sshort67

Wife and I are following Route 66 from Springfield, Mo to Santa Monica. Currently spending the night in a Wigwam Teepee in Holbrook, Az. For the past few days I observed a significant whishh (vacuum?) when removing the gas cap. This morning I blew into the bottom side of the cap where the hole is, air went through, on the last fill up no whishh sound. Since the cap indicates "vented" and the sound upon opening it causes me concern. Should I be concerned?

zwede

I had the same problem when the cap was too tight on the filler neck. On the underside you have a plate with a spring behind it. When you tighten the cap that plate goes against the filler neck pushed by the spring. My cap closed tight enough that the spring bottomed out. I think this blocked the vent.

The shell of the cap has 3 areas around the edge that are bent in/up. I straightened them a little using pliers so it didn't go on quite as tight and since then there has been no whooshing.

flyeri

As you probably found it took a pretty stiff puff to blow air out, but if you inhale over the hole air should flow in more freely and you will get gas breath.

The vented cap, when working properly, should let air in as the tank empties so that the tank does not collapse. It also, if working properly, will vent if the pressure inside rises a couple of psi to keep from popping a seam. The way my fuel system is plumbed my pressure gauge will show between 1-2 psi after shutdown when out driving on a warm/hot day, especially when I fill up and run down to 1/4-1/2 tank. If I open the gas cap I get a whoosh and then the gauge reads 0. I have to assume that 1-2 psi is safe for the integrity of the tank or it would have been set to vent at a lower psi.

sshort67

Thanks for the quick reply, both of you.

Rescue Rogers

probably just some dirt. If it were a problem you would have gotten a sensation of no gas getting to the engine. I had that issue on a motorcycle when I was a kid, i just had to open the tank every so often. If it persists go to a shop and blow a little air though it with an air hose or replace it. No danger to the engine.

MelWff

the 1969 gas tank in addition to a vented cap has a secondary valve on the top surface of the tank towards the drivers side of the neck. Remove the gas door and the rubber apron around the neck and try to see if the valve is blocked by dirt. That valve can also fail.

gleninsandiego

I had the same problem. I gently poked the center hole in the cap with a very small screwdriver and got it working again

Glenn in San Diego

OldCarBum

I purchased a new cap from Napa Auto Parts. They were cheap so I bought two.
The fuel caps that Napa sells are manufactured by STAT who were the manufactures of the OEM caps for Corvette.
You can find them on line at Napa Auto Parts and they will locate one for you and get it to the Napa Auto Parts store nearest to your location.
They make the same cap in non-vented as well so just be careful and stipulate that you need the vented cap for your year.
Welcome to California.

sshort67

Good idea. Thanks Rescue Rogers, MelWff, and gwgwgw. No vacuum for the last fill-ups. We have stopped at Neddles, Ca. for the night, an early stop for the night but it is 106. The car was slightly under gauge 210 degrees but my temperature was close to max. Will start in the cool of the morning.

OldCarBum

Cool.
Looks like its been a nice trip.
Several others have shared their Route 66 photos on the forum and its always interesting.
If you get the chance start a thread, post your photos and some of your experiences.
Neptunes Net is a local open air seafood hangout in Malibu, but one of my favorite spots is a little know spot called Paradise Cove Beach Cafe which is a dinning experience all in itself. Both are along the shore on Hwy 101 in Malibu, CA.