happens on all models, any trans / trim level.

It occurs after passing ~13MPH for the first time after the vehicle is started. It's a self test or something in the ABS system, the clink is the sound of the brake lines rattling as whatever clicks. I posted this Q a long while back and apparently it is on the protoge models as well. Nothing to be concerned with though.

Sounds reasonable
 

The self test idea sounds good. I now listen for the noise and its there like clockwork. Now if I could get those darn brakes to quit squeeling when I back out of the driveway.........

The 2007 has a weight on the front calipers that is a fix for earlier models brake squeeling - looks like an out of place weight on the caliper.
But brake squeeling could be due to a dragging caliper, which i've had on my car a number of times. If the caliper is sticking, you could be pushing on just one side of the disk - with the other pad not moving much and likely to squeel. Especially if it's been 'light' for a while and there's a buildup of corrosion.
I finally put anti-sieze on the caliper pins which so far is a lot better than any of the caliper greases i've tried.