Check valve hose near the oil cap, what does that hose do?

[BeatupRolla]

i noticed some cars have the check valve near the oil cap and some dont.. just wondering what this hose does?? mine had a leak in it and wondering if it is important

found a pic that shows the check valve i am talking about, look at the bottom left corner, its a bit orange.. if you can spot it

[90 GP]

Looks like you need a new vac line. The right side of the hose is so tore up I can see where the hose fits on the check valve. The check valve itself isn't likely to leak unless you break where the hose fits on.

[macboy91si]

As I recall that is a vacuum check valve. It only allows vacuum to pass one direction. You should be able to suck through one direction and not the other. Failure of this device is unusual. Just make sure if you replace any vac lines to put in back how it was. Orange (sometimes blue) are usually towards the vac source. Check valves can often be used to prevent vacuum bleed off of diaphragms, like the ones on a carburetor, but still allow it to receive signal from whatever source.

Are you curious about this specific one or just in general. All of the 4AF (carb) motors have one or more of these somewhere or another. The EFI models do not employ them I do not believe.

There should be a vac diagram on the hood and it should tell you where it's going. The other inline device to the right is a delay valve.

-Tim