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Username Post: Gas cap vented or closed system        (Topic#347047)
Posts: 102
Loc: Minnesota
Reg: 08-24-04
09-08-17 12:19 PM - Post#2707048    

On my '66 El Camino is the gas tank vented?
I'm unable to find a vented gas cap. After a 20-30 mile cruise I open the gas cap and there is a loud hissing and it sounds like someone is banging the gas tank.
Any advise? Thanks

'66 El Camino
'16 Vette coupe
'47 Indian Chief
'53 Linaert carnival ride

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Posts: 1338

Loc: Lake George, NY
Reg: 11-11-15
09-08-17 03:57 PM - Post#2707068    
    In response to cares

If you have no seperate vent off the tank, the cap must be vented.

Posts: 402
Loc: New Braunfels,TX
Reg: 08-16-05
09-29-17 01:35 PM - Post#2709225    
    In response to Shepherd

I had to read your post twice as I thought that I had written it AGAIN. Two years ago, I bought a '68 el Camino with the same unvented gas cap problem. After blowing the membrane in the fuel pump and injecting gasoline into the crankcase, the fuel pump had to be replaced. I solved the "whooshing" problem by drilling 2 small holes in the gas cap to create a vented cap. No problems with pressure build up now. My garage does smell slightly of gas vapors; however, a '55 Chevy in the garage would produce the same aroma. My garage smells like a garage.

Forum Newbie
Posts: 3

Reg: 11-22-17
11-22-17 10:19 AM - Post#2715332    
    In response to larrybrowningmauldin

My '69 Chevelle had a new gas tank installed. The dude didn't uncap the vent tubes. How did I figure this out? I ran out of gas twice, even though the gauge was showing half tank. The suction created such negative pressure that my tank was collapsing, and sticking the gauge at half full. I drilled a small hole in the gas cap and took a compressor to reinflate the tank. Then I uncapped the vent. Then I got divorced and had to sell her. (the car).

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