700 dragon gas cap issues

[scalded dog]

OK guys;
I have some weird issues with my gas cap on a 2007 dragon 700.
I seem to build excessive pressure in my gas tank.
While taking a break I will hear my gas tank whistling, til I loosen the gas cap then whistling will stop.
This went on for a while til the gas cap started leaking excessively. I got a new cap and the mechanic replaced a check valve near the tank some where, that was last year, now this year the same problem is starting again.
anybody have a similar issue.
Appreciate any info
thanks Jeff

 

[cbrew325]

The gas cap on mine was leaking. I siliconed it around the edge of the clear plastic window where it was leaking. It's been fine since.

 

[ElectroTech]

It is normal to have some pressure in the tank, its limited pretty low by the said check valve, it is no longer open for emmisions sake, it will fling the cap in the air if you give it a quick spin.

 

[scalded dog]

SO is that much pressure normal or necessary
thanks for any help

 

[mtnsledder]

I noticed the same thing on my 07 600 when I first got it. I talked with the service department and they said it was normal.

I've got 4500+ miles on mine now with no problems.

 

[ElectroTech]

Basically only a small amount of pressure, when we were replacing gaskets and doing filler neck repairs on the 900s the tank would swell up alot with only 5 PSI. Almost all new sled whistle or make harmonica noises when you are around them. The pressure is to keep vapours from escaping and destroying everthing cute and cuddly.