Brake problem on R type special .

[Gavin Bartlett]

Help please ..... I had a squeaky noise coming from my front brakes on my R type special . When I got home I jacked the front of the car up and removed the wheels and drums . It was obvious that the shoes were starting to break up and small bits of the brake lining had come away which was causing the noise . I fitted new shoes , replaced the drums and wheels and tested the brake pedal . I had no pedal . I bled the system as per the manual by operating the master cylinder but the brake pedal was still non existent . I replaced the master cylinder as I noticed it was weeping . Bled the system again but still no pedal . This is where it gets interesting . With the front of the car jacked up and the brakes slackened right off by operating the brakes via the pedal there are no brakes . If I get underneath the car and operate the master cylinder they work .
I adjusted the slack adjusters and tried again . There’s something but I really have to push the pedal down . I adjusted them up a bit more to where the brakes were binding . When I tested it this time I could hear the servo unit making a noise like it was slipping and the brakes were no better .
Would anyone be able to shed some light on wether the problem could be the servo unit before I start mucking around with it ?
Any help much appreciated , Thank you .

[John Robins]

The servo bell cranks operate the master cylinder, not the foot pedal. There is therefore total dependence upon a working servo to get pressure in the lines to the front brake slave cylinders. The servo also augments the pedal effort to the back brake actuators. I think you have answered your own question if operating the master cylinder by hand applies the front brakes, whereas a rotating servo does not.

I forgot to say that I am assuming that your special has a standard braking system for an R-Type.

Prop the car up securely with all four wheels clear of the deck, get the back wheels turning slowly and see if the front brakes operate from the pedal. If they do, set up the system in accordance with the shop manual. If they don’t, or are feeble, you need to attend to the servo. The servo lining can become contaminated by oil which reduces its efficiency, to say the least.

If you want to send me a pm with your e-mail address I’ll send you an image of the gen in the handbook.

Cheers
John

Or try:-

https://rroc.org.au/technical/J_Brakes-5035.pdf

I’ve just checked that link on both google and my iPad and it’s a good’un. Takes a time to download on my antique system though. Some of the info in the narrative is out of date as it’s a MkVI manual, but if you look there are addenda.

[Christopher Carnley]

What John is saying is that the car has to be in motion, as the servo is gearbox operated, and only the servo turning will operate the front brakes.

Attach a length of stout cord (or baler twine) around the bottom of the master cylinder drop lever and pull from the front of the car to bleed and check the brake cylinder action.

[John Robins]

Not quite Christopher, I ‘m saying that the propshaft has to be going round to see if the servo is operating the master cylinder.

Cheers
John