what could possibly be scratching the bottom of the fuel tank

[johnnash]

The fuel tank's recently developed a rattling sound which occurs when I speed up or brake, as if something was scratching the bottom of the fuel tank. It's on the rear right(passenger) side.

I haven't taken out the fuel pump to take a look inside (easiest way to access inside the tank I guess?) So I'm just curious and want to know what I'm dealing with. What could possibly be scratching the right bottom of the fuel tank...

[ghettosled]

does it sound like its sloshing around with the fuel? i cant think of anything in there that could have broken off but still have the car function normally. are you positive it isnt something with the exhaust or suspension?

[73sport]

Originally Posted by ghettosled

does it sound like its sloshing around with the fuel? i cant think of anything in there that could have broken off but still have the car function normally. are you positive it isnt something with the exhaust or suspension?

^^^ Ditto!

Unless the flap at the nozzle fill (just below gas cap) broke free or something from the fuel fill nozzle it self fell in. [Deliberate teen prank?]

PS - if you conclude its in the tank, looking is toxic so sticking your head close to the opening is just not healthy. Be careful not to generate static electricity and use a good mirror and flashlight.

[johnnash]

It sounds metalic first of all.
It occurs when I accelerate or brake medium hard.
It sounds like oscillation, ie. the thing is not just moving around, it's attached and follows a fixed trace.
I parked the car with the parking brake released and asked a friend to rock the car for me, and I got under the car and the biggest vibration came from the middle of the tank. (Which is why I suspected something in the tank.) By 3 and what ghettosled said, then the vibration is deceiving?

[johnnash]

Originally Posted by 73sport

^^^ Ditto!

Unless the flap at the nozzle fill (just below gas cap) broke free or something from the fuel fill nozzle it self fell in. [Deliberate teen prank?]

PS - if you conclude its in the tank, looking is toxic so sticking your head close to the opening is just not healthy. Be careful not to generate static electricity and use a good mirror and flashlight.

And I already did the health harm. Is there anything I can drink to cleanse myself? The car's been running so smooth and well, the metal against metal sound sounded so bad that it was like the car was falling apart which made me so frustrated....When the sound occurs, it's like someone rubbing my fuel tank with another piece of metal.

So I'm gonna widen my search. With the given symptoms, where would you guys check first?

[ghettosled]

does the oscillating noise sound in rythm to a wheel turning? do you have drum brakes on the rear? wondering if a dust shield is starting to scrape. i really have my doubts its something in the fuel tank. its a fairly closed system, and even if something did work its way it (something medal and heavy enough to sink) it would be very difficult for it to scrape and cause a loud enough noise to hear when driving.

going back to my brake idea. next time you hear the noise, gently apply the parking brake. put it on just hard enough to slow the car, but dont really wrench on it. did the sound change? did it go away?

[73sport]

Originally Posted by johnnash

And I already did the health harm. Is there anything I can drink to cleanse myself? The car's been running so smooth and well, the metal against metal sound sounded so bad that it was like the car was falling apart which made me so frustrated....When the sound occurs, it's like someone rubbing my fuel tank with another piece of metal.

So I'm gonna widen my search. With the given symptoms, where would you guys check first?

Chapstick, ball bearing, something round, fell from a pocket into the backseat and is rolling about under the seat????

[projektvertx]

Hmm, interesting ideas to take a look at. Let's throw out a couple more possibilities since me and johnnash are meeting tomorrow to take a look at this noise!

[johnnash]

Originally Posted by ghettosled

does the oscillating noise sound in rythm to a wheel turning? do you have drum brakes on the rear? wondering if a dust shield is starting to scrape. i really have my doubts its something in the fuel tank. its a fairly closed system, and even if something did work its way it (something medal and heavy enough to sink) it would be very difficult for it to scrape and cause a loud enough noise to hear when driving.

going back to my brake idea. next time you hear the noise, gently apply the parking brake. put it on just hard enough to slow the car, but dont really wrench on it. did the sound change? did it go away?

It's not in rhythm to the wheel turning but more in rhythm in acceleration. If I don't accelerate hard enough, i cannot hear it. Same goes with braking. But I'll try gently braking with handbrake.

I do have drum brakes on the rear. But I think it's a good possibility because prior to having the sound, there was some rust on the rear drum making a scratching sound and at the beginning, I didn't want to open the drum brake, so I kept the drum on and just span the drum around to sand it off. Then the drum came off after some spin and I put it back on. So I might have messed something up while sanding it when it's on? And it's not in rhythm with the wheel turning because it's not so loose that it's just scraping something constantly, but when I brake or accelerate hard enough, it's dislocated and starts to scrape things?

[johnnash]

Originally Posted by 73sport

Chapstick, ball bearing, something round, fell from a pocket into the backseat and is rolling about under the seat????

Nothing under the seat. I took the seat out and at the prime of my frustration, I even took the fuel pump out. But the gas tank is more complicated than a box, it has walls(and a smaller raised tank for the pump), so I couldn't see out of the fuel pump reservoir into the other side.

[73sport]

Originally Posted by johnnash

Nothing under the seat. I took the seat out and at the prime of my frustration, I even took the fuel pump out. But the gas tank is more complicated than a box, it has walls(and a smaller raised tank for the pump), so I couldn't see out of the fuel pump reservoir into the other side.

I bet a lighter would have helped see beyond that little optic blockage. . .

EDIT: J/K!

End result may go like this. . .

[projektvertx]

Originally Posted by 73sport

I bet a lighter would have helped see beyond that little optic blockage. . .

Although he wouldn't be seeing much else after wards

[projektvertx]

BUMP. Ok so me an Xin checked out the car today, and here are my general impressions of the car. I don't think it's the fuel tank, it wasn't moving, and the vibration felt internal, almost like it could be the floater in there or something (car had a quarter tank left, he'll fill it up and see if it changes, but I doubt it will). Also, fuel filler neck didn't move at all.

On another note, this only happens at slow speed acceleration or braking, not under normal driving conditions. I sprayed some cleaner on the inside of the drum, which we removed on both sides, the shoes looked fine, and parking brake engaged perfectly.

Also, he has the video of this, but in the vid I show how the muffler moves around A LOT, clanking the heat shield above it. The plastic retainers where flexing way more than I'd like. It's on the opposite side of the noise, but it's worth mentioning and may or may not be related. (Possible the exhaust pipe before the muffler clanking on the fuel tank?)

Also, both rear sway bar endlinks need to be replaced. When I pull at them, the balls move in the joint very dramatically.

On another note, the drums are rusted on the outside, but seem to be within specs. When we sanded a bit on the outside, the noise didn't really seem to change at all. Any ideas???

[SexieWASD]

I would remove everything from the trunk, including the spare and check in the rear quarter panels for anything, then see if it still makes sound.

I once had a customer come in who's car made an annoying squeaking sound in the back every time he would brake. He came in suggesting everything from struts to swaybar bushings and said that he had been dealing with the sound for months. After taking the car for a test drive it turned out that the jacket he had hanging in the back had a leather loop on it and was swinging back and forth on the hook making the sound.

[projektvertx]

^ Spare was out when we did this. Trunk was cluttered with tools from working, but the sound is coming from outside the car... (Interesting story thought, who would have thought?)