Girling 2B servo problem

[saildrive2001]

My servo in my Elan S4 just stopped working & when I push on the brake pedal the engine revs rise when at idle. I assume that there is a leak in the system but the hose from the cyl head to the servo is good. Without removing the servo does anyone have any ways to test what part of the servo may be the trouble?

[oldelanman]

Hi Keith,
Do you have a Workshop Manual ?
There is a page in the Braking System section on testing the servo which may help you determine where the problem is.

[Hawksfield]

Oldelanman
Remove the air connection plate on the side of the servo make sure that the rocking air valves are ok and not full of fluid. That's about all you can do without removing the unit. Also a quick test is let the engine idle for a couple of minutes and switch of ignition. After a delay of a minute there should still be vaccum in the system to operate the brakes.
Good luck

[saildrive2001]

Hi Roger, I do have a copy of the manual & to be honest forgot to look at it.
Thanks for the suggestion Oldelanman, I will check it out.
One other thing I didn't mention is that when I am stopped, if I ease my pressure on the brakes so that they are still only lightly applies then the idle returns back to normal. I have also over the years since the rebuild in 2013 had the fairly common problem of the brakes staying on & a very firm pedal. To release them I had to do what others have found works & that is to jab the pedal hard & they release.

[englishmaninwales]

Not the answer you’re looking for…apologies. When mine failed, I removed it from the system and fitted Mintex 1144 front pads, IMO gives a much better feel and progression to the brakes. But, horses and courses!
Malcolm

[saildrive2001]

I removed the air connection plate & got a small amount of brake fluid out but not a great deal. I'm not sure that I can tell anymore from looking at the area, especially with the physical gymnastics need to see them.

[vxah]

Sounds like you might have a punctured diaphragm? When the brakes are not applied vacuum is supplied to both sides of the diaphragm, when you apply servo assistance vacuum is closed off to the rear of the diaphragm by the rocker valve and air pressure allowed in creating pressure on the push rod. A puncture in the diaphragm allows that air to get through and into the engine.

[saildrive2001]

I agree that a leak in the diaphragm could be the cause, I'm also trying to figure out it anything else could cause it. Unfortunately I think it will be a servo out project to determine the problem & repair it.

[sprintsoft]

Hi Keith,

Leaking brake fluid…
Leaking air back into the inlet manifold…
Not releasing the brakes…

These old servos don’t go on for ever, I’d say you have enough reasons to get it professionally overhauled and re-sleeved, it’s not expensive, and you can enjoy driving it again!

Iain

[saildrive2001]

I had it rebuilt professionally in 2013 the year I got my car back on the road. I've only done about 12,500 since my rebuild.

[sprintsoft]

I understood they returned it to you with the sticking problem?

[saildrive2001]

They never could solve the sticking problem even after three times, each time they said it worked perfectly on their test bench. Another Elan owner here also had the same problem when he had his servo rebuilt. The company specializes in rebuilding brake systems so are well known in the area. The sticking on problem slowly got better over the years but never did completely disappear.

[sprintsoft]

Keith,

I have heard of it, but not experienced it (on three cars with this servo type).

Brian here below, on his last post, seemed to have found the cause and fixed it, it might provide a clue when you overhaul it...
https://lotuselan.net/forums/viewtopic.php?f=42&t=1587&start=15

Iain

[saildrive2001]

Iain,
Thanks for the link. I haven't had time to do any testing & it's going to be raining here all weekend but I hope to do some testing next week. I will post if I find anything. A friend suggested blocking off the air intake to check that there isn't any air entering the servo from another source?

[sprintsoft]

https://volvo1800pictures.com/document/Girling%20Hydralic%20Servo%20unit%20MK%202A%20and%202B/Girling%20Hydralic%20Servo%20unit%20MK%202A%20and%202B.pdf

Keith, take a look at this, I suspect the sleeve, it’s spring and the ball bearing are not re-opening, they are getting stuck…

Why? The bores are not clean, some corrosion has crept in maybe?

Iain