Lotus Elan

Headlight Vacuum cylinder - testing off car

PostPost by: mfcole01 » Tue Nov 06, 2018 10:29 pm

Hi members,

I've been offered a headlight vacuum cylinder. Mine has a hole in it. My car is under restoration and I can't test the replacement in situ. Is there a simple way of testing the vacuum cylinder off the car?

Thanks,

Mike
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PostPost by: nmauduit » Tue Nov 06, 2018 10:54 pm

I assume you'er talking about the vacuum pods : there should be a hole in the metallic can on the bottom side, to let the air in and out on the free side of the membrane, the side which is not facing the vacuum of the cross member via the switch.

One way to try them out of the car is to push on the lever and listen to the whoosh sound, then do it while plugging the port and there should be a resistance that stays if no leak.
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PostPost by: Fred Talmadge » Wed Nov 07, 2018 1:03 am

A hand vacuum pump is pretty cheap and would do the trick
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PostPost by: Mick6186 » Wed Nov 07, 2018 8:19 am

I repaired a hole in my vacuum pod by cleaning the rust off and gluing a rubber patch over the hole. I then covered the half with the hole with a couple of layers of fibreglass matting and resin. It now holds a vacuum for weeks and with a good coat of paint looks fine.
You can test the pod by attaching a rubber pipe to the outlet, pull a vacuum with a mitivac or similar and see if it loses the vacuum.
I purchased a good vacuum pump kit cheaply from ebay,
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PostPost by: alan.barker » Wed Nov 07, 2018 8:59 am

I've tested them before by connecting to a Bicycle Pump to put a very low pressure inside.
Then submerge in Bucket of water.
Before anyone says i know they are designed to work with a vacuum . But this is only very low pressure and does no harm :wink:
Quick easy and no special Tools :mrgreen:
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PostPost by: oldelanman » Wed Nov 07, 2018 9:42 am

Here's another suggestion with no tools required...
Push the rod fully in then blank off the vacuum connection(s). Hang the unit up and suspend weight from the rod, if there are no leaks it should support the weight indefinitely. More added weight = higher vacuum created.
img_20181107_091926.jpg and
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PostPost by: Mazzini » Wed Nov 07, 2018 10:08 am

oldelanman wrote:Here's another suggestion with no tools required...
Push the rod fully in then blank off the vacuum connection(s). Hang the unit up and suspend weight from the rod, if there are no leaks it should support the weight indefinitely. More added weight = higher vacuum created.
IMG_20181107_091926.jpg


This years school prize for physics goes to :D
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