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Fix your hideaway headlight doors     or just fake it

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Many people have problems with their 1968 / 69 hideaway headlight doors. Few people can describe the entire workings of a hideaway system. I remember seeing no COMPLETE text description anywhere for how they really work in the 1968 shop manual I have.

The best I've seen is little troubleshooting hints from people such as; "check your hoses". Or they'll suggest "this or that" part may be leaking. After you read this article, you'll probably be an expert on them.

I'm pessimistic about hideaways. They seldom work 100%.

Let me recall some of the very silly things people have done to try and keep their hideaway doors up:

(1)  Insert a piece of rubber fuel hose under the door to
     prop it up.   Careful - as this will crack the paint on 
     your Endura bumper if you stress it.
(2)  Insert a spare windshield wiper blade under the door
     channel to prop it up.
(3)  Put a bungee cord in the hideaway door hinge and
     stretch it up into the engine compartment.
(4)  Twist coat hanger wires around the door parts
     and pull them up into the engine compartment and
     hook them onto something.
(5)  New springs.  Forget that.   It ain't ever the springs.
(6)  Magnets, gotta be some way to rig them doors with
     helper magnets.
More seriously, here is your own hideaway vacuum diagram. It comes out of the 1969 Pontiac Service Manual. I have replaced most of the original artist's abbreviations with words you can more easily understand.
Click ->hideaway diagram   hideaway explosionThe second drawing is an exploded view of the mechanical parts. These diagrams may help you with hose connections and parts identification.

Here is my best effort at describing how the whole shebang works.

The hideaway system is a mass of old leaky vacuum hoses (probably 3 freakin miles long). Vacuum is not used to hold the doors in their fully closed position. Overcenter springs do that. The vacuum just makes the doors go past the magic "overcenter" point and the springs hold the doors to the top of their travel.

What's wrong with yours?  Examine your symptoms.
* Doors won't stay closed all the way in their "up" position.  They sag.
If you can push the doors all the way shut with your hand and they won't stay shut, the problem is most likely a mechanical problem, not a vacuum problem.  Check the positioning of the overcenter spring on each side.  The angle of the spring's mounting tabs makes a bunch of difference. A slight rotation of the mounting tab in either direction makes a great deal of difference.  Loosen the tab bolt and move it slightly.  Experiment.  When you get it in the right position, you strike the balance between closing and sagging.  You want closing!
* Doors won't open or close (or do it too slowly).
Problem is most likely in the vacuum system.  And some pivot points may be binding up.

How to positively isolate and test the hoses:
Visually inspect them. Flex them. Look for cracks. Cracks almost always form at the place where the hose fits over a fitting. In some cases, you can cut off the inch of bad hose at the fitting and reconnect the rest of the hose to the fitting. If any of the hideaway system components leak (even a little bit), you will lose vacuum faster. New vacuum hoses may seem like a cheap thing to buy at your local NAPA. But wait! It's a good solution if you maintain a non-stock engine compartment. But it turns out that Pontiac used specially marked vacuum hoses. They run in pairs most everywhere and one of them has a wide green stripe down it. Other sections of vacuum hose have a blue stripe on them. Another specialized part is the dual rubber mating connectors that are used to unplug the hose sections from each other. I've never seen those specialized parts down at the NAPA! If you replace them with generic black hoses and generic- type splice connectors, ok. But it won't look stock. There has got to be a good quick trick for testing hoses to see if they're leaky. Someone fill me in on this.

The vacuum actuators are expensive buggers that sit behind the grilles, just above the front valence panel. The actuators are supposed to mechanically push the doors open or closed. In theory, this contraption should work fine. However, in practice, the actuators are too weak and wimpy to make it operate if there are any vacuum leaks or mechanical hang-ups in the system. A vertical rod sticks up out of each actuator. It doesn't take much rust on the rod to bind it up with the rubber guts of the actuator and make it stick. A little ribbed rubber flexible boot is supposed to keep dust and dirt out of this location. The old boots crack and let dirt and bugs in there. Old vacuum actuators will leak. New vacuum actuators will sometimes leak too.

How to positively isolate and test each vacuum actuator:
Somebody knows and just might email me.

The vacuum cannister is a glorified black coffee can with a hose attached to it. It's big and ugly so they tucked it up under your driver's side fender. Its job is only to hold enough vacuum in reserve to open the hideaway doors a couple times after the engine is shut off. A little white plastic check valve is in the line between the engine's vacuum source and the vacuum cannister. Its job is to stop the vacuum from leaking out of the cannister. Without the check valve, vacuum would leave this cannister like air leaves a balloon if you let go of the untied end. Vacuum cannisters will rust at the seams. The rust will develop into rust holes, allowing precious vacuum to escape. Wheee!

How to positively isolate and test a vacuum cannister:
I hook up a short length of new vacuum hose to it. Keep blowing into it hard till the cannister fills up with air. See if it leaks out the cannister. If your face turns blue, the cannister is probably leaking. Stop blowing before you pass out.

The headlight switch is a special thing. It has a vacuum director valve built into it. When you pull on the knob, the invisible vacuum will either come from the running engine or the vacuum cannister and energize the 2 vacuum actuators behind your bumper. One hose is for "open" and the other is for "close". The hoses make their way to each of the 2 actuators through T-fittings behind the bumper. When you push the headlight knob back in again, the vacuum gets routed to the "close" port on the actuators and closes them if you're lucky.

