air blowing out gas cap vent hole on 656

Don656 · Apr 18, 2012

Hi All!

I was discing with my 656 gas for about 3 hours a couple of weeks ago. When I was finished and shut the tractor off, I could feel some air escaping from the vent hole in the gas cap. I then removed the gas cap, and there was a notable release of pressure. Is this normal or do I have a faulty gas cap? I have the newer style gas cap on it. Thanks.

mkirsch · Apr 18, 2012

Hot tractor in the hot sun, the air in the tank will expand.

If the air was escaping from the gas cap vent, it is doing its job.

Janicholson · Apr 18, 2012

I respectfully disagree with mkirsch.
The heat of operation and sun were in play, but the air had long before been fundamentally purged. The vapor pressure of fuel (todays and yesterdays inclusive) is such that the light fuel components, some of the main components of gasoline, isooctane, butane, ethanol are aromatic compounds, they will vaporize at room temperature. That is why gasoline will evaporate when placed in the open. In the winter, the temperature is low enough that only a few of them evaporate. Winter fuel is formulated with higher volitility Butane to make winter starting possible. Spring gasoline is a problem because it is quite often the winter grade and will fume excessively out the vent. It is wasted fuel in every way. Modern cars have pressure rated tanks and vapor recovery systems to avoid pollution (hydrocarbons) and wasted fuel. Jim

rustred · Apr 18, 2012

i do agree with jim, cause if you can see it venting at the right angle you can see the fumes coming out not air. maybe hold a lighter in that "air" and see what happens. oh no definitly do not try this at home, its for the mythbusters.

Jim Becker · Apr 18, 2012

OK, so Matt wasn't exactly correct when he used the word "air" to describe the foul vapors that are inside every gas tank. However, Don656's question was "Is this normal or do I have a faulty gas cap?" and Matt's reply of "If the air was escaping from the gas cap vent, it is doing its job." is a prerfectly adequate answer to that question.

The useful comment that could have been added is that when the cap is visibly venting, don't take it off. Let the pressure bleed slowly through the vent.

Owen Aaland · Apr 18, 2012

The replacement fuel cap should have two vent holes. That is part of the reason for the change so that the vapors could vent quicker and not build pressure in the tank.

Super-H-Mike · Apr 18, 2012

The fact that it actually built pressure, as indicated by the escape of vapor when you opened the cap, would leave me to believe the cap isnt venting enough. Sure, sun and tractor heat would expand the air and fuel, but the cap shoulda been able to keep up with the venting I would think...

Don656 · Apr 18, 2012

How do you know that it isn't going to build up too much pressure if you just let it bleed off. I thought that the vent hole should have been able to "keep up" and not allow any pressure build up. So, back to my question, Is this normal?

Don656 · Apr 18, 2012

Thanks! That's what I was thinking, too. I'm thinking I'll get a new gas cap.

mkirsch · Apr 18, 2012

Better safe than sorry, unless of course the new cap is faulty.

teddy52food · Apr 18, 2012

No it is not normal. I have a new style cap that must be gummed up & sealed. Tractor only runs a short time & quits from lack of fuel. Open the cap & it does the same. I had to put a new cap on.

pete 23 · Apr 18, 2012

Make sure you have the new double baffled, double vented cap and do not take it off until pressure is gone . This is the whole deal IH got caught up in law suits with. People getting burned or sprayed with gasoline opening a pressueized tank. The 656 was the worst offender and they were tracked religiously for some time. One law suit I know of went through two states to the previous owner, and dealer who traded it in.

When I was at service training at Hickory Hill in about 1969, they had a 656 gas on a dyno. They hooked a tube to the cap of that fuel tank and ran it out side as the gas would literally boil on that tractor. IH added a large chunk of figerglass insulation to later models to reduce the heat to tank. The 560 was baffled much better and it never bothered as much on the 706 either but it was always of some concern. Cost IH a ton of money and reputation.

armand tatro · Apr 18, 2012

A mounted corn picker on a Farmall 400 and you had/have a combination that is equal or worse than the 656! 1963 wqs a hot dry fall and we had gas/vapors squiting 6 in. out of that silley cap. Came in at noon one day to eat dinner and add fuel. Gas was boiling in the tank and would not idle. Left the throttle closed and ate dinner(Yes:then and now dinner is at noon!) Came out and tractor was idleing and no tank pressure. Fueled up and went back to the field. Don't know why we never had a fire that year. The cure was a heat shield in front of the tank and we cut vent holes in the hood to let all that hot air vent up when it got to the heat baffle. By the way I am looking for that tractor. I think a jockey took it from Il. to wi. Armand

truckerlary · Apr 18, 2012

If you go to ihgascap.com they are still honoring the recall. All you have to do is fill out the form with the serial no. of your tractor and send it off. If someone hasn't already sent your serial no. in they'll send you a new cap. Takes about 6 to 8 weeks.

air blowing out gas cap vent hole on 656

Don656

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mkirsch

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Janicholson

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rustred

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Jim Becker

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Owen Aaland

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Super-H-Mike

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Don656

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Don656

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mkirsch

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teddy52food

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pete 23

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armand tatro

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truckerlary

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