Vacuum Tank - Spyder spaceframe chassis

[Matt7c]

Ever since I have had my Elan, it has had a leak in vacuum system which has meant the headlamps start to drop precisely 67 seconds after engine switch off. I have replaced nearly all of the vacuum lines and jubliee clips to no avail...I was beginnning to worry that I may need new vacuum pod thingies. Then I spotted a vacuum tank on ebay and promptly bought it for a tenner, fitted it today and the problem has gone. Clearly, I have a leak in the vacuum tank in the chassis crossmember, although no hole is obvious. I have a Spyder spaceframe, fitted about 18-20 years ago. Anyone else had this snag and can suggest a likely spot for the hole?

[rgh0]

The Spyder spaceframe front chassis member that makes up the vacuum tank is a round tubular section. Unless it has been badly damaged in a crash or due to rust the only possible leak points are the drain plug or the welds at the end where the front suspension towers connect. I would suspect a loose or leaking drain plug. reaseal that. If you still have leak look closely for cracks in the welds at the base of the suspension towers.

Generally the Spyder chassis are much more robust than the original Lotus uits and do not develop weld cracks unless severly abused.

Rohan

[steveww]

I second what Rohan says. Check the drain plug for leaks. Use some PTFE tape to ensure it is air tight.

If you have an air line you and pressure the tank and listen for leaks.

[M100]

>If you have an air line you and pressure the tank and listen for leaks.

But ONLY to a few psi (say 5psi max) though as its not been designed as a pressure vessel.

Forget listening unless you are somewhere *really* quiet or you get someone young with good hearing to help - soapy water will quickly show up any leaks for old farts ;-)

[Matt7c]

Blimey, I hadn't realised that June had gone so quickly. Since posting my request, I've been snowed under and have only checked replies today. Thanks for the responses - I'll be checking it out this week and I'll post the findings/resolution once the job is done.
Matt
PS: thanks M100, but I AM young (honest!).

[chrishewett]

My lights were not staying up very well and would droop as I slowed down. This meant I had to drive very fast in low gears at night on country lanes! If I slowed down I could only see the road 20ft in front of the car. Obviously this could not go on so I converted to the failsafe system. When I removed the vacuum pods they both had rust holes in them so large I cant see how they were working at all! Now I have just one pod which holds the lights down against the pressure of a spring. I cant say the conversion was easy and I started to regret it halfway through but now its done I would recommend it to anyone.
If anyone is considering doing this themself I would be happy sharing my hard gained experience!
Chris

[brassringfarm]

I have also converted my S2 to a failsafe system. It went in quite well and only issue was designing the new wiring for the headlamp relays to work with the new S4 headlamp switch. (My car was a basket case and I never had an original switch for headlamps). Again - glad to help anyone
Paul Zimmerman
65S2

[builder618]

anyone ever used the electric lifts seen in Hot Rod Mags?

[JJDraper]

I'm trespassing here, but nevermind! My +2 has a Spyder chassis (very old, circa 1979) and it has developed cracks in the vacuum reservoir around the lower front wishbone spindles, where they pass through. I confirmed this with a slight (emphasise 'slight') pressurisation of the reservoir and a bit of watered down washing up liquid, an old gas fitter's trick. This shows that the chassis is not immune to fatigue cracks.....As far as I am aware, the car has never been raced, but it has, and continues to cover a lot of miles.

I am now in a quandary, new chassis or weld up the cracks??!!.

Jeremy

PS The headlamps work perfectly well with no reservoir - vacuum units connected direct to the intake take off (non failsafe system...).