How to positively isolate and test a vacuum headlight switch:
Who knows? I don't. Someone email me about a good solid test.

The engine. Ahh, the engine is an important part of the mix. It provides the vacuum in the first place. With the engine running, the doors should semi-quickly open and close. When you shut off the engine, the vacuum source stops. But if your check valve is working, you'll still have one "big ugly can full of vacuum" in reserve.  Some sources say that you should be able to make the doors open and close once after the engine is shut off.  That's not really true.  I've never seen a car yet where you could operate the hideaways open and shut with the engine off.  There's just not enough vacuum in reserve to do that.

Pivot points. There are lots of these. Each place where the mechanical door push rods connect, hinge, or scrape, is a place for the hideaway system to break down. Bad pivot points cause friction and binding which can make the doors squeak or be totally inoperable. They sell a black plastic bushing kit. You probably need it to freshen up all the pivot points with it. One of the bushings keeps the rotating horizontal rods from rubbing on the vertical support metal behind the grilles. The old ones always crack and fall out, leaving the horizontal rod resting against a piece of bare metal. Squeak.
Click ->hideaway diagram
Above, a mechanical engineer fixes the hideaway system on Jeff Klein's Illinois GTO in 1993. They still work. There are several other pivot points to look at. There is an E-clip that attaches the actuator rod to the horizontal door rod. Many times a shadetree mechanic will lose the E-clip and throw in a poor substitute connector, such as a tie-wrap or a piece of wire. That's a bad thing. Someone should jump in here and describe the rest of the pivot points and what their weaknesses are.

How to positively isolate and test the pivot points:
A visual inspection is best here. Might want to yank out the grilles so you can get to them. And first pull the flat plastic cover piece between the bumper and the top of the radiator. There will be room enough to get your hand stuck down in there real good. So, always work on the car within yelling distance of the house!

The plastic doors will crack at the edges. Several screws are used to hold the decorative plastic door to the metal door. If the screws are tightened too much, they will crack the edges of the plastic door. Its not unusual to have a hideaway door with half the screw holes cracked off at the edge of the door.
Methods to fix broken plastic door covers:

(1)  Epoxy the broken pieces back together on the backside.
(2)  Secure the door edges using screws with wide black washers around them.
(3)  Look for new door covers on ebay.
(4)  Don't tighten screws till they crack, brute!
(5)  Major GTO parts vendors sell a repair kit.  It consists of flat metal strips that 
     go over the broken door edges.  They hide the cracked edges and give you a place 
     to attach the screws to.
Someone - Please invent an electric motor kit that will replace the whole vacuum door system. Make the electric motor strong. And make it look just like a vacuum actuator. There's a million dollar idea, free.
Updated Sept 2003
Recently, I found a link on the internet where you could buy an electrically motorized hideaway kit. Go to www.tigerefi.com and click on their link for "Products". You'll see a kit that includes an electric motor with connecting rod, brackets to mount motor, brackets to connect the rod to your existing hide-away bracket, electrical wire to run through your existing vacuum line (to keep stock look), control relay, and instruction manual. I have not tried this kit and have seen no reviews of it. A website viewer wrote in September 2003 to say that this company was temporarily out of stock on the motors though!
 
Questions I still have about vacuum headlight systems:
(1) What is the vacuum pressure supposed to be at each point
    in the system while closed / open?   Gee, maybe if we knew
    that, we could start fixing these easier.
(2) How do you isolate and test all the individual components
    in the system?   See my questions about each one, above.
A guy posted a magazine article showing hideaway repairs here...
http://www.goatsgarage.com/flupfrm1.html (Sorry, link was down 10/01)

TOOLS AND PARTS SOURCES FOR HIDEAWAYS
CLICK FOR ANIMATION -> This is the model 06810 Automotive Test Kit. It offers a one-stop resource for the testing of vacuum operated or vacuum related systems on a wide range of vehicles including automobiles, ATV's, boats and even airplanes. This kit tests all vacuum related systems in the engine including ignition systems, carburetors, automatic transmissions, computer systems, fuel systems, air conditioning units, cruise control units, emissions control systems and more. This kit contains the Mityvac® Repairable Vacuum Pump, Automotive Test Adapter Package, 1- 1/4" Rubber Cup Adapter, 24 inches of 1/4" I.D. Tubing and a 110+ page User's Manual. To order, call 1-800-MITYVAC (648-9822)

Good luck, and please add to this topic by emailing me more info or repair tips on hideaways.

VIEWER COMMENTS AND EXPERIENCES:
Received 2/05 - FROM GREG69GTO-"at"-cs.com
I put hideaway headlights on my '69 GTO and had nothing but problems with them sagging and dropping open. As you mentioned, everybody said "check the hoses" or "the actuators are bad" or made some other out-in-the-ozone guesses. I discovered (after SEVERAL attempts at fixing them) the over center spring mounting was the problem. Unless you're very good at aligning everything to within a gnat's butt, the doors will still sag, due to the design. I found by removing the screwed on metal tabs (they're the small metal plates where the top of the over-center spring slips through the hole) and notching them with a Dremel (or other suitable tool) at the top edge (over the existing hole to maintain spring location) you increase the spring tension. It's a little tougher getting the spring on, but hey, the doors stay closed.


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