Lotus Elan

Do i have a vacuum leak on my headlamps?

PostPost by: sdenny » Mon Feb 05, 2018 5:45 pm

I have a 1969 +2s. The lights are the "non-failsafe" type and so retract when there's no vacuum.

With the engine running, they are a little sluggish to lift, but stay up fine. However, they retract almost immediately once the engine is stopped (when the dashboard switch is left in the "raised" position). Does that mean i have a leak in the vacuum? I expected that the lights ought to remain raised and sink slowly over a period of time? (much as the failsafe version is supposed to be able to remain down for a period of time)

Does it say in the hand book how they should behave? (i don't have a copy....)

Thanks in advance

Steve
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PostPost by: JonB » Mon Feb 05, 2018 6:19 pm

I think they should go down immediately, if you have turned them off. With the lift switch on, I would expect them to stay up for a while.

The failsafes fitted to mine rise slowly due to tiny leaks in the vacuum system although the manual says they should stay down for 12-24 hours.
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PostPost by: sdenny » Mon Feb 05, 2018 6:35 pm

Yes - that was the logic i used. If the vacuum can keep the failsafe down for 12 hours, I'd expect mine to stay up for a similar amount of time. I guess i'll have to do some more research...
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PostPost by: billwill » Mon Feb 05, 2018 9:03 pm

I wouldn't worry about it, mine has behaved like yours for the last 47 years.

It probably does indicate an air-leak into the vacuum, probably at the dashboard valve/switch, but it doesn't matter much.
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PostPost by: john.p.clegg » Mon Feb 05, 2018 9:11 pm

Steve
You have a vacuum leak , could be anywhere from the inlet runners via the switch and cross member to the vacuum pods..
One step at a time isolate and test.

John :wink:
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PostPost by: gus » Mon Feb 05, 2018 10:06 pm

Is it factory setup?

The stock dash switch is suspect
as is the check valve
and the vacuum pod
and the crossmember
and all the lines

if it has an electric solenoid fitted it might switch off with the car
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PostPost by: Bigbaldybloke » Mon Feb 05, 2018 10:22 pm

With the engine running and the lights up, try to clamp the vacuum line in various places, probably not good to crimp the plastic line, but the sections of rubber connecting hose should be possible to crimp.
Start at the vacuum pod, they rust and can easily become porous. If ok work back towards the dashboard switch and non return valve on the manifold and hope it?s one of these otherwise it points to the front cross member vacuum tank which is the worst case! Mine used to stay up for an hour or so before I converted it to failsafe, then they stayed down for a similar time. They eventually struggled to be pulled down, and that?s when I found I needed a new chassis........
Change is inevitable, except from a vending machine!
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PostPost by: gus » Mon Feb 05, 2018 10:43 pm

With a good solenoid, new actuator, strong check valve, my headlights would stay down for weeks

without using the chassis reservoir
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PostPost by: sdenny » Tue Feb 06, 2018 9:30 am

Thanks for the advice/comments.

I'll have a look over the weekend. Thinking about it I seem to remember being able to hear "air flow" coming from the locality of the switch, so perhaps that's were to start.

I've found the diagram in the workshop manual, and now know what pipe should connect to where, but it's not obvious if the pipe connections are just interference or should be clamped some how. Any comments?

The car has been restored (not by me) but as far as I'm aware is stock. The pods were new on restoration (about 18 months ago) so hopefully it's not them. It's been a while since i looked under the car, but i seem to remember the lines looked new(ish) (but i've only really glanced at them in passing).

If it is the switch, can they be serviced/refurbished? I'm assuming you can't buy new.....
Last edited by sdenny on Tue Feb 06, 2018 9:37 am, edited 1 time in total.
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PostPost by: JimE » Tue Feb 06, 2018 9:33 am

My non failsafe on my Sprint eventually go down after 10-12 hours. But then on my failsafe plus two, they never come up with the engine turned off unless I operate the switch. Don't ask me why! I'd start with the T piece on the chassis which can work lose and work back from there. Jim
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PostPost by: jimj » Tue Feb 06, 2018 10:44 am

I had a similar, but not as bad, situation. Look here towards the end of page 2 for the resolution; lotus-chassis-f36/vacuum-pods-t34444-15.html
I think I`m right in suggesting that if you pull off the 2 tubes going to the switch and join them temporarily with some connector, you`ll see if the switch is at fault. A cracked T piece is the easiest and most likely fault to investigate.
Jim
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PostPost by: john.p.clegg » Tue Feb 06, 2018 12:05 pm

Steve
The pipes are just a push fit,and they only go on the " switch" one way ( the other way is wrong ) , they can be overhauled but only by a qualified bodger.....

John :wink:
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PostPost by: sdenny » Tue Feb 06, 2018 12:19 pm

Thanks Jim,

Very useful link. Also look like i should probably bypass the switch as one of the first things i do
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PostPost by: sdenny » Tue Feb 06, 2018 12:21 pm

john.p.clegg wrote:Steve
The pipes are just a push fit,and they only go on the " switch" one way ( the other way is wrong ) , they can be overhauled but only by a qualified bodger.....

John :wink:


One man's qualified bodger is another's master mechanic :D
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PostPost by: john.p.clegg » Tue Feb 06, 2018 1:17 pm

Thank you

John :wink:
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