I did my intake manifolds gaskets a month or so ago . Now while cruising the lights pop up on their own. Obviously a vacuum leak. Not sure where to look but a forum member suggested I clean up my engine bay of vacuum lines since I have no emissions with headers.

Any Idea on the lights? And if someone can mark which hoses i can eliminate that would be great.

 

Since it's both headlights, I'm thinking it's the lines from the engine to the vacuum tank.

I'm pretty sure that even on later C3s the headlights only get their vacuum from the counter-clockwise routed hose in the yellow square, connected to the manifold T-fitting. Make sure every connection at this T is secure. Go to the front crossmember/vacuum tank below the radiator and make sure connections there are snug. A common suggestion is to cut off about an inch of hose to get an unstretched section on the fittings. If all seems good, trace the vacuum line from the tank back to the engine.

 

Can't find any leaks but I did unplug this Check valve. while car was running Lights immediately went down. I plugged it back in and it operates normal for a while then repeats. So bad check valve. I also notice as the lights come up as valve sticks the vents lose all air blowing out.as I'm driving.
I assume this is the problem...

So what is this check valve actually called so I can order it?

 

So it appears this is failing...

 

Here's a link.
It's the first item.
The second says check valve too but that's the white plastic filter.
Good luck!
Regards...

https://www.zip-corvette.com/instant...?q=check+valve

 

Before you buy anything, cut 3/4 of an inch off of each end of all your vacuum lines, a simple loose hose can do it especially at the tee nearest the actuator relay....do your lights stay down at idle and under cruise and come up when you accelerate? Acceleration is when you have the least amount of vacuum to compensate for a leak. The check valve is a good idea, could be a loose hose or maybe you forgot one as well. But them going up could be a leaking headlight switch as well. if you have a vacuum pump you can start at the actuator tee pulling a vacuum there and work your way back towards the tee at the carburetor...if its fine at the headlights and bad at the firewall them its under your dash

A quick tutorial, headlights and wiper doors have two vacuum sources going to them. They tee at the check valve. One line goes to your headlight switch and wiper door solenoid if your car came so equiped. Also in that circuit is the door override plungers these hoses continue to the actuator vacuum relay valve and plugs into the top of it. Most cars except 68s have 2 of these actuator relays, one for each headlight and are teed between the headlights. This applies vacuum to hold a spring loaded plunger up that goes to the closed side of the actuator. Releasing vacuum releases the plunger which applies vacuum to the open side of the actuator. If the headlights are slow openning then i would be more inclined to think it may involve the vacuum tank. The tank hold the vacuum that makes the doors go up and down. No or little tank vacuum causes winking headlights or slow movement

 

I run a aftermarket check valve before the factory replacement check valve, because these restoration quality replacement check valves don't hold. And all is good..

 

And on a 80 model. There is but one vacuum source for both HVAC and headlights. Headlights popping up when vacuum drops is a bad check valve or a leaking vacuum tank.

 

I ordered one from Ecklers before i saw your comment on an aftermarket one. Makes sense why the air blowing out of the vents stopped why the headlights popped up. . It's 95* here. More parts are failing.

 

I run the reproduction check valve for the spliter mainly. And a good quality check valve between the filter and the reproduction check valve. I can open my headlights hours after I shut down the car. It holds that well.

 

Oh, and Ecklers is most likely the worst place possible to order parts from. Read the reviews.

 

Here's my set-up that actually works.

 

Where can I get that brass check valve?

 

Have you considered one of those eBay $100 electric conversion kits. They work a way better and more reliable than the vacuum system and eliminates 23 feet of vacuum hoses and other troublesome components.

 

I bought 2 of em from a hot rod shop here in Australia. I would think a vacuum check valve, Summit racing, Jeggs, your local hot rod shop, eBay, Amazon, etc.

 

I'll look again, all I seen was plastic ones.

 

Hello,
The replacement check-valves are metal and the filters are plastic. Readily available and easy to confuse the two
Check valve.... 1 hose in and 2 hoses out.
Filter...1 hose in and 1 hose out. Direction doesn't matter.
ZIP shows and describes them.
Regards......

Being that you appear to be in N.C. if you order them one day you'll probably have them the next.

 

I forgot and ordered from Eckers because it was the first to pop up. Yes I understand but I want to get the brass one as described . by 4-vettes