Gas fuel tank leak pressure test check before paint

concours

concours

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3 PSI max.

Soap & water.
Gas fuel tank leak pressure test check before paint
 
concours said:
To clarify, I used soapy water to leak check.

As for "holding pressure", I do not valve it off, and wait. Reason being, the block off bungs may not be a perfect seal, creating a false negative test.
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Good method.
I tried to pressurize a duck decoy in an attempt to blow the water out of it...but I forgot to lower the pressure on my compressor's output.
Boy did that not work.
 
I took the low tech approach using a latex glove over the filler neck, a hose off one of the taps and a little lung pressure into tank. Inflated glove. Tap shut off. Soapy water sprayed all about. Glove stayed inflated, no bubbles seen. Jobs a good-un!
 
Lineslinger said:
I was holding the hard plastic decoy in my lap when overpressure did it's thing, took me about ten minutes before the "boys' felt well enough to get up from the floor.
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Sorry, didn't mean to put a like on this post...was looking for something like this 😧😵😖
 
Lineslinger said:
I was holding the hard plastic decoy in my lap when overpressure did it's thing, took me about ten minutes before the "boys' felt well enough to get up from the floor.
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Ice.
Ice will make the boys feel better
 
Please don't remind me, there is a thread somewhere where I asked about the stud spacing at the front of the tank.

That thread confirmed why when I got the bike one hole in the frame attachment wings was widened to accommodate the studs.
It must have been pressure checked and over pressured even though not obvious to the eye spreading the tank and then widening the stud spacing.

I had been tempted to fit some form of turnbuckle to the studs and give it a tweak (once a week perhaps) to try and slowly get them back to something stock but was a chicken.
They got machined offsets (insets ?) instead.

Gas fuel tank leak pressure test check before paint


There was a member in the past that I recall (built his 850 from a frame and then bought parts as he progressed) got a tank tested at a radiator shop and they near turned it into a puffer fish.... Whoops.
 
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I bought a 68 Triumph Bonneville that the previous owner did a pressure test on the fuel tank, and it spread the sides of the tank. It was a shame because he decided to do this after he had put a nice paint job on it too.

Mark
 
I check a different way. I fill it to the brim with Evaporust and let it sit on a clean/dry counter overnight. If the counter is dry the next day, it is leak-free and any internal rust is removed.
 
marshg246 said:
I check a different way. I fill it to the brim with Evaporust and let it sit on a clean/dry counter overnight. If the counter is dry the next day, it is leak-free and any internal rust is removed.
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How does this pin point the leak/leaks if you have them?
 
baz said:
How does this pin point the leak/leaks if you have them?
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The outside of the tank will be wet in the area - not pinpoint. Most have no leak. If there is a leak then more work is required depending on where and how bad.

I started this due to a Triumph tank. The air pressure test said no leak. The tank had some rust so I filled it with Evaporust to remove it. The next morning the Evaporust was all over the place (expensive loss). The front mount of those tanks has a front mounting cylinder and threaded plate welded to each side of the front of the tank. The rust was in the void and when Evaporust removed the rust, there was a 1/4" hole in the tank above the mount!
 
marshg246 said:
The outside of the tank will be wet in the area - not pinpoint. Most have no leak. If there is a leak then more work is required depending on where and how bad.

I started this due to a Triumph tank. The air pressure test said no leak. The tank had some rust so I filled it with Evaporust to remove it. The next morning the Evaporust was all over the place (expensive loss). The front mount of those tanks has a front mounting cylinder and threaded plate welded to each side of the front of the tank. The rust was in the void and when Evaporust removed the rust, there was a 1/4" hole in the tank above the mount!
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A 1/4" hole full of rust that didn't leak? That's pretty bad !
When I've had to take the bottom of a tank out I always put a few psi in the tank to check the seams after I've welded it back in
I almost ruined a bsa tank many years ago when I gave it a squirt with an airline and put 18psi in 🙄🙄
 
oleblu72 said:
I bought a 68 Triumph Bonneville that the previous owner did a pressure test on the fuel tank, and it spread the sides of the tank. It was a shame because he decided to do this after he had put a nice paint job on it too.

Mark
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The very reason I created the thread, to have a searchable title, and remove ambiguity regarding pressure testing. Clearly more than a few tanks (and decoys) have been sacrificed at the alter. 😱
 
baz said:
A 1/4" hole full of rust that didn't leak? That's pretty bad !
When I've had to take the bottom of a tank out I always put a few psi in the tank to check the seams after I've welded it back in
I almost ruined a bsa tank many years ago when I gave it a squirt with an airline and put 18psi in 🙄🙄
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Ya, the really interesting part was that we cut the mount off, found the good edge of the rusted area (made about a 3/4" hole, welded a circle over it, and rebuilt the mount. It appeared it actually rusted from the outside in as they are painted after the mount is installed. Took the other side off and it was only surface rust there. Several years later and the tank is fine.
 
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