Ford F450 V10 gas cap popping

[ladyrvr66]

What causes the gas cap on my 2007 Coachmen Concord with only 19000 miles to start popping, like it has pressure behind it, after you have driven just a few miles? Thanks so much, as am planning 1000 mile trip in next couple days

Ladyrvr66 & Bubbles

[spider13]

The only thing that will make anything pop,is pressure.Check your vent tube.

[ladyrvr66]

Thanks so much for your reply. By chance do you have an idea of where the vent would be located, so I might check it out myself. THANKS

Ladyrvr66 & Bubbles

[ladyrvr66]

My last question asking where vent is located was silly on my part. I just mentioned this to my son and he said gas cap's are vented. I feel really dumb. Going to check it out now. THANKS SO VERY VERY MUCH

ladyrvr66 and Bubbles (13 year old poodle)

[twinboat]

There is no vent tube. Gas tanks are closed systems so the fumes don't escape to the atmosphere.

There are charcoal canisters and valves and hoses controlling the tank pressure.

If it pops off while driving, make sure it's the right cap.

It should set a Check Engine light, does that work ?

[TeJay]

A bit more info on the vent systems. Twinboat is correct most all systems are sealed. However it's not a simple as that. The EPA regulations apply differently to different vehicles. When the EPA makes regs regarding most emissions they apply it at different times based on the number of vehicles being made and sold in the US.

Since we buy more cars than trucks they apply the regs to cars first and trucks later. I don't know which regs applied to trucks in 2007.

If it's meeting full regs in 2007 as most cars the systems are completely sealed. No gas fumes escape into the atmosphere. They are collected into the charcoal canisters and purged by vacuum at regular intervals. Also the system is checked by applying a vacuum to determine if the system is sealed. That's what was happening when check engine lights came on because owners were not making sure the gas cap was on tight. If the system faile the vacuum test a MIL will come on.

As already stated if something is not allowing fresh air into the tank as gas is used out of the tank and either pressure or vacuum results it should turn on the check engine light. Since we can't hear the popping noise and no MIL (Maintenance Indicator Light) is on you may not be having any problems except a popping noise.

You have 4 choices. 1. Leave it like it is but buy a new gas cap just in case there's any issue with it while on the road. If over time nothing happens take the cap back. 2. Just replace the cap because there's not much else you can fix. 3. An inspection of the vent tube looking for any place where it might be pinched blocking the flow of either air or vacuum. That's not a likely problem unless somebody has done some work in that area or you had a dent or maybe a nest of some sort got built in the vent tube like what happens with AC drain tubes. 4. Take it to a dealer and have them look it over.

The sealed gas system and the gas cap are not high maintenance or things that owners have many problems with at all.

TeJay

[gorwig]

Originally Posted by ladyrvr66

What causes the gas cap on my 2007 Coachmen Concord with only 19000 miles to start popping, like it has pressure behind it, after you have driven just a few miles? Thanks so much, as am planning 1000 mile trip in next couple days

Ladyrvr66 & Bubbles

Almost all modern gas caps have valves that limit the level of pressure or vacuum that can build in the gas tank. If either of those valves fail there will probably be a "check engine" light on the dash that eventually comes on.
Your comment about your gas cap "popping" is not real clear. Do you mean that it actually pops out of the neck of the fill tube and hangs loose? Or does it "pop" a lot of fumes out as you loosen it? Or does it make audible popping sounds as you stand nearby and listen to it?
The first situation is serious and needs immediate attention. Something is really wrong with your gas cap and filler tube if the cap pops off and hangs loose. Get to a repair center right away and have it checked! The second situation may be normal ... pressure does build up as fuel warms up. A little bit of pressure escaping when the cap is turned off is common. A LOT of pressure being released means you need a new cap and maybe some other parts of the vapor fuel management system might need testing. Finally the third situation is similar. Either the vent in the cap is weak and venting what should be normal pressure or you might hear the cap working as it should ... venting out excess pressure and making a popping sound. However, this is still not normal. Under ideal conditions the fuel system should not vent to the atmosphere. In that case I would have the system checked to see why pressure is building beyond normal levels.