Proudly, Sir. I borrow this picture from another online Z forum because I'm having trouble making my camera and my computer play nicely together just now.
The One-Way Valve is mounted on the driver's side of the firewall. It is actually pretty well concealed and I didn't even suspect there was a valve in there until I took the hoses off. I thought the hose was all one piece and just mounted to the firewall with a wide clamp.
Your MasterVac brake booster gets vacuum from the intake manifold. You can follow the black, pre-formed vacuum hose from the brake booster up to the firewall, then down to the intake manifold. Where the hose mounts to the firewall there's a valve hiding in there.
The hose is actually two parts, joined by the One Way Valve. The valve itself is held to the firewall by a wide clamp which completely covers the valve (which is why I didn't see it in the first place). Unscrew the single screw and the hoses and valve will pull away from the firewall.
Pull the two hoses off the valve. You'll notice the valve looks identical on both sides, but it isn't. Close inspection will show you the tube on one side is slightly larger diameter than the other side. The difference is so slight, it's easy to install the valve backward (which had happened on my car). Either end will even fit into either hose convincingly snug. It's a classic "Murphy", and anything which CAN be installed backwards, usually gets that way.
It's important to mount this valve properly, because it only allows air to flow in one direction (hence the name). The air must flow from the MasterVac into the intake manifold when you step on the brake, or you'll get no power brake assist.
The only way I knew which way to install the valve was to try using one end as a balloon and the other end as a straw. Once I knew which way the air flowed thru the valve, I could mount it back on the firewall so the air would flow into the intake manifold. As soon as I did that, the power brakes became fully functional and I about killed myself at the end of the driveway when I stomped on the brake pedal with both feet and nearly put my head thru the windscreen.
I honestly can't tell you which size tube faces left or right on the firewall, and I doubt you'd be able to see the difference just by looking at them (it's that slight). The only way I know of to make sure it's mounted correctly is to take it off and do the balloon/straw test.
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File comment: The elusive One-Way Valve, after you've found it and pried both hoses off. Note that the tubes appear to be the same size; they aren't. One-Way Valve.jpg [ 4.26 KiB | Viewed 3989 times ] |
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File comment: The One-Way Valve is mounted onto the driver's side of the firewall, hiding beneath a wide clamp One-Way Valve, 240Z.jpg [ 254.96 KiB | Viewed 3998 times ] |