Lotus Elan and Lotus Elan Plus 2 Forums

Note the 3 year recommended service intervals…

Hi Iain,
Page 6A 2b is missing, can you send it please.
Keith

Hi Keith,

I never found anyone that has that page, but you can understand the operation without it.

I have another pdf I found that should fill in any knowledge gaps, the Mk2A works in a similar way...
http://www.hitchhiker.org/fiat/references/Booster%20Rebuild%20Manual.pdf

Iain

Just started to diagnose the problems. Definitely a vacuum problem within the servo. I disconnected the hose at the engine & sealed the opening, engine ran fine, reconnected the hose & the engine rpm's rose. Clamped the hose near the servo & the engine ran fine again with out any increase in the rpm's. I'm now waiting for my wife to return so I can do more checks.

I took the cover off the air valve assy. & when the brake pedal was depressed the valve assembly appears to work correctly. I replaced the cover & then blocked off the air intake, ran the engine & pressed the brake pedal, the engine revs stayed the same. This all points to me to be a leak in the diaphragm or am I missing something? Looking at the diagrams I can't see anywhere else that the air could be coming from.

Yes, I think the same…

Are you saying that the engine revs rise when the brake is pressed or all the time unless the servo pipe is blocked off?

Hi

To me it looks like the control piston and air vales are not working correctly, the air valves must seal correctly you should remove them and check their condition. These seals are avaible from "Northwest classics" on the the net.


good luck

Hi John,

you could be correct, if the air valves were not seating it could allow air into the vacuum side of the diaphragm, and back into the inlet manifold. A punctured diaphragm would have the same symptoms.

if anyone is interested - for £5 on eBay you can buy several Girling service manuals all on one CD...



Cheers
Iain

The engine revs only increase when operating the brakes. When I blocked the air intake to the servo & applied the brakes the engine revs didn't rise. I don't think it is the air valve as I don't have any increase in engine revs when not operating the brakes. Also when I took the plate off the air valve & operated the brakes the valves did move & then returned to the closed position after releasing the brakes. Of course as you will know this is not easy to see with the servo in position, my 77 year old body doesn't bend as easily or for as long as it used to.

How about you remove the pipe from the elbow where it pushes in at the back end of the servo, plug the pipe (not the rubber elbow) then start the engine and see if any air gets sucked in through the elbow? If it does then the diaphragm must have a puncture?

Hi saildrive
When you press the brake pedal it moves the control valve which opens the air valve to atmosphere if the other air valve does not close properly then you have air drawn from the servo body to the manifold.
Conversely when you block of the air to the servo you do not have a vacuum leak to the manifold causing rising engine revs.
These valves are critical to the operation and I know from experience that they must seal properly they can be a swine to seal due to corrosion on the seal face or poor condition of the air button face.

I agree John with your explanation, the problem is how do you check that the valve is seating properly with the servo in the car?
Your suggestion vxah would determine whether the diaphragm is the problem, I might be able to remove the pipe.

Saildrive
Did you carry out the first test I set
Run the engine two minutes switch off sit for two minutes then try the brake they should still be air in the servo

Hi John,
I did the test but I don't know what it proves because the servo doesn't work at all so if the vacuum was still ok I would feel no difference with the brakes. Am I missing something with this test?