The 'E' Type Forum

I have a problem with the brake booster ( servo brake ?): The brake pedal is quite hard to be pushed down, , i have tried at the beginning ( engine stopped) to pump on the pedal until it is very hard and then i start the engine and i have not any difference on the pedal. (The car is then hard to move by hand... ) I have checked the vacuum hose and i have a good succion with my finger at the end of the hose while the engine runs . i have not noticed a hissing noise anymore
I have dismantled the servo........and i don't find some thing wrong, any damaged rubber or something that i can see , may be a litle leak that i can't see ?
I have ordered new rubber seal , valve balancing diaphragm (2) and rubber buffer in case ? but i can't order the little rubber seal at the end of the air valve assembly(1) ( SNG can't sell it )
Any advice will be very appreciated

I have replaced the rubber seals and diaphragm and noticed no change on the brake pedal movement....
I'll see on the road the feeling with the foot pressure

Salut Yves,

I gave up on my Kelsey Hayes, probably unnecessarily with hindsight, and fitted this :









so can't help you.

But I do know that in the Knowledge Base there is an article that puports to explain step by step how it works and how to adjust it.

Part 1: https://www.dropbox.com/s/9hzpaajjoce0w ... 1.pdf?dl=1
Part 2: https://www.dropbox.com/s/xqevilada92wy ... 2.pdf?dl=1
Part 3: https://www.dropbox.com/s/v571pwvdeitzh ... 3.pdf?dl=1
Part 4: https://www.dropbox.com/s/j9n3vzpxdbo0v ... 4.pdf?dl=1

Some of the theory of how the master-cylinders work, and split the front-rear effort, it total, utter, and arrant nonsense, but since nobody has - to my knowledge - criticised the rest it might help you ?

Bonne chance !

The small seal comes in the kit from Here

Thank's abowie for the right link.... I'll test the servo on the road and will see .....

I have tested the car during 10 miles and all my wheels were jamed after 3 or 4 pressure on the pedal.....! they were free after +- 1/4 hour . Each wheel was blocked so the problem is obviously coming from the servo.



Did the measurements of "A" between 9.3 mm and 8.5 mm when the brake pedal is under pressure are correct ?
I can't measure the depression as the service manual says but i have a good succion at the end of the vacuum hose . I have tried different positions to the eccentric adjusting nut without succes , and the different parts under that eccentric nut seem not realy moveable.... i have no measure to refer to


I think it must be safe to send all the servo to a professional who will check and solve the problem....

and what was the conclusion?

It was solved with an "entretoise" , but i don't remember the thickness....!