Vacuum system (brakes and lights) - 4 articles

(You should also look at the light pod section, as it is related)

Tracking a leak

Before getting too carried away with diagnosis, go for a drive. Get the car up to speed and then take your foot off the gas and coast. Down hill is better. Leave the car in gear and the clutch engaged. Down shift to get the rpm up. In this condition, the engine will be sucking as hard as it can against closed throttle plates and the vacuum will be at it's best. If the headlights don't go down now, you have a strong leak somewhere in the system. If they go down but try to come back up when you slow down or step on the throttle, you still have a leak; but at least you know that the basic system is working.

A leak could occur anywhere in the system. If the hoses are old, they may have become brittle and cracked. Or they may have lost their elasticity such that they don't seal well when pressed onto the metal fittings. It's best to replace all rubber hoses in the vacuum system. Secure them with clamps. The hard plastic pipe is less of an issue, but it does crack if kinked or pinched. Check every inch you can get to.

The solenoid valve(s) (some years used one, some used two) get sticky or won't seal. Whenever the headlights are on/up, the valve is open and un-filtered air is sucked in through the valve along with dirt and moisture. Sometimes dirt collects in the ball-valve seat. Sometimes the steel ball-valve rusts or the plastic seat deteriorates. Any of those scenarios will prevent the valve from shutting off cleanly.

If you are lucky, squirting a little WD-40 into the valve while it's activated and the engine is running will flush it out. If that doesn't work, the valve needs to be removed, dismantled and cleaned. It's not hard to take apart for cleaning. I've had good luck with rebuilding it using steel ball bearings and plastic faucet washers from local hardware stores.

The vacuum non-return valve also gets sticky, but that's only a problem when you want the headlights to stay down after the engine is turned off.

Check the voltage at the terminals of the solenoid switch. If the voltage is low, the solenoid won't be strong enough to operate the plunger valve. Check the ground. In the engine compartment, down low on the right hand wheel well arch opposite the alternator, there is a bolt with a bunch of black (ground/earth) wires clamped under it. The bolt goes through the fiberglass and the chassis suspension support pillar to a nut. This is a,major grounding point and where the solenoid valve is grounded. When (not if) it gets corroded, the ground is poor and the solenoid can't trip the valve. Another good sign that the ground is bad is that the horn gets weak (like meeeerrrp).

The solenoid valve sucks in dirt, the plunger gets sticky and the solenoid can't move it.

.) Disconnect the hose to the headlight and spray WD-40, CRC 3-36, etc. into the hose. If that fails...
2. ) Remove the headlight pod, remove the hose from the valve and spray directly into the valve. If that fails...
3.) Remove the valve, dismantle and clean.

Dave Bean used to sell (still does??) a US made solenoid valve as a replacement. His part number was 75M6200AM. The manufacturer was:

Mead Specialties Company
4114 N Know Avenue
P/N MB 3322S15

I have no idea if they are still around.

Some Elite/ Eclats have one solenoid valve and some have two. A friend's late 1978 Eclat has one valve under the right headlight pod, a "T" fitting and a hose running over to the left headlight. My 1979 has two valves, one under each headlight. Separate vacuum lines run from a "T" fitting at the reservoir to each headlight/ valve. Be sure you check for two valves and clean them both. BTW, his car and mine are only a few serial numbers apart, so the change from one to two valves would have happened somewhere in that time frame. Or they were just inconsistent. Who knows.

Clean the vacuum non-return valve. If it's faulty, a replacement can be purchased from your local Ford dealer. The Motorcraft part number is:


There are two vacuum systems in the car. One for the headlights has the vacuum reservoir in the right hand footwell behind the kick panel. >From the reservoir, the hose goes forward through the foot well and enters the engine compartment through a grommeted hole behind the right wheel well opposite the starter. The vacuum non-return valve is usually spliced into the vacuum line near that grommet on the engine compartment side. Anywhere between the manifold and the reservoir will suffice.

The second vacuum system operates the ventilation system and the reservoir is in the left hand footwell. There should be no connection between the two systems; however, some PO's have been known to "T" them together without using two separate non-return valves.

Trace all the vacuum hoses and connections looking for leaks. This ranks right in there with trying to find an electrical fault. Replace any dried out or cracked hose. Clamp all connections... nylon cable ties will usually do the job.

To check the vacuum pods them selves, purchase a new length of rubber fuel line sufficient to reach directly from the fitting on the front of the manifold to the pod. Connect one pod at a time directly to the manifold, start the engine and let it run for several minutes after the headlamps go down. Place a washer or popsicle stick on either side of the fuel/vacuum line and clamp it off with a locking pliers or C-clamp. Turn off the engine.

