Replacing headlamp vacuum hose in dash
I have a 1970 Corvette, and a 1976 Corvette. I restore and customize Corvettes.
So you're getting ready to do the Fun(?) stuff, huh? Yes sir, nothing will make your day more than replacing your vacuum hoses for the headlamps.
I'm going to detail the hoses out, and the parts they connect to. Then I'm going to give you a link, that I feel will show the headlight vacuum diagram in great detail, plus a few tricks from me.
Let's start with the hose that comes from the intake manifold. The main supply of vacuum. It comes from the rear of the intake, and goes over to a Vacuum Filter. The vacuum filter is an item to replace, as it's a possible source for a vacuum leak, and prevents contaminating particles from entering your engine.
From the vacuum filter there is a hose to a Check Valve. (Another item to replace) The check valve then splits into two fittings. Two hoses come off of it. One hose leads into the firewall, and comes up under the dash. It connects to the light switch. The light switch has two fittings on it. One towards the pull knob, one towards the end of the light switch. This hose connects to the fitting at the end of the light switch.
The fitting on the light switch towards the pull knob, has a hose that comes off, and goes to the Pull Down Switch. (Manual Override Pull Down Switch) The little plastic knob you pull to keep the headlights up, or push in, so they the headlights will close when the headlights are turned off.
The other hose that comes off of the Pull Down switch, goes along the left fender well, and ends at the front of the car. It fits into a plastic 'Tee'. The Tee has two hoses coming off of it. One hose goes to the Left headlight Relay Valve. The other hose goes to the Right headlight Relay Valve.
From here the hoses are color coded. You may not be able to see this color code anymore. The color code of these hoses, is Red, Yellow, and Green.
On the Relay Valve it has a vacuum diaphragm chamber. This chamber looks like two pie pans put together. There are three fittings on the Relay Valve body. There is a fitting on the chamber itself. The hose coming from the Tee I described above, goes to the chamber fitting. The other hose coming from the Tee, goes to the other Relay Valve chamber. Doesn't matter which hose from the Tee, goes to what Relay Valve chamber. But when you look at it, you'll know how to lay those hoses out. You don't want then twisted over each other.
The fitting on the Relay Valve that is on the body of the valve, and nearest the chamber, is Red in color. It has a hose that goes to the back of the Actuator. The 90 degree bent metal tube. The actuator looks like two pie pans put together, too. The Actuator has a rod that comes out of the middle of it, and is what actually moves the headlight.
At the end of the Relay Valve body is a fitting. The one furthest away from the chamber. It has a Green hose coming from it. This hose goes to the Actuator on the other side. It connects to a straight fitting, in the middle of the actuator. This is the same for the other side.
The fitting in the middle of the Relay Valve body, has a Yellow hose coming from it. It goes to that long cylindrical tank in the front of the car. At each end of this tank are the bumper brackets.
This hose connects to a fitting at the end of the cylindrical tank. The cylindrical tank is the Vacuum Reservoir. Same thing for the other side.
The last hose is where we left off at the Check Valve. One hose went to the headlight switch. The other hose runs along the fender well, and connects to the Vacuum Reservoir. The long cylindrical tank up front.
Tricks:
1.With vacuum built up, press the rubber seal that's on the shaft (Rod) coming out of the Actuator. If you hear a vacuum leak, the seal is bad. This seal can be replaced without having to replace the Actuator. It isn't easy, but it isn't that tough.
2.With the check valve removed, blow air into the single inlet. If you can blow air through it, this check valve is shot. It's about $14 and should be replaced.
3.If the Vacuum Filter is soiled looking by holding it up into a bright light, and looking at it, it should be replaced.
4.The best method if your budget will allow, is to buy those vacuum hoses as a kit. They are color coded, and come with instructions.
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