Hideaway Headlights Coming Up

The first day I had my '69 my friend and I were checking her out. We put the headlights up, then they wouldn’t come back down. We traced all of the vacuum lines, pulled them off and reset them. I eventually found a pinched and torn vacuum line on the intake. The headlights are only staying down about an hour after the engine is shutoff now.

I called the previous owner last night he said the lights stayed down for about a week before they started coming up. He said he’s heard to take the vacuum lines off, rub a little white lithium grease on the male end of the fitting to help create a seal. To me I would think this would be even less reliable and make the hose prone to slipping off. Has anyone done this or have any tips or recommendations on what I can do to get the headlights to hold down again for a week like he said they did?

If the hoses and fittings are okay, your most likely culprits are the vacuum actuator, or the vacuum storage tank under the LH fender.

You can test the actuator by disconnecting the hoses and linkage, and plugging one of the “nipples” (I forget if it matters which one, but you’ll figure it out) with either your thumb or a rubber cap. Push down on the actuator rod. It shouldn’t move. If you’re able to push it down, your actuator has a bad diaphragm. Sometimes good used ones are available, or you can convert to electric.

The best way to test the vacuum storage tank is if you have a “mityvac” test pump to hook up to it and see if it holds vacuum. Or you could maybe take it off the car, dunk it in water and try to blow compressed air into it & look for bubbles. But I don’t like the idea of getting water in it.

The plastic fittings can be brittle, also check the shutoff valve.

Hope that helps!

I guess the hoses and fittings are ok, they look ok and prior to my experience this weekend he said the covers stayed down for a week at a time. How long and how much vacuum should the vacuum storage tank hold? It definitely holding some now because the light covers don’t immediately come on after the engine is shut off. I don’t like the idea of pulling it off and submerging in water, but I do see how it would be good for testing purposes. I might try the diaphragm test first, but I don’t see how it could have went from holding the headlights down for a week to not even a few hours within a week. Is there any need or anyway to put some type of sealer or anything on the vacuum fittings as the previous owner recommended?

We were messing around with the shutoff valve, but he said he used to do this all the time to show people how the covers went up and down. Is there anyway to check this?

Good advice.Don’t forget to listen closely at the headlight switch for a vacuum leak there. This with the engine off as it will be easier to hear a leak.

Good point about the headlight switch, I’m not sure if I had those lines off when I was trying to diagnose the problem, but I will take a look at them and make sure they are on there tight. The headlights go up very slowly, probably after 3 hours, do you think I would be able to hear the vacuum leak since they go up that slow?

You just might be able to hear a slow leak. No 2 cars are going to be exactly the same. As for the actuator below the grille, look at the rubber boot that covers the actuating rod. There’s a really tiny hole in boot to let air escape so I’m told. Tough to do but try spraying lithium grease in there to seal a possible leak inside under that boot. Always do the cheapest/easiest thing first.

Another possible failure point is the check valve. You can easily pull it out to test it. West Coast Cougar sells a replacement (not cheap at over $50, but they lifetime guarantee it): http://www2.cougarpartscatalog.com/Ford_Mercury_Check_Valve.html?attribs=79
They include a nice write-up that says how to test it: “A simple yet effective way to test your vacuum check valve it to place the single port between your lips. You should be able to freely breath in, but not blow out even the slightest amount. This little valve is responsible for holding all the stored vacuum in the system.”
Original factory spec was 18 hours before headlights start to come up. Less than that, Ford covered repairing the system if still under the original warranty. I changed the headlight switch and check valve last year and trimmed a few of the hose ends by about 1/2 inch each to make them fit tighter, and got it up from 5 hours to about 40 hours. Still using original hoses & actuator (I’m original owner with complete records).

I’m not sure if I know where the check valve is, can you tell me where it’s located at? Thanks for telling me how to test once I am able to find it.

Very interesting that factory spec when brand new was only 18 hours and they wouldn’t warranty any less than that. I’ve read several times people say to cut off 1/2" of the lines for a better fit, I might try that. Should I cut 1/2" off of every vacuum connection that is used for the headlights?

