headlamp vacuum system

[ppnelan]

Andrew, it might be wise to check if the materials it is made from are compatible with petrol, as vapour will find it's way into the pipes - I've heard stories of petrol accumulating in the chassis crossmember...

Matthew

[LoTex]

Well, I have had a chance to look my headlamp vacuum problems this weekend but despite a number of good suggestions I am still at a loss. My system is older than most, I guess, being an S2. It is non-fail safe so the pods always retract once the engine is off. The problem occurs when accelerating, the pods actually dip about 1/3 of the way down then pop back up to full opening, and continue to move up and down as I drive.

The diagram in my owner's manual does not show a Non-return valve, which a number of people have suggested could be the culprit, nor have I been able to find one in the system. Any help on where it might be would be greatly appreciated by this hopeless owner...

Thanks,

LoTex

65 Elan S2

[oldokie]

On my S3, it's in the fitting screwed into the #1 inlet tube.

[RobL7/Elan]

Hi Lo Tex,

I have a 65 S2, and as mentioned earlier in this thread, you MUST have a one way non-return valve after the vacuum outlet from #1 cyl. This non return valve should have a "cracking pressure of between 2 to 4 Lbs. The reason for this, and the most likely reaason for your head light droop, is that under increased throttle conditions, the vacuum pressure drops in the intake system, and will take pressure from the headlight system, unless it is stopped.

If the pressure drops below the 2 to 4 Lb. level the headlamps will droop. Also check the rest of the system from the origin of the vacuum from #1 intake to the vacuum units themselves. Seal everything, use new lines, use smal stainless hose clamps on all connections, check the diaphragms in the vacuum units. If all is well the lights will function in all driving conditions.

Rob
65 S2, 96 Caterham 7