Next to no brakes

[phil]

1961 series 2A. in the process of a rebuild. Almost ready for rego.
Brakes quite good on a static test but when test driven the brake pedal dissapears towards the floor at an alarming rate, but a few pumps and it is restored until next time. No visable leaks, shoe adjustment is fine and I have bled and bled the system. anyone with any ideas.

[101RRS]

I would have said shoes adjustment - but you said you have done it

[Phoenix]

What condition is your master cylinder in?

[JDNSW]

Try clamping off the hoses. If the brakes are solid with all clamped off it will test your m/c. Same with front clamped off for the rear and so on. My guess is either there is still air in the system, or the brake adjustment is not working properly. One possibility is the adjusters are moving when the brakes are used due to being too loose or worn, another is that the return springs are incorrectly assembled so the shoes are not centralised, so the adjuster doesn't work properly. You don't say whether it is an 88 or 109.

[Frenchie]

Those brakes are very very hard to bleed properly, they really need to be pressure bled. Take it to a brake place and get them to do it.

I put up with shocking brakes for years in my IIA. They were still bad after a full rebuild even after bleeding, so I took them to a professional and for $15 I had proper brakes. 8)

[DEFENDERZOOK]

<span style="color:blue">are your drums round?
if the drums are out of rounds they will push the shoes back further and will need to be pumped before they work.....



otherwise sounds like master cylinder to me....</span>

[phil]

Thanks Guys for the replys. In answer to your questions, master cylinder and wheelcylinders are only about 1 year old. Shoe adjustment is good but day off today so I'll reset them again. As far as I know drums are round, I will also clamp off and test brakes, and if all that doesn't work its off to get them pressure bled, I'll keep you all posted.

[DEFENDERZOOK]

<span style="color:green">age of components does not mean much.....brand new components fail or have faults....

if the vehicle has been sitting it could also cause premature failure of seals in master cylinder....

a simple seal is all that may be causing the problem.... but which one.....

how do you bleed the brakes.....as in which method do you use?</span>

[Hellspawn]

From what's been said so far sound a lot like the non return valve in the master cylinder isn't sealing properly. In short the valve is supposed to be forced shut as the pedal pushes the plunger along directing fluid to the outlet to the brakes. When the pedal returns the plunger it's supposed to suck any additional fluid into the cyl used in the last stroke. If that valve doesn't seal the fluid goes back to the resvr instead of the brakes unless the pedal is pumped building up the pressure enough to temporarily shut the valve.

Not alot of cost for a new master cyl. so easy enough to buy new with warranty than fix the old.

Never heard of pressure bleeding. I just use out of date oxygen tubing as the end fits on the bleed nipple and long enough to sit in a plastic bottle on top of the tyre so becomes a one person operation. Yep they work, enough for a 70%av. on the last RWC, which aint bad from all round drums. :wink:

[UncleHo]

G'day Phil style_emoticons/<#EMO_DIR#>/smile.gif
I will take a punt that this is a 109 GS :?: Fitted with the CB Master Cylinder (steel with the large nut at the rearend 1" bore) and you followed the instructions in one of the workshop manuals that stated ; back off the adjustment before bleeding the brakes, :wink: Try this :wink: Adjust up all wheels until locked THEN Bleed the brakes :wink: sequence is LEFT Front, RIGHT Front, LEFT Rear, and RIGHT Rear, If you suspect air in the M/cylinder bleed it FIRST by slightly opening the outlet pipe (rear pipe on M/cyl closest firewall) while somebody is SLOWLY pressing the brake pedal, close off before pedal hits the floor, this gets the air that is trapped in the spring recess in the nut style_emoticons/<#EMO_DIR#>/smile.gif
hope this is of some help style_emoticons/<#EMO_DIR#>/smile.gif

NOTE: If it is a 109 make sure that you have a 1 inch bore Master Cylinder as the SWB uses a 3/4 inch bore and does not move suffient fluid to give brake shoe pressure. 8O I am aware of at least 1 fatality as a result of incorrect M/cyl diameter :wink:
cheers
Rocket style_emoticons/<#EMO_DIR#>/smile.gif

[Hellspawn]

Originally posted by rocket

NOTE: If it is a 109 make sure that you have a 1 inch bore Master Cylinder as the SWB uses a 3/4 inch bore and does not move suffient fluid to give brake shoe pressure. 8O I am aware of at least 1 fatality as a result of incorrect M/cyl diameter

Glad you remembered that rocket. style_emoticons/<#EMO_DIR#>/biggrin.gif Thinking about it that would cause similar symptoms to those described if the wrong cylinder was used.

[DEFENDERZOOK]

Originally posted by rocket
G'day Phil style_emoticons/<#EMO_DIR#>/smile.gif
I will take a punt that this is a 109 GS :?: Fitted with the CB Master Cylinder (steel with the large nut at the rearend 1" bore) and you followed the instructions in one of the workshop manuals that stated ; back off the adjustment before bleeding the brakes, :wink: Try this :wink: Adjust up all wheels until locked THEN Bleed the brakes :wink: sequence is LEFT Front, RIGHT Front, LEFT Rear, and RIGHT Rear, If you suspect air in the M/cylinder bleed it FIRST by slightly opening the outlet pipe (rear pipe on M/cyl closest firewall) while somebody is SLOWLY pressing the brake pedal, close off before pedal hits the floor, this gets the air that is trapped in the spring recess in the nut style_emoticons/<#EMO_DIR#>/smile.gif
hope this is of some help style_emoticons/<#EMO_DIR#>/smile.gif

NOTE: If it is a 109 make sure that you have a 1 inch bore Master Cylinder as the SWB uses a 3/4 inch bore and does not move suffient fluid to give brake shoe pressure. 8O I am aware of at least 1 fatality as a result of incorrect M/cyl diameter :wink:
cheers
Rocket style_emoticons/<#EMO_DIR#>/smile.gif



hey rocket...this all makes good sense...but....
shouldnt the brakes furthest from the master cylinder be bled first?
in order from furthest to closest?
what im asking is... arent the back brakes further from the master cylinder than the front ones are?

[incisor]

in theory the longest pipe should be bled first, then the next longest etc etc.

[DEFENDERZOOK]

<span style="color:green">thats my point...but i am unfamiliar with early landys....

i would have thought the furthest would be one of the rear brakes....</span>

[incisor]

it is style_emoticons/<#EMO_DIR#>/tongue.gif

it was probably late and the old fella was tired and couldnt put to paper what his mind was saying to him ....or he was full o' scotch or he was wrong style_emoticons/<#EMO_DIR#>/tongue.gif