Weird Boiling Gas Problem.....

Help Support SkidSteer Forum:

cchardwick

Well-known member
Joined
Jan 25, 2007
Messages
52
Hi, I have 1974 Case 1737 skid steer and I was running it today for about two hours and all of the sudden it stalled like it was running out of gas. It only stalled/sputtered for a second and then ran for about five minutes and stalled again just for a second (and the engine didn't quit when it stalled). This happened more and more frequently until finally the engine stalled and quit running. I thought it ran out of gas but when I opened the gas cap on each tank there was tremendous pressure, and if I let too much pressure out, gas would spray out from under the gas cap. It took me about five minutes to slowly let off the pressure until I could get the caps off without spraying gas all over the place. When I finally got the caps off I noticed that the gas in both tanks was boiling WOW. The gas tanks were both 3/4 full and it isn't a hot day, in fact it's pretty cool outside. I'm pretty sure the gas tank is just a divided split from the hydraulic fluid tank (one tank, two sections), I wonder if the hydraulic fluid got too hot and heated up the gas? I let it cool down and it started up and ran fine (after running rough for a minute or so). Any suggestions on how to correct this problem? I replaced the hydraulic fluid and filter just recently, so I'm assuming it's not from a dirty filter or fluid.
 

Tazza

Administrator
Staff member
Admin
Joined
Dec 7, 2004
Messages
16,697
Did the fuel tanks feel hot at all? it takes a fair amount of heat to make petrol boil. Your fuel caps should be vented to prevent excessive pressure as you have explained. Are you sure the bubbles weren't just vapour? i can't see the hydro fluid being hot enough to cause the fuel to boil.
 

cchardwick

Well-known member
Joined
Jan 25, 2007
Messages
52
Did the fuel tanks feel hot at all? it takes a fair amount of heat to make petrol boil. Your fuel caps should be vented to prevent excessive pressure as you have explained. Are you sure the bubbles weren't just vapour? i can't see the hydro fluid being hot enough to cause the fuel to boil.
Actually I didn't feel the tanks to see how hot they were. I did buy new gas caps that are supposed to be vented. They are supposed to vent fumes but not allow liquids. I guess they are not working properly? I've been reading up on gasoline boiling points and it seems that there is a huge range of boiling temps. I'm using premium unleaded that perhaps has more volitile hydrocarbons. Maybe I can reduce this problem by using a lower octane gasoline? When I looked as the gas in the tank after I finally got the caps off it looked similar to a pan of water at a full rolling boil. It seemed to 'boil' for several minutes. Do you think something could be wrong with the hydraulics that would make the oil get too hot? They hydraulics are working great with no other problems, just one small leak on a bucket lift cylinder.
 

Stephend

Well-known member
Joined
Jan 16, 2007
Messages
60
Actually I didn't feel the tanks to see how hot they were. I did buy new gas caps that are supposed to be vented. They are supposed to vent fumes but not allow liquids. I guess they are not working properly? I've been reading up on gasoline boiling points and it seems that there is a huge range of boiling temps. I'm using premium unleaded that perhaps has more volitile hydrocarbons. Maybe I can reduce this problem by using a lower octane gasoline? When I looked as the gas in the tank after I finally got the caps off it looked similar to a pan of water at a full rolling boil. It seemed to 'boil' for several minutes. Do you think something could be wrong with the hydraulics that would make the oil get too hot? They hydraulics are working great with no other problems, just one small leak on a bucket lift cylinder.
if the cap was not venting properly and increased the pressure then it rasied the boiling point of the liquid in the way that a radiator works. When you removed the cap this lowered the boiling point to normal temperature therefore the boiling effect. Think of boiling water in the mountains it boilers at a lower tempature than 100 C or 212 F.
 

cchardwick

Well-known member
Joined
Jan 25, 2007
Messages
52
if the cap was not venting properly and increased the pressure then it rasied the boiling point of the liquid in the way that a radiator works. When you removed the cap this lowered the boiling point to normal temperature therefore the boiling effect. Think of boiling water in the mountains it boilers at a lower tempature than 100 C or 212 F.
Good point. That brings up something I hadn't thought of.... I live in the mountains at 8700 feet elevation. I'm sure that makes the problem worse because I think water here boils around 80F. I bet if I brought my skidsteer down to the shop in the city at the base of the mountains it's a good bet that they won't be able to reproduce the problem because of the higher bp of the gas down there due to elevation differences. Maybe I need to add some antifreeze to my gas to make it boil at a higher temp LOL. (Just kidding). I wonder if I could add some kind of cooler to my hydraulic fluid system, like a transmission radiator mounted by the radiator fans?
 

