# Fuel Tank Bubbling



## wrmdunker

I have a White 18 hp lawn tractor with a Briggs V twin. A 2000 model year with 725 hours on it.

Mowed the other day,shut down, opened the hood to help with cooldown and I noticed gas wetting the area around the fuel cap and thought that odd. Removed the cap and noticed some pretty significant bubble streams rising inside the tank. I have not seen this before. Went on for several minutes.

Seemed to be originating in the bottom tank outlet area. Wondered if I was boiling the gas so I stuck a good thermometer in and it hit 120 F.

Am I running so hot to boil gas? Is this air backfeed out of the carb? Is this a problem with the cap?

Thanks all.


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## Ed_GT5000

I remember another thread reporting the same problem. I suggested using better fuel. another poster suggested checking the fuel line routing. I don't know if the problem was solved. The cap could be the problem if it was not venting and allowing slightly lower pressure than outside air. hope this helps.


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## Ed_GT5000

Here is a link to the other post that reports the same problem:

http://www.tractorforum.com/f166/boiling-fuel-24723


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## wrmdunker

Some good thoughts. I do use E10 fuel and have been for years. I also have a fuel shut-off valve and want to run this again and see if shutting the valve makes a difference. I looked up the boiling point of gas and found many sources to say 100 to 400 degrees depending on the additives so it could be boiling. Or I may be boiling the ethanol. 

Looked at the cap and it appears in tact with rubber innards not showing abnormalities.


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## 2jdeeres

You might want to check to see that you have proper air flow for cooling around your engine.


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## wrmdunker

jd, I have wondered about air flow. You know your tractor after 13 years and it does seems to run hot but I have no explanation for why. The hood and flywheel/blower seal all look good. Wondered if it could be a weak oil pump? It has seemed to be using more oil this year. What else can I check for air flow?


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## 2jdeeres

Check the engine cooling fins and all around, if grass or?? is cloging them it can really raise the temp.


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