Lotus Elan

My Elan S2 light pods go down on quick acceleration

PostPost by: loueelotus » Fri Feb 08, 2019 5:40 pm

Hello again Quick question.. At night my Elan S2 light pods go down on quick acceleration.. I heard there are fixes but I have an original car and would like to keep it as original as possible..

As always,
Regards,
Lou
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PostPost by: oldelanman » Fri Feb 08, 2019 6:07 pm

You have a vacuum leak somewhere in the system. Check the Tee piece where the pipes attach to the front cross member that's often the culprit.
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PostPost by: paddy » Fri Feb 08, 2019 6:15 pm

Or just a faulty/missing non-return valve?

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PostPost by: h20hamelan » Sat Feb 09, 2019 3:44 am

A closed throttle will create more vacuum than an open throttle
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PostPost by: Chrispy » Sat Feb 09, 2019 6:20 am

paddy wrote:Or just a faulty/missing non-return valve?

Paddy


This is my guess.
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PostPost by: 69S4 » Sat Feb 09, 2019 7:47 am

Same problem - discovered at 4.00am when I set off for a trip to France last summer.
Same answer - lack of non return valve.

I got one for a few pounds from eBay to tide me over until I can source a good quality one. With the valve the lights stay up for about five minutes with the engine off so there’s obviously a slow leak somewhere else. No1 suspect is the switch /valve which is untouched since 1969.

Last time the lights wouldn’t stay up it was the original plastic T piece. It split in such a way you had to take it off and twist it to see the split. On the car it looked fine.
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PostPost by: loueelotus » Sun Feb 17, 2019 5:49 pm

Thank you all for the info.. I was wondering . How long the average light pods stay in the up position on the own after the Elan S2 is turned off with out any vacuum issues? Also do they make better T connectors to chassis and who would have them ? ( brass etc..)

Much appreciated,

Lou
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PostPost by: billwill » Sun Feb 17, 2019 6:04 pm

Mine only stay up for a minute or so, but I haven't done a thorough search for air leaks.

(Non-safety type... Vacuum lifts the pods.)
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PostPost by: 69S4 » Sun Feb 17, 2019 6:12 pm

There's a macho element to this - my light's stay up longer than your's :lol:
I think there's been a discussion about how long they should stay up in the past - hours comes to mind if there are no leaks. Mine went from seconds to about five minutes after fitting the non return valve

The original T piece on my S4 was plastic with 'female' ends - the black plastic tubes were a push fit inside it but none of those were available when it split some time ago so I used a brass T instead. To link that up though meant using short 'rubber' sections to convert the male ended brass T piece to the needed female ends - and six jubilee clips to hold it all together. It works but it's an unsightly bodge. Whether the original style female plastic T's are now available I don't know.
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PostPost by: loueelotus » Tue Feb 19, 2019 1:50 am

Thanks again for all the info.. My light pods would stay up for several hours in the past but now it seems to be within about an hour (I think).. When I start it this early spring I will check it out if I can not find a leak.. But I received great info so as soon as it warms up a little I will start. the search.

Regards all,
Lou
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PostPost by: JonB » Tue Feb 19, 2019 12:11 pm

Your car is obviously closing its eyes because your rapid acceleration is frightening it. :D
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PostPost by: rgh0 » Tue Feb 19, 2019 12:23 pm

With a tight vacuum system the lights should stay up or down for months.regardless of the engine manifold vacuum

My plus 2 Elan with the fail safe system will hold the lights down for many months when I have had the car off the road for other work without the engine starting.

The failed non return valve or leaks in the actual headlight raising switch valve or a front cross member reservoir leak are the main source of vacuum leaks in the non fail safe system you have on your car and the vacuum stored in the reservoir is insufficient to cover you through a few minutes of low manifold vacuum

cheers
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PostPost by: loueelotus » Tue Feb 19, 2019 3:46 pm

Thanks..Understood.. I have and will recheck carefully the whole system.. So here is the big question.. If visually all seems to check out. Then how do you check the vacuum system? In other words set up a vacuum and watch and listen.. or it there another way?

Cheers,
Lou
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PostPost by: h20hamelan » Tue Feb 19, 2019 4:35 pm

I would use a hand held vacuum pump, or a bycicle pump
If using compressed air, be very very gentle 17-23 Inch
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PostPost by: nmauduit » Tue Feb 19, 2019 6:34 pm

h20hamelan wrote:I would use a hand held vacuum pump, or a bycicle pump
If using compressed air, be very very gentle 17-23 Inch


The chassis vacuum tank alone can be pressure tested for leaks as it'll then isolated (watch out for the presurized gunk that will be spit out when you take the air pressure hose out... been there ... )

to check the whole system for leaks with compressed air (rather than vacuum) the valves (that includes the manual switch) should be removed (or reversed, then do not exceed 14 psi) as they would be passing in that direction - I would rather not go that way and stay with a manual pump or other method (test by section, test with a helper... there are not that many parts in the vacuum system after all).
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