The previous owner mentioned applying some white lithium grease to the vacuum fittings, I was doing some research on the web, saw someone else mention vacuum grease, I googled vacuum grease and found this that I was thinking of getting http://www.skygeek.com/dow-corning-976v-high-vacuum-grease-silicone-5-3-oz.html?utm_source=googlebase&utm_medium=shoppingengine&utm_content=dow-corning-976v-high-vacuum-grease-silicone-5-3-oz&utm_campaign=froogle&gclid=CjwKCAjw8IXMBRB8EiwAg9fgMGmBhECdwMkFHOjnF-OnKxR8KP1NHNnn3bywZH6Z-f9LlA8nuCsTxhoCTKwQAvD_BwE

You can also grease the shaft of the actuator by cutting off the zip tie that holds the accordion dust boot in place. Cutting a little off the hoses can improve the seal at the nipples. Another thing you can do is lessen the spring tension on the doors by removing the spring from the factory position and rotating it to the mount bolt protruding close by. The check valve is on the firewall right of center.


What type of grease should be used on the actuator shaft? Will this help the headlights stay down longer? I read where one guy said to take the spring off, another guy did it, but said it didn’t help and actually put his back on, maybe he should have done as you suggested and just changed it’s mounting position.

I will first check the check valve now that I know where it’s located; thanks for that! Then I will cut a 1/2" off all the vacuum hose connections points in the system and if none of that fixes it I guess I can try the spring.

Droptop, there are 12 places where the hoses fit onto something to do with the function of headlight doors, manifold 1, check valve 3, headlight switch 3, manual valve 2, vac. tank 1and vac. motor 2. I think you will find your leak will be check valve or vac motor. This is after you check hoses for cracks or splits. Oh another thing, if you buy that vacuum pump for AC, you can use that to check your vac.system, just get a gauge and put it in the line coming from pump to whatever you are checking.

I’m going to start off with the lines at the vacuum motor because I had those on and off as well as the one into the vacuum tank. Good idea on using the A/C vacuum pump to test the system! I will also test the the check valve. Once I find something I will update this thread. Thanks for the info!

Very good advice - my eyelids now work great since then as they never open (even when standing for weeks) and work perfectly well when lights are turned on.

Last night I was checking out the headlights and A/C system (separate thread), I cut 1/2" off of the two vacuum lines that go into the vacuum motor and I experimented around with the spring. The lights will definitely stay down with the springs moved, but I’m going to try and get the factory configuration with the springs in their factory position before I move the spring.

This morning I went to the garage, took a look, and the headlight doors were up so I will do the vacuum tank next; I’m first doing the lines I had off first when we were trying to diagnose the problem last weekend and next will be to trim the vacuum lines that go into the headlight switch. After I do all of the lines we had off I will inspect the check valve as I was instructed to do.

Once you trim the hoses, you might try to use small wire ties to clamp them tight.

Not a bad idea, I will probably trim them then if I still don’t get good results I will go back through and zip tie them, but the two I did last night were extremely tight pushing back on after I trimmed them.

Another thing you can do is lessen the spring tension on the doors by removing the spring from the factory position and rotating it to the mount bolt protruding close by.

Where is this protruding bolt you speak of, I can’t find one on my 69

In fact I added a new screw that is longer and closer to the original spring holder so it holds the spring tighter than the screw that Don recommended (the one right in front of the new screw - see pic).

I trimmed 1/2" off of the three vacuum lines that go on the headlight switch, headlight covers were up this morning :frowning: I have trimmed all of the vacuum lines that we had off last weekend so I guess next is to test the check valve and trim the vacuum lines at the on/off switch on the shock tower.

Thank you for the picture, I just looked at my 69 and there are no bolts or screws that the spring could be hooked to, my headlight support and grill piece is all made together not bolted like the one in picture must be a 69/70 thing.