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I have a 2015 m3 touring with the 2.0. When I fill the car and put it in reverse I can hear a thumping sound when I apply the breaks, it appears to be coming from the gas tank. Does anyone else have this?
 

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Discussion Starter · #2 ·
Tank has to be full to hear it, I don't hear it after the gas goes down a little! I think it may be the fuel sloshing in the tank with not to much room to move and hitting the top of the tank. Hence the thumping noise!!! Anyone else with this issue?
 

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Noises can be VERY hard to trace and the sound can travel making you think it is coming from one area but in fact it is coming from another. Have a friend listen out side of the car for the sound. Just please do not run over your friend.
 

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Tank has to be full to hear it, I don't hear it after the gas goes down a little! I think it may be the fuel sloshing in the tank with not to much room to move and hitting the top of the tank. Hence the thumping noise!!! Anyone else with this issue?
I agree, I think it's fuel sloshing/slapping the tank top or filler neck opening.
 

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I agree, I think it's fuel sloshing/slapping the tank top or filler neck opening.
I agree. I would not worry to much unless it gets louder. You could always try and gun it in first and then break real hard to see if it happens that way.
 

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I posted a topic on this (I think). I have the answer to your problem. I too have the same issue, 2.5, 2.0 hatch or sedan. What's happening is that when you fill the gas tank, the baffolds (also know as the floatation device) that measures fuel rises to the top and is ever so slightly vibrating/banging the top of the gas tank, hence when your fuel level drops a bit the noise is gone. This is a know issue. I have (2) Mazda3's (both 2014's) and they both experience this issue. Mazda doesn't have a correction at this time. It sounds like the muffler is rumbling/loose. Anyways, there you have it!
 

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I'm having this exact same issue in a brand new 2017 Mazda 3 (Hatch). If I push up and down on the rear I can reproduce it. It DEFINITELY sounds like gas sloshing around, but with extra "thuds" or something banging up against something like the previous poster mentioned.

Right now, my tank is pretty full. I will see if it continues when tank is not so full.
 

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And btw....just for added context....I had Mazda change the entire fuel tank on my car - the issues was never resolved. This has actually been an issues on Mazda 3's for a long time...my 2011 exhibited this issue.
 

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I took my 17 gt to the dealer for the exact issue. They kept the car for 2 nights and concluded that's the nature of the car...the noise wont go away until it's down to less than half the tank.
 

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Thumping noise from gas tank

I have the new 2019 mazda 3 sport. And it still has this issue when the gas tank is full. Has anyone brought this up to mazda?
 

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I haven't noticed this noise on my Mazda 3 saloon / fastback but my father has a Nissan which makes this noise when the fuel tank is full. It's definitely fuel sloshing about between the baffles.
 

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End links loose ?
 
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