Headlamp vacuum system

[ditechspain]

I'm just posting this on the off-chance someone recognises the symptoms, so I don't spend hours reinventing a wheel, when I would be better employed sorting out the duff seatbelt reel.

The vacuum system was working fine, usually holding the pods down for the best part of a week. Then, after a few weeks without using her (Elan +2 130/5 big valve), the rear exhaust bobbin failed and the back end of the exhaust dropped down on the road.

After bodging it to get back to the house it became clear that the headlights were now rising on anything near an open throttle, and the lights are now back up within 45 seconds of stopping the engine. I wasn't taking any notice of the lights before the exhaust fell off, so I can't say for certain that they were operating normally immediately before the bobbin failed, and we were only about three miles from the house. However I think I would have noticed if they were coming up, as we go uphill almost immediately.

I'm not familiar with Elans, but from what I can see there's no obvious link between the exhaust and the vacuum system, and nowhere where the systems run close. Before I get it all up in the air and start tracing/checking the system from one end to the other, are there any "usual suspects" I should start with?

Thanks for any advice

[jimj]

Yes, it`s nothing to do with the exhaust. The most likely fault is with the plastic "T" piece. If you look under the front of the car in the centre you will see the chassis cross member has a short pipe sticking out. This is to the vacuum tank inside the chassis member. There should be 2 plastic pipes, one from each side, connected to the "T" piece that fits on to that short metal pipe. Perhaps one of the pipes has come off or the plastic "T" piece has split.
Jim

[alan.barker]

check the "T" piece connection on the Chassis, just below the Rad
Alan

[elansprint71]

If it is not the T piece (usual suspect as advised) maybe the non-return valve (in the pipework, near the manifold take-off) has gummed-up while car was out of use.

[collins_dan]

I am assuming the location of the plastic tubing on the plus 2 is similar to the elan, in that it passes right by the exhaust manifold. I once had a tube get melted by the exhaust manifold and had similar symptoms. The bigger the leak, the greater the impact, so my guess is that something is disconnected, or a big hole in a pipe.
Should be easy to find, just trace from the connection to the manifold. Dan

[vxah]

You also need to check the actual control valve. To get the lights down it seals off the open air port and connects the vacuum servo pod to the vacuum tank, when lifting the lights it seals off the vacuum port from the tank and connects the port from the servo pod to the poen air port and of course the light units go up. When the control valve gets old and dirty they can stick or just not seal off the ports propery so you can have the servo pod connected to both a vacuum supply and open air! When you have a good vacuum from the engine the lights will just about stay down, soon as you lose that, up they come!
I would connect the pipe from the tank to the pipe from the servo pod and see if they stay down for a week?
If not look at the check valve on the manifold?

[ditechspain]

Thanks to everyone who replied to this. Sorry about the delay in a acknowledging, but I only got round to going under the car on Sunday.

As advised in the first two replies, I looked at the "T" connection which was virtually in two pieces. I presume it's the original and the plastic is clearly time expired.

For anyone else faced with the problem, can I recommend for a bodged/improvised repair (my usual standard) some 7mm high-pressure fuse hose and a white plastic "Y" connector, all from the racks at the local Halfords, which re-established the vacuum which is still holding nearly four days later.

Elegant it isn't tho'.