Gas expanding and leaking out of tank in heated garage

Matt Rain

Matt Rain

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So I just secured a parking spot in my building's underground garage. The garage is kept really warm, about 25 degrees. The first time I parked my bike there, it had a full tank of gas and gas expanded so much that quite a bit of it ended up leaking out of the float bowls and out the gas cap key hole. Some of it made its way into the air box and ruined my air filter.

I checked the tank's vent hose and it's not blocked. BTW even with a fraction of a tank of gas (less than 1/4), vapors collect inside the cap and some of them liquefy on top of the cap.

I think the combination of an air-cooled bike, a full tank of gas and a wide temperature swing is causing this, but I'm wondering if that's normal.

When I park the bike outside, it's fine. I guess for now, I have to first park it outside, let it cool down then bring it in... that doesn't seem normal.

Help?
 
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Theres a reason why gas is kept at 15 degrees(?) i believe this is what is the standard temp to measure the volume of gas as it is dispensed. Gas volume is proportional to the temp. Temp up = gas volume up and vice versa. If you drive a cage, you may notice that a 50 L gas fill up seems to be more during the summer than winter. Although this is the case, all in all. You get the same amount of gas atoms/particles from the pump be it winter or summer. It just expands or shrinks depending on the temperature
 
I totally get that. I've just never heard of a car that leaked gas after filling up in the cold.
 
Yeap happened to me first time I rolled my bike inside for storage. The year after that I left the gas cap open until the temp equalized.
 
Matt Rain said:
I totally get that. I've just never heard of a car that leaked gas after filling up in the cold.
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thats because a car's tank never really gets filled up all the way because of the nozzle shorting when it detects gas. You should notice this when you prepay for $100 and it stops before this amount (assuming you have a 50-75 litre tank). If you want to fill your car all the way, use a jerry can to top it off.
 
really? a 15 degree C temp change should only result in 1 L of gas expanding 50mL. (sorry roughly calc based on google search)

at a full tank of 15L x 50 ml = ~750mL provided such a huge temp diff. I guess its possible

Are you filling it up super cold right up to the brim?




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The standard coefficient of gasoline’s expansion/contraction equals 0.069 % per degree Fahrenheit.
Source: http://www.consumerwatchdog.org/resources/DPReportHotFuelUSAJune07.pdf
And wikipedia for thermal expansion for volumetric coefficieint: http://en.wikipedia.org/wiki/Thermal_expansion
 
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Kuro said:
Are you filling it up super cold right up to the brim?
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No. And like I said even with 1/4 tank I get a small leak out of the cap.

Using my new infrared thermometer last night, the engine head was still at 85C about an hour after parking it. The gas was at 33C. That seems quite high.
 
Matt Rain said:
No. And like I said even with 1/4 tank I get a small leak out of the cap.

Using my new infrared thermometer last night, the engine head was still at 85C about an hour after parking it. The gas was at 33C. That seems quite high.
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Either a bad cap or you never aime when filling up ;)
 
Kuro said:
really? a 15 degree C temp change should only result in 1 L of gas expanding 50mL. (sorry roughly calc based on google search)

at a full tank of 15L x 50 ml = ~750mL provided such a huge temp diff. I guess its possible

Are you filling it up super cold right up to the brim?




-----------------------------------------------
The standard coefficient of gasoline’s expansion/contraction equals 0.069 % per degree Fahrenheit.
Source: http://www.consumerwatchdog.org/resources/DPReportHotFuelUSAJune07.pdf
And wikipedia for thermal expansion for volumetric coefficieint: http://en.wikipedia.org/wiki/Thermal_expansion
Click to expand...
Won't air expand more than liquid with heat? It will force the juice out somewhere (dunno how the vent works, but my tank was almost empty when it happened to me).
 
Cap is brand new... now that I think about it the old one was also leaking through the key hole in the summer heat... thought it was bad so I bought an OEM replacement.
 
fastar1 said:
Won't air expand more than liquid with heat? It will force the juice out somewhere (dunno how the vent works, but my tank was almost empty when it happened to me).
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the air would escape through the vent before pushing any gas anywhere.
 
Matt Rain said:
Cap is brand new... now that I think about it the old one was also leaking through the key hole in the summer heat... thought it was bad so I bought an OEM replacement.
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New or not your vent in your cap is not working properly....

I have kawis and keep them indoors and you can hear them vent randomly, via a little hissing sound coming from the caps....Yours is not working for whatever reason
 
That does sound like it. When I went to check the bike yesterday it looked fine, but when I sat on it and rocked it forward to get off the center stand the cap suddenly started hissing and a whole bunch of gas poured out.
 
So I've been playing with my infrared thermometer a bit. I stood by the bike for a good 15 minutes, monitoring the temperature of the head's fins and the fuel. I think the gas cap is overwhelmed by the extreme temperature swing when I go from moving through 5C weather and stopping the bike in a 25C garage. The fuel quickly goes from roughly 10C to 25C even with the gas cap off. Takes about 5 minutes.

I'm thinking that the best solution might be to insulate the bottom of the tank. Has anyone done something like this? What would you use?
 
Royal distributing sells it, called "adhesive heat shield" page 247 in the catalog. Made by moose racing $24.99 for an 18"x18" sheet. I use it on my dirtbikes to keep the gas from getting too hot.
 
Drain the gas? The reason that tanks are full is to eliminate condensation/rust. If the space is a constant temp there will be no condensation anyway and having a full tank is unnecessary.
 
Iceman said:
Royal distributing sells it, called "adhesive heat shield" page 247 in the catalog. Made by moose racing $24.99 for an 18"x18" sheet. I use it on my dirtbikes to keep the gas from getting too hot.
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Awesome, thanks!
 
Atleast your key lock won't rust.. wait its aluminum, just fill it less. /thread
 
A bunch of you have major reading comprehension issues. I'm going to fill less full but only cause I suspect that long term exposure to gas fumes is fokking the brain.
 
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