This way you have isolated the pod from the rest of the system. You aren't even using the vacuum non-return valve. The only other possible culprit would be the new hose... probably pretty safe. You could use a vacuum pump for this step if you have one. A Mity-Vac will build nice strong forearms before you get a good vacuum on the pod, but go for it.

Let the car sit over night. If the pod is still down after 24 hours, it's okay. If the headlight comes up, the diaphragm inside probably has a small pin-hole leak. Repeat on the second vacuum pod. I have never been able to find a repair kit and new pods are silly-money expensive. After going through my Eclat's vacuum system and making everything right, the headlamps have been very reliable. They will usually stay down 10 days to 2 weeks before they start to wink at you again. Like, "Come on, Big Boy. Drive me".

Noises in the system

On my 1975-built Elite 503 (M100), I had a "clicking" noise, in sync with motor revs. It was diminished when there was some load on the motor. So, I looked for mechanical interference - figuring that as the top end "lifted" a little (torque on motor mounting pads) the movement was relieving the interference. Leaning on something? Nothing. All clear near the firewall and wheel well by the exhaust. Aha! The plastic "non-return" valve built into the vacuum brake booster! Eureka! - vacuum drops under load. Plastic NR valve goes to sleep. In about 5 minutes, I slipped a metal NR valve into the vacuum line just up from the booster, along the firewall. Nice and quiet -- all the time -- now!

Vacuum leak

You should have two vacuum valves, at least the ones I have seen have it that way. You have a leak, most likely in the valve, but it could be anywhere.

Here's how I found mine on my 76 Elite:
Disconnect headlamp hoses, attatch MityVac and 'suck' the lamp down. See if it stays down. Go to the other lamp, same thing. Bypass the vacuum soleniod (hooking the hoses to the lamps) then go back to the air tank in the right hand side footwell. Check there. If no leaks, install the solenoid, see if the leak is gone. If it STILL doesn't leak, then check the air tank, then the line from the oneway valve to the tank, the one way valve etc.

Looking back, it may be easier to start from the other end, just because those are easier to get to.

2 reservoir system

My 1975-built Elite has TWO vacuum reservoirs, one by each footwell. The right hand side (USA passenger) is hooked up to the headlamp pods... and the ventilation flappers (at least I hope so!). It's time to sort them.

The right vacuum reservoir is plumbed into the headlight actuators only. The ventilation system is operated by the vacuum reservoir in the left foot well.

The #1 intake runner (Dellorto setup, 4 runners) has the vacuum take-off for the headlamp circuit.

There should be a T-fitting threaded into the manifold, then two spigots for the rubber hose vacuum lines. The headlight vacuum line goes right and disappears through a grommeted hole in the inner fender in the vicinity of the starter. The ventilation system line goes left over the cams, then forward around the inner fender hump, and does a u-turn to disappear into the double-body cavity. Grope around under the headlight pod and you'll find the opening.

The lines disappear into the body, so I'm not sure which setup I have (one or two headlamp solenoids).

The solenoids are mounted on the front face of the inner fenders below the headlight pods. Use a mirror to look down past the back edge of the pod. If your car has only one solenoid, it will be below the right pod. If it has two solenoids, there will be one below each pod. You can also look into the wheel well. High on the front wall you will see two small (1/4 inch ??) hex heads of the mounting fasteners.

The #4 intake runner makes vacuum for the brake booster... that's all. Straight connection. No tees.

That's right.

I am thinking that the "extra" reservoir could be tee'd into that line. Then the booster would be usable much longer after the engine has stopped.

I've seen some cars where owners have done that. I'm not sure that really gets you much. For the rare (hopefully) occassions where you are stopping the car with the car off, the brakes will still work. It just takes more effort. The brakes are a primary safety system. On the other hand, I wouldn't want to loose braking power because something went wrong in the ventilation system.

What I don't know just yet is how well the flappers will work. I disconnected the headlamp circuit as a leaky headlamp dashpot might lean out #1 mix. Since the NR valve was therefore not being used, I moved it elsewhere... put it in series with the brake booster, to quiet the one-way check valve built into the booster (which tended to "click").

The click happens with the Dellorto's. With Strombergs, there are two intake manifold runners feeding vacuum to the brake booster (servo). With Dellorto's, there's only one runner and the pulses are spaced out much more. Someone told me that if the brake's one-way check valve is functioning properly you shouldn't hear a click. I've replace the valves in my Eclat and Esprit several times and they both continue to click. I haven't tried the redundant valve set-up.

If there's any real benefit to plumbing the vent vacuum reservoir into the brake system, it would be to provide a move steady vacuum supply to the brakes. That should eliminate the click. However, I still don't think I'd do that because of the potential loss of brake boost if there is a failure in the vent system.

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