Headlight pod diping

[triumphelan]

I have just noticed that my drivers side pod dips down whilst at high revs eg overtaking ,it may happen when the foot is taken off accelerator to change up. It returns almost immediately ,the near side stays up .Any thoughts before I start delving into the vacuum system

[steveww]

Looks like a vacuum leak. The usual suspects are the pods or the switch.

To test the pod: disconnect the hose to the pod, raise the headlamp, block the pipe on the pod, let go of the headlamp. Now wait, the pod headlamp should stay up for ever.

[john.p.clegg]

For what it's worth I think it's your non return valve oscillating at high revs,I had the same problem and just fitted another in line with the first and hey presto,just like Viagra they stay up for hours....

John

[MintSprint]

It's a common problem and, as others have said, it is down to a leak in the vacuum system somewhere.

There are lots of possibilities, unfortunately, but non-return valve is a good place to start. Next most likely suspect would be the vacuum switch on the dashboard, but it could also be a corroded, leaky vacuum pod, split/leaky pipes or hose connections or (worst possibility) corrosion of the chassis crossmember.

There's quite a useful discussion on the Golden Gate Lotus Club website:
http://www.gglotus.org/ggtech/elan-hdlamp/headlamp.htm

[RobL7/Elan]

Having just gone through a version of the dredded headlamp dip, I'll offer what worked for me. First apply small hose clamps to all hose junctions. Second if the vacuum pods have small leaks or are suspect, I applied a bicycle tire sealant that flows over the daiaphragm seals the holes, and remains flexable. The stuff in the US is called "Slime" and is a day glow green color!. Finally if the lamps dip mainly on open throttle, the cause is most likely the vacuum check valve. I found that the valve that screws into the manifold has a very low "cracking" pressure. That is the pressure required to open the valve. This low crfacking pressure allows the valve to partially open under open throttle, with the vacuum pressure in the manifold being lower than that required to keep the lights up. The vacuum leaks back into the manifold, and the lights droop. I found a inline check valve with a cracking pressure of 2 to 3 PSI, that seals very good below that "cracking" pressure, that I fit down line from the one way valve that threads into the manifold. Viola! They stay up throttle open or closed. I found the inline valve on line, but they can be had at a variety of companies that deal with vacuum instalations. Hope this helps.

Rob

[type36lotus]

If you don't want to use clamps, quality cable ties work quite well. Are inexpensive, compared to clamps and come in black so they blend in. Get the ones with the stainless steel locking tab, the cheap plastic locking tab ones often pull out. The smaller size works well for small diameter hoses and are hardly noticable. I used these on all my vacuum hose. Especially the one where there the hose connects to a non-barbed fitting... such as the headlight pods.