Stephend

Well-known member
Joined
Jan 16, 2007
Messages
60
Good point. That brings up something I hadn't thought of.... I live in the mountains at 8700 feet elevation. I'm sure that makes the problem worse because I think water here boils around 80F. I bet if I brought my skidsteer down to the shop in the city at the base of the mountains it's a good bet that they won't be able to reproduce the problem because of the higher bp of the gas down there due to elevation differences. Maybe I need to add some antifreeze to my gas to make it boil at a higher temp LOL. (Just kidding). I wonder if I could add some kind of cooler to my hydraulic fluid system, like a transmission radiator mounted by the radiator fans?
you might just need to put a heat shield around your gas tank similar to what is done on most cars. A shield could lower the temperature of the tank would make a great deal of difference. a 10 degrees differnece would make a great deal of differnce on the boiling of gas.
 

cchardwick

Well-known member
Joined
Jan 25, 2007
Messages
52
you might just need to put a heat shield around your gas tank similar to what is done on most cars. A shield could lower the temperature of the tank would make a great deal of difference. a 10 degrees differnece would make a great deal of differnce on the boiling of gas.
Do you think it could be heat from the engine that is heating it up? I was thinking it was the heat from the hydraulic fluid since they are both in the same divided tank. There are two tanks on the skid steer, one on the left and one on the right, both tanks are divided in two with hydraulic fluid in the front and gas in the back. It's a weird setup.
 

Tazza

Administrator
Staff member
Admin
Joined
Dec 7, 2004
Messages
16,697
Do you think it could be heat from the engine that is heating it up? I was thinking it was the heat from the hydraulic fluid since they are both in the same divided tank. There are two tanks on the skid steer, one on the left and one on the right, both tanks are divided in two with hydraulic fluid in the front and gas in the back. It's a weird setup.
I have heard of this setup and it is indeed odd. It could very be the heat from the engine causing the fuel to boil. I can't see the fact you are using premium fuel to be the problem.
 

sar4937

Member
Joined
Jun 28, 2005
Messages
21
I have heard of this setup and it is indeed odd. It could very be the heat from the engine causing the fuel to boil. I can't see the fact you are using premium fuel to be the problem.
Actually fuel is comprised of many volatile components, some of which start to boil at as little as 160 degrees f. I do not believe that there is an actual boiling point that you can reference. As they boil off they change the makeup of the fuel and how it performs. I would recommend using a meat thermometer an checking the temperature of the liquids. Also there is no advantage to a higher octane rated fuel than what you engine compression ratio can utilize, and premium does have a lower boiling point (rvp). I would worry alittle more about the venting fumes exploding, and the flashpoint of the fuel. If the fuel is soaking up heat from the hydraulic side of the tank you would have to circulate it through a cooler and back into the fuel with some sort of a pump- dangerous! It would be better to know the temperatures involved and fix the source of the heat. I would think that you skidsteer hydraulic system was designed to run cool enough not to boil the fuel in the tank, but it would be easier to cool the hydraulic side rather than the fuel. Keep in mind that when the fuel hits it's flashpoint it will spontaneously combust when air is added. If your fuel system recirculates fuel back to the tank make sure that your fuel lines are not laying against the exhaust system as the heat will be introduced that way. And normally you would be experiencing vapor lock by now if the fuel were boiling because fuel pumps won't pump vapor.
 

Stephend

Well-known member
Joined
Jan 16, 2007
Messages
60
if you need to know the boilng point of gasoline look up the MSDS, Material Safety Data Sheet. Use google and type in MSDS gasoline
 

sar4937

Member
Joined
Jun 28, 2005
Messages
21
if you need to know the boilng point of gasoline look up the MSDS, Material Safety Data Sheet. Use google and type in MSDS gasoline
The actual boiling point of fuel is called RVP and is juggled up and down seasonally. It is hard to pinpoint exactly and will as stated vary with altitude. Flashpoint varies with altitude and humidity. Actually the temps of your other fluids are way more important due to say head cracking if the coolant is that hot, or lubricants breaking down. If you are that curious at what temp your fuel will boil at, you might as well determine what temp you will combust at since you are sitting very close to that fuel that is converting to vapor. The boiling fuel is more likely a symptom of the real problem, and if your hydraulics were so hot as to boil the fuel in an adjacent tank I would expect some very expensive repairs down the road.
 
Top