Hey group

2001 Grand Caravan ES (3.6)
I thought it was the load leveling system but brought my ear up from the rear tire and it was coming from the gas cap. I took the cap off (engine is running) and got a huge rush of air. There was so much pressure in the filler neck (and I assume the gas tank) that it just rushed out. As the engine was idling I left it off for a moment and air kept blowing out of the filler neck.

Is this normal? Just got a new cap to try and fix the P0442 and P0455 issue. Anyone have any ideas?

 

Hey Gang

Bumping this. I was able to video the noise (my wife usually tears out of the driveway too fast to catch it). Any ideas what's going on here?


http://d.pr/v/1iULA

 

I would start with the gas cap. The fuel cap is designed to seal the tank until pressure or vacuum reaches a certain level. It sounds like your positive pressure release valve in the cap is plugged or shot.

 

Dang! It's a brand new cap. I'll put the old one back on and see. Thanks! So there *should* be some pressure like that when it's running?

 

If anything the running engine should create a vacuum effect. I may be wrong but it sounds like the cap is acting like a one way valve. The temp goes down and the tank pulls air in, the temp goes up and the air can't get out. So you replaced the cap and it didn't fix it, or you replaced the cap and the problem started?

 

For emissions reasons the tank is designed to vent through the charcoal canister or engine but the cap will vent if it becomes excessive. You may have a plugged vent line or possibly a bad evap canister or purge valve.

 

Definitely pushing air out.

I replaced the cap and this noise started. Can't say for sure if it was happening before but the noise wasn't happening.

Yeah, I suppose if one of those things is messed up it would also lend to those 442 455 codes.

Will swap back the old cap tomorrow.

 

The codes are bit misleading but make perfect sense. The evap system checks the tank for leaks on a regular basis by applying vacuum to the tank and monitoring the pressure. If there is a leak air gets sucked into the tank and the pressure normalizes. How fast it happens indicates the size of the leak. You don't have a leak. The tests fail because the evap system cannot apply a vacuum to the tank. Why there isn't an excessive pressure code I have no idea.