No Brakes.

[Holden61,64]

The other day i was taking the Ek down the road, got to a t intersection and Brake pedal rock hard could barely get it to stop. less than about 10mm travel from the top.
Managed to stop the car and get it home safely. I thought the master cyclinder must have jammed or seized. I removed the Master cyclinder but the piston inside seams to move free enough. Could the brake booster be the cause of the pedal being rock hard. The brakes had been working perfectly the day before.

The car has hr disc brake front end with new rotors and pads. Re coed calipers.
The rear end is also hr with new pads and cyclinders and machined drums.

Master cyclinder is pbr but is old but had been working perfectly up till now.
Booster condition unknown but again had been working perfectly up till now.

There was no brake fluid loss at all and nothing stopping the pedal from moving.

Any Thoughts would be appreciated.
Thanks

[Trev]

Just recently replaced my braking system in my EK, all done and tried to bleed the brakes and I couldn't get a drop from the rear, so I disconnected the rear flexible hose and found it was completely blocked, it had swollen up inside.
My brakes were absolutely shit, this would have been the cause of my problem, hope this helps .

[fb delivery]

i'd be looking at the brake booster
couid be the diaphragm has gone

Rob

[Devilrod]

Easiest way to check if it's the booster is start the car up and if it runs rougher when you brake most likely the booster is knackered.

[Holden61,64]

Thanks guys i'll let you know how i go.

[rosco]

I'm leaning towards the booster - or lack of vaccuum in it.
If you start the engine then stop it, go back under the hood and pull out the vaccuum hose from the unit - you should hear a great rush of air enter the housing.
If this is not found to happen - I'd examine the check valve in the hose between the inlet manifold and booster - it may be jammed... don't meddle with it - replace it.

If you have the PBR unit, there are two valves inside which operate by action of a servo piston moving back/forwards as hydraulic fluid from the master cylinder dictates.
This action controls depletion/admission of vaccuum vs atmospheric pressure on the diapragm via the valves. The diaphragm then applices the necessary mechanical (instead of your foot) force on the servo hydraulic piston to apply the brakes (in essence - this is the equivalent piston in your master cylinder).

If there isn't any vaccuum present in the booster - you must physically apply greater force (equivalent of the diaphragm) on the master cyldinder... and, disc brakes demand considerably more force to attain the equivalent friction pressure on the rotors vs shoes and drums (make a comparison of the pad/rotor vs shoe drum areas).

You don't state which booster you have - there are two I know of, the PBR 40 and the Girlock one....I ditched my Girlock without using it - I could not obtain a "kit" to service it. I have a PBR 40-L which has worked perfectly for some thirty years - I do not know if a service kit is currently available for this unit.

I would further like to know if you have ever tried to stop the vehicle without vaccuum.... ie, rolled the vehicle down a slight grade with the engine stopped and having made a number of brake applications to destroy all vaccuum...? If you haven't ever tried this - DON'T do this anywhere but in a safe place - I expect this is exactly how you found your brakes..... I found that I almost had to bend the steering wheel to pull mine up.... one very good reason for a firewall mounted non-servo brake booster (we all wish - but the clutch master cylinder won't afford room for it).

We are all surmising at present....

Please keep us informed.

frats,
Rosco

[rosco]

Trev, forgot to respond to your post....
I suffered a loss of rear braking when I was a kid... blasted car wouldn't pull up properly and over-heated the front drums...
We found out that I had "kinked" that rear hose by connecting it from the wrong end (turning end) first..... did the same with the clutch.... aaarrgghhhh!, the learning process of doing it yourself.... but worse was to come about ten years later....

..... I am at a distinct disadvantage to just about every other FB/EK owner in existance...
When I modified my old bus - I built the entire brake system "new) and was "persuaded" to use synthetic brake fluid....... Penrite marketed it - silicone fluid... non-corrosive, non-absorbic, non hygro-scopic - absolutely no effect on paintwork.... it seemed too good to be true....

BUT

It costs both arms, legs and one of your "goolies"...
It cannot be mixed in any proportion with "normal" brake fluid - the rubbers in the entire system must be replaced (calipers included) or it will interact and turn them marsh-mellowy (for want of a better word).

Now, finding the exotic stuff is down to one outlet - thank goodness Harley Davidson use it in their bikes.... or I'd be up for a complete renewal of my system....
The small 390 ml bottle of synthetic costs me around $40 (or was back in about 2007).

I would never suggest anyone follow my path.... unless they fully comprehended the necessity to replace every rubber and understood that it cannot be mixed in any proportion......
The product is perfect for show vehicles - it does not "age" in situ - nor does it cause any deterioration of hydraulic brake componentry.
There are issues with heat performance even brake specialists cannot explain to me - but, unless driven madly in peformance applications - the medium is quite satisfactory for "service" use on everyday driven vehicles....

frats,
Rosco

[bat53retro]

put foot on brake start engine if peddle does not move it is the booster

[MeFB]

Easiest way to check if it's the booster is start the car up and if it runs rougher when you brake most likely the booster is knackered.

Yeah, that's what happens with Plastic the FB. I figured it must be the booster because it's sucking air through the damaged diaphram or dodgy valve and into the inlet manifold making the mixture way too lean. I'll have to get sorted out before rego (added it to the list).

[MeFB]

Here's a great guide from PBR that has a fault finding section. It talks about 'hard pedal' in there. Bad news for you and me is that the most likely cause is a knackered booster just like the other guys have said D'oh.

[MeFB]

Here's a great guide from PBR that has a fault finding section. It talks about 'hard pedal' in there. Bad news for you and me is that the most likely cause is a knackered booster just like the other guys have said D'oh.

Oops - forgot the link.

http://www.pbr.com.au/technical/documen ... sguide.pdf

[Holden61,64]

Yeah Removed the booster yesterday and found the diaphram was buggered, off for a rebuild for me.
Thanks for your help guys.

[rosco]

Thanks for posting the PDF link, MeFB - the forum will find it very informative.
It does give the basic principle of booster operation, but - does not mention the intricacies of the remote servo unit - such as most of us have fitted to our old buses...

I am currently looking for a description and repair instructions for the unit - not yet located....

frats,
Rosco

[Holden61,64]

Got my re coed booster in, bled the brakes and took it for a test run.
Brakes seem to work but need a fair bit of force on the pedal. More than they did before the booster crapped itself.
Started the car ,then shut it down, removed the vac hose and heard the air suck in. I'm assuming that mean booster is all good.
It just seams like you have to apply to much pressure on the pedal. Is there anything else that could be wrong.

[MeFB]

I would guess that there is still some air in the system - pedal would feel spongey if this was the case.

If your booster is in the normal position (driver's side front), then I think you're supposed to bleed from passenger side rear first, then driver's rear, passenger front and then driver's front. If you get out of whack with the pedal pushing and tightening / releasing, then you can suck air back into the system.

Other than that, did you use fresh brake fluid?

Well, that's my knowledge exhausted The other guys would be able to add more.