From the Lotus Internet List - Dec 1998

QUESTION:
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 #1 intake runner (Dellorto setup, 4 runners) has the vacuum take-off for the headlamp circuit. The lines disappear into the body, so I'm not sure which setup I have (one or two headlamp solenoids). I'll be looking in more detail, soon. I do know that I can hear the air rush when activating headlamps.

The #4 intake runner makes vacuum for the brake booster... that's all. A straight connection, no tees. 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.

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").

I've ordered a valve to restore the other circuit. Hope to get into it all this weekend.

I do appreciate any advice. Thanks.

Cheers from Atlanta,
ken ritchie

RESPONSE #1
From: "Tim Engel" <tengel@isd.net>

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.

There should be a T-fitting threaded into the manifold, then two spigots for the rubber hose vacuum lines. The brake 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.

Oops… Not the brake vacuum line... the headlight vacuum line goes right.

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 "extra" reservoir could be tee'd into that line.

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.

>…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.

RESPONSE #2
From: Mark Hollingsworth <markh@olympus.net>

>My 1975-built Elite has TWO vacuum reservoirs…

The right hand side is for the headlamps, the left hand side one is for the heater/air controls. There should be a 'T' right near where the line comes off of the intake. I can break it down more if you like. The vacuum on the air conditioned cars also controls the water valve for the heater. So if you have a leak, you will not heat any heat.