Location of one way valve for headlight vacuum line

[Certified Lotus]

Can someone show me a picture of the proper placement of the one way valve that is in-line for the headlight vacuum line.

I have seen it in several locations and wonder which is correct?

Thanks!

[StressCraxx]

Not sure if it's correct, but mine is attached to a short piece of hose connected to the hose fitting on the #1 inlet. From there, its connected to the plastic hose that runs to the crossmember tee fitting.

[CBUEB1771]

Not sure if it's correct, but mine is attached to a short piece of hose connected to the hose fitting on the #1 inlet. From there, its connected to the plastic hose that runs to the crossmember tee fitting.

This is correct, as shown in the appropriate illustrations in the Service Parts List. If you don't have the parts list you can view the on-line version at the RD Enterprises we site.

[billwill]

Not sure if it's correct, but mine is attached to a short piece of hose connected to the hose fitting on the #1 inlet. From there, its connected to the plastic hose that runs to the crossmember tee fitting.

This is correct, as shown in the appropriate illustrations in the Service Parts List. If you don't have the parts list you can view the on-line version at the RD Enterprises we site.

Or indeed on our own site here in the Wiki section under development.

[rgh0]

The parts list shows two types of non return valve before and after unit 8729.

The early non return valve I believe was the one that screwed into the No 1 cylinder inlet. My Elan unit 8555 came with this

The later arrangement after unit 8729 I believe was the one with the non return valve fitted into the rubber hose that came off a plain hose spigot on the no 1 inlet.

As with all changes in Elan parts the unit number for the change is only ever a rough guide at best

cheers
Rohan

[Certified Lotus]

Thanks everyone. I have a plastic one way valve (made in Germany) from RD Enterprises and I have seen them installed in two different locations. One location is near the engine where the vacuum port is located and the other location is near the t-fitting. Which location is better or doesn't it matter?

I was going to install near the t-fitting as I was worried the engine heat would damage the plastic valve after some time.

Your comments are welcome.

One way valve for vacuum line

[rgh0]

I replaced my manifold screwed in one way valve that lost its check ball about 30 years ago with a plastic valve that I mounted near the tee for the same reason. Has worked fine ever since.

cheers
Rohan

[CBUEB1771]

The conventional wisdom is that the non-return valve should be located as close to the inlet manifold as possible. This minimizes the length of hose in which fuel vapor could possibly condense and accumulate over time. Given Rohan's experience it seems that the conventional wisdom is not too important in this case. I found an all-stainless steel non-return valve for threading into the inlet manifold vacuum port many years ago, again no problems since then.

The vacuum port in the #4 inlet tract is used for the brake servo in Elans so equipped. Functionally it would make no difference if you used this port or that for cylinder 1 for headlamp actuation.

I believe Rohan is correct about the non-return valve with hose barbs at both ends being the later of the two configurations. The Elan Service Parts List is not very helpful as only this configuration is illustrated in Plate B11. However the +2 Service Parts List indicates only one non-return valve for all production and the in-hose version is illustrated.

[jimj]

I don`t know about an S1 but on a Sprint it`s this; centre right shiney thing, available from Sue Miller. It screws into the brass "T" piece with the "T" going to the servo. It`s the same on an S3 but without the "T".
Jim

[CBUEB1771]

on a Sprint it`s this; centre right shiney thing, available from Sue Miller. It screws into the brass "T" piece with the "T" going to the servo.

I stand corrected. For some reason I thought that Elans with a brake servo would have had the vacuum plumbing done the same way as the +2. On the +2 the servo vacuum is tapped off of inlet #4 but after double checking it is clear that on the Elan both the servo and headlamp actuation vacuum both come off of inlet #1 via a tee.

[billwill]

The T piece on the vacuum reservoir of my S3 has a non return valve NRV built into it on the carb side.

There is another NRV in the pipe very near the carbs.