Banging Noise From Fuel Tank When Coming To Stop

[gsdog]

I have an 03 P-32, 75 gal fuel tank, when coming to a stop after driving, the gas tank makes a banging noise. The less fuel in the tank, the more hollow the sound. The tank appears to be expanding, since, standing in the motorhome over the tank, I can feel a severe vibration through the floor. I have loosened the fuel cap and, also,had a WCC repair center check vents. They could not find a problem. Any ideas?????? Thanks, George

[gsdog]

I have an 03 P-32, 75 gal fuel tank, when coming to a stop after driving, the gas tank makes a banging noise. The less fuel in the tank, the more hollow the sound. The tank appears to be expanding, since, standing in the motorhome over the tank, I can feel a severe vibration through the floor. I have loosened the fuel cap and, also,had a WCC repair center check vents. They could not find a problem. Any ideas?????? Thanks, George

[Bob (WA0MQE)]

You say a "severe vibration through the floor," is this with the engine running or not? The fuel pump is in the tank, so if your engine is running maybe this is what your feeling.

The fuel tank is a long ways from the drivers seat, so how can you tell for sure this banging is coming from the fuel tank?

[gsdog]

Good lead ,Bob. With the engine off, just parked, I went back to the bedroom, was standing drectly above fuel tank, when I felt an intense vibration and the banging noise. I think this noise is related to the expanding and contracting of the gas tank, itself. It must have something to do with a vent system, sucking in the tank and then letting loose and expanding when coming to a stop. If the fuel system is vented, I have to find the vent hoses, or some type of cannister and check for a blockage. Bob, thanks for trying to help me, this is been going on for quite awhile, It stopped for a small period of time and started, again.

[troth]

Letsee, there used to be a gas that would "Put a tiger in your tank..."

[John350]

Try changing your gas cap. The cap has pressure and vacuum relief built into it. When you park, try taking the gas cap off. You should not have a pressure or vacuum relief sound. Other than that, check the evaporative emissions system for proper operation.

[hwybnb]

This might sound a bit far fetched but a friend that lives in Nebraska told me that the same thing happened in his car a few winters ago. Turned out that it was a chunk of frozen water (ice) floating in the tank.

[gsdog]

I do remember Esso's tiger and the tails hanging out of gas caps.

It can't be ice, it also happens in hot weather.

I drove with the gas cap off and it still happened. No pressure when releasing cap, after, coming to a stop. I like the evaporater system idea, but, don't know where it is. Although, the WC repair center checked this and said it was not the problem. But, this was the same center that missed the broken strap on the front sway bar bushing and the power booster that wouldn't allow the brake pedal to return.

Men, thanks for all the help, it is driving me crazy. George

[JCM]

Could it be a worker from the manufacturing plant that fell asleep during a break and was welded into the tank or could it be a baffle that has come loose and moves around as you drive. Happened in a friend's Mountain Air.

[dieselclacker]

George, if like you say it still makes the noise with the gas cap removed, then you can eliminate the evaporatve recovery system, as that system depends on sealed fuel tank for its operation, and it would not be posssible for the tank to contract or expand with the tannk cap removed I would look for proper positioning of the tank between the frame rails, and security of mounting bolts and straps. And as someone else has mentioned, maybe a loose or broken baffle within the tank. Does the amount of fuel in the tank seem to make any difference?
Also, I would make sure it was the fuel tank making the noise, and not something else, suspension, etc.

Dieselclacker

[gsdog]

I tried to move the tank around and the straps, all seem tight. I hit the bottom of tank, repeatedly, noise stopped for that 400 mile trip. Noise came back, used a rubber mallet, at same location, noise did not stop. Noise has a more hollow noise, with less fuel in the tank. A loose or broken baffle was suspect. Again, had another shop check, this one said it was not a baffle. I think it is the baffle. Hear me out with this elimination idea and see if you think it makes sense. How about if I run the tank really low on fuel and hit it with the mallet. Do you think I will hear a metallic sound?