Fuel tank pressure equalization

[petergauthier]

I just started experiencing a boom twice a day when my fuel tanks flex because of expansion or contraction. This is after 4 years of not doing that. I am assuming there is some sort of pressure equalization device on the fuel tanks that should prevent that. Does anyone know how that works? I have a 2019 Cyclone toy hauler with a fuel tank for the generator and a fuel tank for toys.

 

[LBR]

After filling our 2017 CY tanks, I tighten the caps until clicking, then loosen them 3/4 turn to the "stop".

If I don't back them off 3/4 turn, the tanks build up heat soak pressure.....when backed off, the pressure vents A-OK.

 

[david-steph2018]

Same thing, back off the cap a little.

 

[centerline]

its because you have an EPA certified tank cap... which doesnt allow the tank to vent to atmosphere... loosening the cap should prevent the "oil canning" effect from expansion/contraction...

 

[petergauthier]

Thanks for the tips. When I backed off the cap 3/4 turn to the stop it works fine. Now I have to replace one of those caps. Does anyone know where I could get one. A manufacturer and model number would be great. There is neither on my caps and the auto parts places don't seem to be able to find one.