Should I have one in my headlamp vac circuit?
Last design on a +2S/130 (the one with the pull switch operating the solenoid)
Yes you should!
It is the same as an Elan and should be on the front of the inlet manifold part of the cylinder head. It will let the engine suck the air out of the chassis front crossmember, where the ‘vacuum’ is stored ready to suck up the headlight pods when the switch/solenoid is activated.
Do your headlights rise slowly without one?!
Matthew
Guys,
If it is a late +2 the vacuum will pull DOWN the headlidgts because they are failsafe … and yes, you should have a non return valve in the vacuum circuit. It normally comes off No1 inlet port which has a hole drilled and threaded to accept a n/r valve. The usual suspects can supply a new one if needed.
Hamish.
Thanks Matthew,
Yes, my lights raise as soon as I switch off the engine and also raise if I labour the engine even slightly (like going up a hill).
The strange thing is everything was fine when I got the car, just that the crossmember was by-passed, when I bought a T-piece and connected the chassis the problems started. All I can think of is the brass T-shaped pipe fitting I removed had a valve in it although I’d have thought I would have noticed that… 
I checked for leaks everywhere but none seem apparent, can’t hear any hissing either.
Another trip to Matty’s then…
Cheers
More likely the cross member has a leak in it thats why it was bypassed in the first place. If orginal the check valve will be in the tapping into the inlet manifold.
Rohan
hmmm, I didn’t realise it was in the inlet manifold take-off, is there any way of checking this to see if it works?
I was worried it was a leak in the crossmember, but I can’t seem to get the system to work now even by bypassing the tank.
Hamish, you’re right - thanks for the correction! 
Of course, the vacuum sucks the pods DOWN.
Must be the hot weather getting to me… 
Matthew
Matthew,
That’s one of the benefits of living a tad further north (in Scotland). It doesn’t get quite as hot as it does deep in the interior! You guys must be about melting. 
At least it’s a good chance to test your twink’s cooling system.
Hamish.
To test if the check valve present and working OK in its orginal location in the tapping into the manifold.
Disconnect the hose near the manifold and put your finger over the end. Start the engine and the manifold vacuum should pull you finger onto the tube and you should feel this. Shut down the engine. If the check valve is present and working it should hold your finger onto the tube for at least a few seconds with the vacuum trapped between the valve and your finger.
Alternatively unscrew the tube section tapped into the manifold and see if you can look through it or whether there is a valve inside blocking free flow. Test the valve by blowing from each end. You should not be able to blow through the end that screws into the manifold
regards
Rohan
Thanks Rohan, I’ll give it a go.
Rohan,
How long are your arms?
I tried to follow your suggestion and the valve works ok but I have had to make an appointment with my chiropractor!
Chris
Sorry Chris
I should have specified have an assistant start the car unless you find the driving position in an Alfa perfect.
Rohan
Right, I removed and checked the valve - works ok, so I plumbed the pipes up with new tubes bypassing the crossmember. Now it works as it should…
So it would appear I have a leak in the crossmember (Spyder chassis), I have sealed up the drainplug with PTFE tape, sprayed washing-up liquid everywhere and blown into the tank, tried the butane test thing but can’t find any sign of a leak.
Should I worry about this? The chassis looks in good condition as far as I can tell under the black bitumastic coating that was applied during the resto (the guy didn’t like the red colour).
If I should worry about it, does anyone know how much Spyder would charge to fix it? (bit ambiguous I know as it depends what the problem is)
One thing you could try is to fit a tyre valve to it and try pressurising it with tyre weld. Just an idea…