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Dump Truckin SOB
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90 Posts
Discussion Starter #1
My Freightliner fuel cap is leaking fuel from the vent on the cap. I bought a new cap thinking it wouldn't leak. The new cap has a vent also. Well a few miles down the road and its leaking too. So can I get a cap with no vent? Is the vent on the cap a must have?
Thanks
Brian
 

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Highway to Hell
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1,022 Posts
got to have a vent in the fuel tank. it can be on the tank or in the cap but you have to have a way for the tank to breath. not just for the suction of the fuel but for changed in the temps. Its been my luck that vented caps always seam to leak? my hyd tank has a large vent with a hose that runs to the back side of the tank to hide the residue that drips from it.
 

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The other guy
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3,936 Posts
They should stay dry. They're all vented. Just make sure it's not the return line tank that's leaking or it's not the cap (if it just started). If it's a one tanker or the non-drain tank check the seal seat and lip for dings or cracks in the weld. If it's for sure the cap and it's not overfull or under pressure warranty your new cap. ;)
 

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Dump Truckin SOB
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90 Posts
Discussion Starter #5
Yes theres a o-ring on the under side of the cap but I've gotten a new one of those and it still leaks.
 

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Senior Member
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2,555 Posts
The return line is prolly emptying in to the air space above the fuel, creating a vapor cloud, this can be solved by extending the in tank end of the return so that it is under liquid most of the time, a hose with a weight is good, then you can grab it with some thing if you want to observe the fuel return.
Return under fluid has been standard for years in the hydraulic industry, don't know why not in fuel.
 

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The other guy
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3,936 Posts
The return line is prolly emptying in to the air space above the fuel, creating a vapor cloud, this can be solved by extending the in tank end of the return so that it is under liquid most of the time, a hose with a weight is good, then you can grab it with some thing if you want to observe the fuel return.
Return under fluid has been standard for years in the hydraulic industry, don't know why not in fuel.
Good post!! And $$$$ . Them pennys add up ;)
 

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Junior Member
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1,811 Posts
My Freightliner fuel cap is leaking fuel from the vent on the cap. I bought a new cap thinking it wouldn't leak. The new cap has a vent also. Well a few miles down the road and its leaking too. So can I get a cap with no vent? Is the vent on the cap a must have?
Thanks
Brian
FTL's have vents on the top of the tank(s)...probably stopped up, either dirt dobber, or fuel and dust.
 

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Junior Member
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1,811 Posts
The return line is prolly emptying in to the air space above the fuel, creating a vapor cloud, this can be solved by extending the in tank end of the return so that it is under liquid most of the time, a hose with a weight is good, then you can grab it with some thing if you want to observe the fuel return.
Return under fluid has been standard for years in the hydraulic industry, don't know why not in fuel.
KW's still do this...except the vent line is bent away from the suction pipe...to keep bubbles from entering the suction. Not a very good idea.
 

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Junior Member
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16 Posts
Yes theres a o-ring on the under side of the cap but I've gotten a new one of those and it still leaks.
Take a close look at where that o-ring seals on the filler neck,they can get dinged up from the fuel nozzle when you get fuel.
 

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Senior Member
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502 Posts
Take a close look at where that o-ring seals on the filler neck,they can get dinged up from the fuel nozzle when you get fuel.
Right.... The Classic has different tanks than my FLD. Mine doesn't leak but it does. The o-ring goes in the neck on the tank and like you said it gets dinged up pretty good by the fuel nozzle.

My cap is vented not the tank. Can't remember on the Classic but I'm thinking its the same way. I'll look when it gets home.
 
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