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Headlamp Vacuum System

PostPosted: Fri Sep 03, 2004 9:44 pm
by bronco
My headlamps on my Elan S4 Sprint, with Non Failsafe units, refuse to pop-up. They move up slightly but not fully even at high revs.

I must have a leak.
I am sure the leak isn't in the front cross-member. (At least I hope not)
It could be in any of the hoses, the operating valve or the vacuum cylinders.
How should I go about detecting the leak? Any suggestions?
Is the operating valve reliable enough?

It could take me hours to track the leak down and lots of money replacing components that don't need replacing. :blink:
Any suggestions would be gratefully received.


Re: Headlamp Vacuum System

PostPosted: Sat Sep 04, 2004 12:55 am
by Fred Talmadge
Check out this Golden Gate Lotus thread <a href='' target='_blank'></a> Also check the engine with a vaccum gauge. Sometimes the first sign of a burnt valve is headlights that won't pop up or stay down, depending on the model.

Fred T. '65 S2

Re: Headlamp Vacuum System

PostPosted: Sat Sep 04, 2004 3:11 am
by type36lotus
If it is not a valve issue as Fred suggests then... If you have a hand vacuum pump you can test the pods individually. If one or both are bad, you have possibly found the problem, there may be more. It is also easy to test the check valve as the check ball could be plugged allowing no movement of air from the tank to create the needed vacuum. The remaining parts are simply tubes and rubber hoses, excepting the control valve on the dash(facia). Also I use cable ties on all vacuum hose connections to assure an air tight connection.

Re: Headlamp Vacuum System

PostPosted: Sun Sep 05, 2004 12:39 pm
by bronco
The problem is sorted.

Thanks for the posts. The GG link was very useful.

Having removed the air filter and ducting for easier access to the vacuum cylinders and cleaning out the non-return valve I fired up the engine and still no luck.
When I stopped the engine I heard a hissing from the right hand side of the engine bay. Eventually, I located it to the hose returning from the switch to the first vacuum cylinder. It had been rubbing against the dynamo and had worn a hole in it.

I taped it up as a temporary repair and the headlights now pop up perfectly.
I will use a cable tie to keep it away from the dynamo.

A simple solution in the end. I am sure there must be a lesson to be learnt here???? :D


Re: Headlamp Vacuum System

PostPosted: Sun Sep 05, 2004 6:21 pm
by Frank Howard

Here's a better way to fix the problem. Get rid of that dynamo and install a small alternator that won't interfere with your vacuum line!

Frank Howard
'71 S4 SE

Re: Headlamp Vacuum System

PostPosted: Tue Sep 07, 2004 9:40 am
by dmreeceuk
I removed my check valve as the spring was broken, the headlights work fine. Do I need a check valve? I dont know why I would because they work fine.

If so where can I get one?
1970 S4

Re: Headlamp Vacuum System

PostPosted: Tue Sep 07, 2004 10:59 am
by Rob_LaMoreaux
Without the check valve the headlights will work until you go up a hill, then with some time at open throttle the vaccume will drop and the headlights will go down (or up with failsafe ones).