I'm chasing an audible vacuum leak near the font of the car. The headlights were operating as they should but thought I would replace all of the vacuum lines, check valve, filter and both vacuum relays since they are 40 years old. I did not replace the lines to the headlight switch or the bypass. Now I start the car and the headlights both go up and then come right back down. They operate correctly using the headlight switch and bypass valve. I read posts suggesting a check valve problem but the headlights operate the same with either check valve. I ran a hose from the check valve directly to the splitter going to the top of the vacuum relays and the same thing happens. Up then down immediately. I am thinking that the spools in the vacuum relays are slow to react. Maybe they have some lubricant or sealant that makes them slide slow enough to build vacuum on the up side until the spool moves and the lights go down and stay there, I checked all lines and they are going to the right places. Has anyone seen this behavior? If the spool are sticky with they work in?

 

Yep.........discribed the problem well.

Here's what helped me....

I grabbed the air hose from the compressor in the barn.
Hooked one end to the pickup at the power brake hose.
the other at where ever I wanted to start listening for a leak on the car.

Boy it wasn't 2 seconds before That suck was heard since the cars engine wasn't running.
Just the trucks.

Just for fun, I tested the servo's independently.
Looking for a weak one.

All came down to that seal in the h-lite servo.
Seem to be where all the action is.

Make sure it's covered by the witches hat's cover too.
It's all Chinese rubber now a days.

Hope that's what there military use too.................










keep looking up and smiling.

 

it takes vacuum to hold the relay in the headlight closed position. no vacuum at the control side of the relay and the headlights rise. i think the aftemarket relays have a too-stiff sprig. so it takes more vacuum to pull the relay to the closed position than it does to pull the headlights up. so you start the car and vac starts to come up. relay is released so vacuum goes to the "open headlights" side. lights go up. vacuum rises. pulls relay to "close headlights" and they close. i am not sure if the relays use the vacuum tank or not. if they do, a vac leak at the tank could be the cause. or a one-way valve no longer holding so it lets tank and system vac bleed off.

 

Lots of years ago, wife and I are at a red light waiting.
Here comes a kindergarten class of 20 or so, all holding hands as they cross in front of our shiny red stingray.

Likey none had seen cars like this except on TV.

Just as the group crosses in front of us, I flip up the head lights to there amazement.
Eyes wide open, they all screem in unison.......''Transformer''.

We still crack up about that to this day.












Pic's of wife on the cover of sports illustrated.
Yeah......that's her.

keep looking up and smiling.

 

If you have not done so you might also want to check your inline vacuum filter and check valve. If the filter is clogged you will not get enough vacuum to hold the lights closed. If the check valve is not holding the vacuum when the engine is turned off and lights pop up until enough pressure is built up. I've experienced both go bad and display the same symptoms. I keep spares on hand. Filter clogged and not enough vacuum will cause it., I even tried to clean mine but did not work until I replaced it. You can check the filter by blowing through to see if there is resistance or remove it from inline temporarily to test as well. As far as the check valve if you have a Mighty-Vac you can check it also.

Good luck, chasing down vacuum leaks is not fun, but once you find them and fix it is gratifying not to keep winking as you drive down the road. :-)

 

Go to your favorite auto parts box store and buy a set of vacuum caps of various sizes. You an then isolate the circuit with the leak. You can also hold a piece of vacuum tube to your ear and use it to listen for a leak source. Just don't drive around without a brake booster, and your car may not like idling without vacuum advance.

Good luck!

 

Since installing new relays the vacuum leak near the front of the car is now gone and the system holds vacuum longer than it ever has. It would normally dump all vacuum within 4-5 seconds. I'm using a vacuum pump used for A/C service and that makes the headlight diagnostics much easier. I attached the pump at the check valve and switch it on with the headlight switch in the off position. I watch the spools for each relay start to move as vacuum builds. It appears that the vacuum reservoir side builds faster than the switching side so headlights go up momentarily and then the spools fully move into headlight down position. Headlight come back down. I could see that there was grease on the spools and they have a bit of stick slip when I push on them with a screwdriver. I cleaned them up with a cotton swab and continued to actuate them hoping they would free up. It seemed to get a little better. Now the lights only come up an inch or so. I can still hear something suspicious near or inside of the firewall near the trans tunnel. There is a branch off the switch side of the vacuum line probably related to the climate control. I'm going to try to isolate that and see if I get a faster reaction on the relay spools. Thank you all for the responses.

 

it takes more vacuum to move the aftermarket spools in the relays than it does to raise the headlights. great big diaphragm in the actuators. smaller one with a spring to move the spool the other way instead of vac in opposite direction. so the smaller diaphrgm has to overcome spring tension before it moves to close-the-headlights position. i think it is going to stay this way unless you get another set of relays and tear them apart, which is a PITA and put weaker springs in them. and the headlights may open on their own after shutting the car off as the vacuum drops. the relay springs will move the spools to open with the lower vacuum but there may still be enough to open the lights.

 

Are you saying it takes vacuum to keep lights down or to keep vacuum relay in lights down position? I just went through the failing vac relay thing a week ago and wound up just changing both relays out. Lights snap up and down with authority now! When I was under the car I pulled all the vacuum lines off both relays as I changed them out and neither headlight moved from the down position. Isn't it the big springs on the headlight actuators that holds the lights in their current position (either up or down) until vacuum pressure from the relay commands the actuator to move opposite to it's current position?

 

Kinda sorta both...
Try this...
Engine running, Headlight Switch in the pushed in or off position
Now try to lift a headlight door and manually lock it in the up position...
I'm not sure you can overpower the energy to the headlight actuator from the closed to open position...
Now, Engine Off, Headlight Switch still in the off position
Manually lift a headlight door and listen for "energy" (I won't call it vacuum) escaping or exhausting from the headlight relay...
Anytime the headlight actuator changes state it needs a path to exhaust that trapped energy...

 

as motojoe said. when engine is running or vac reservoir has residual vacuum, the relays will route vacuum to whichever side-up or down-the relays are set at. here is no shut-off for vacuum to the actuators. they are either being sucked up or down all the time. if vacuum were shut off, they would stay where they are. they are designed to not move until vacuum hits the other side of the diaphragm. the relay is different. it uses vacuum to stay held in the lights-down position sending vac to the lower-the-lights side. when headlights go on or override switch closed, or vacuum leak makes the switch non-functional it is an OFF switch for vac to the relays. then spring tension pulls the relays into the raise-the-lights position and switches which side of the actuator gets vacuum. and this is why the lights will pop up and close when you start the car. vacuum starts to build. relay has not enough to pull spool so the spring says stay open. it doesn't take much vac to move the lights. i can unhook the hoses and raise or lower 1 light by sucking on the hose. human lungs only create about 2 inches of vacuum. so the relay is held open by the springs and vacuum starts to raise the lights. vac comes up and pulls relay closed. lights go back down. people step on the gas and lights go up. that is the one-way valve malfunction so the intake manifold creates a big vacuum leak and opens the relay.

 

Yea, the new import relays are a crap shoot.
Most likely slow to react because of a sticky spool, I like you used the Term "Spool" as that is exactly what it is...
The more you use them I believe they will free up.
Anytime the "Spool" is in between fully UP or in it's Home Position (extended) the relay will port to exhaust...