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Recently replaced gas tank is making a lot of sloshing noise

I had my gas tank replaced recently and upon replacing the tank, I now notice a sloshing sound when I stop my car. It sounds like I took a gallon milk jug and turned it over completely to pour everything out- glug glug glug. It seems to be coming from the fuel tank and the car rocks back and forth a lot. Also had work done on the struts at the same time. What is the cause of this and is it safe to operate? Is it reasonable to ask the mechanic to fix it? Is it possible that the wrong tank was put on my car? I’ve checked for information about this particular issue but have not seen any advice about this problem when it is resulting from a replaced part.

Make sure the gas tank straps are tight. That can cause a “sloshing” noise if it moves around. Another possibility is that the new tank may not have the same baffles as your old tank. Where did you get the new tank?

It could be that he replaced it with a tank without baffles.
Baffles are there to make sure the gas doesn’t slosh around too much.

Besides it being annoying, it could affect performance some:
Years ago, when dinosaurs roamed the plains and cars had carburetors, lots of tanks didn’t have baffles but when people converted these old cars to have fuel injection, they found that some cars would stutter a bit when you’re doing hard cornering.
The fuel pump would basically suck a slug of air at that point. You’d feel that in hesitation. Annoying because the main reason for changing these old cars to have fuel injection is performance and reliability.

I’d ask your mechanic whether this tank has baffles. Most modern fuel injected tanks should have them, I think.

I’d guess this is caused by what the other posters are saying – because they new tank doesn’t have the same baffling as the old. That doesn’t mean it is the “wrong tank” for your car, but it is probably an aftermarket tank not meeting OEM specs. You probably benefitted from this on the bill – the tank was less expensive than an OEM version would have been.

Baffles also help with the rocking. Gasoline weighs about 7 pounds per gallon, so 14 gallons of gas is about 98 pounds of dynamically moving weight if it is allowed to move around freely without baffles.

Sloshing is annoying.

Unbelievably Acura left out or under designed the baffles in my 2007 MDX when tank is full. It is subtle.

I had to replace the gas tank in my 66 Chevy pickup. It had the gas tank behind the seat. The new gas tank sloshed around so much (no baffles) that I removed the tank and installed it between the frame rails. I never noticed it after that.

Thanks for all of the helpful posts, I can tolerate the sloshing so long as everything is safe! I’ll stop worrying now.