Spongy brakes

[Z()LTAN]

Hey fellas,

Trying to bleed up my new brake system, using standard 15/16 bore toy master linked to large chev 1 ton brakes. Got all the air out but can't get decent pedal feel. If I pump it up and pushes right to the floor it pulls the car up but just.

Done a bit of searching and found people getting the 3/4 masters to work. Maby my brake pistons are a whole lot larger?

Should I do a 80s 1" master swap?

[Z()LTAN]

Update, can get it to go hard with engine off. Engine on then goes to the floor.

Air?

[84sloth]

having the exact same issue with my cruiser tom!

[turbo gu]

Can you change the feel of the pedal by clamping off front or rear brakes?

I know its a silly question but you don't have any calipers on with the nipples pointing down?

[Struth]

Are you using a vacuum bleeder, my system will not bleed any other way, just cannot get the air out without vacuum.

Cheers

[Z()LTAN]

All caliper bleeds are upper most. I'll try isolating.

I'm bleeding it manually by myself, hooked up a sosvac on it today. Made it a little better but still average.

[RAY185]

Got much pedal freeplay? What's pushrod to master cylinder piston clearance like?

[Z()LTAN]

exactly as it was before ray, none of that has changed.

[RAY185]

Ahh sorry. Thought you changed master cylinders too. Then it definately sounds like the master isn't suited to your new caliper setup, as you suspect. Not being familiar with chev brakes, what is your new setup compared to your old one?

[Z()LTAN]

It's just a great deal larger. Just not sure if the 15/16 displacement is enough to charge all brake calipers.

I will buy a proper vac bleeder and isolate tomorrow.

[Fakey]

I had the same prob with my Bj74 when I went with discs all round. I always needed someone to help bleed it. Vacuum or reverse pressure bleeders didnt work for my truck itd always trap air an was a real PITA.
Trying to isolate front to rear is a good start. let us know how that goes

[MogLux]

It's just a great deal larger. Just not sure if the 15/16 displacement is enough to charge all brake calipers.

I will buy a proper vac bleeder and isolate tomorrow.

You have hit the nail on the head there mate... If you look at the trucks in the states that run these axles stock the master cylinders as minium 1" bore .. When i was running hilux axles with 4 wheel disk brake the standard 15/16 master cylinder wasnt large enough for those .. your brakes are bigger than lux ones.. I now run a VT commodore booster and master cylinder 1 1/4" bore..

Let me guess if you double pump the pedal the pedal is firm and doesnt fade like it would if you have air in the system.. right.. if so its to small to fill all the cambers and you will need a larger master cylinder.

You could possibly try a 80 series master cylinder there 1" bore but i would recommend going larger than that too.

Matt

[Fakey]

If the pedal goes hard by pumping it then typically this is either caused by air in the system being compressed or excess caliper piston travel. Ive run Surf four pots all round with a surf master and an adjustable rear proportioning valve an the pedal an brake force was great

Excess piston travel can be caused by tight seals in new calipers pulling the pistons back too far(doing their job too well) or if your wheel bearings are too loose allowing the hub/disc to move when the brakes are applied, when the hub moves back to its relaxed position it pushes the pistions back too far for the master cylinder to take up in a single brake application

If you pump the pedal till it goes hard an hold it does it stay in the same position or drop to the floor?
Would be interesting to know what your calipers are out of an what size master cyl they are typically rub with

[evanstaniland]

I'm not stalking Tom just see if any opinions here

So people excuse the price as I'm not asking about your budgets more if this would be a valid option?

http://www.autoworksparts.com/electric_ ... ooster.htm" onclick="window.open(this.href);return false;

:

[turbo gu]

I wonder what the feel of the brakes would be like with that. It would make mounting brakes a heap easier in tight areas

[MogLux]

I'm not stalking Tom just see if any opinions here

So people excuse the price as I'm not asking about your budgets more if this would be a valid option?

http://www.autoworksparts.com/electric_ ... ooster.htm" onclick="window.open(this.href);return false;

:

Evan you could probly be able to source this stuff through work alot cheaper as well.. its just an accumulor setup.. would work awesome i reckon...

[mmaaxx]

Im in the exact same position. Tried fitting bigger calipers along with my dual diaphram booster and couldnt get any pedal pressure even after bleeding it properly.

the factory 13/16" master cylinder is too small to pump the extra fluid pressure required.

I bought a prado 90 1" bore master cylinder which fits. Gonna fit it up next week when on holidays.

In respect to your situation a suggestion:

Either use a T100 Dual diaphram brake booster and 1 1/16" master cylinder which will give great braking performance.

The mounting pattern of the T100 is exactly the same as the 80 series cruisers to the fire wall and all pre 05 hilux's aswell, both IFS and solid axle.

The other option if you need even greater braking power is to get an adaptor for the T100 booster and mount a Chev Truck 1.5" bore master cylinder.

If you need proof of the compatability of those units above, check the gasket part number between the 80 series, hilux and T100...all use the same gasket to the booser to the firewall.

[ae86levin]

When I did my Hilux 80 series master / booster conversion I found making a pressurized bleeder worked very well.
http://www.outerlimits4x4.com/viewtopic ... 2&t=228173

[guzzla]

I spent ages trying to get a good brake pedal after changing some brake lines. After bleeding them a million times and testing everything else, I decided to re-bleed them a different way - here's what I did and will most likely fix your issue...

Take a 5m length of 5mm PVC clear tube (make sure it is clean)
Clamp one end over the bleed nipple furthest from the MC and secure the other end into the brake fluid in the baster cylinder.
Ensure the MC is full of brake fluid.
Now pump that brake pedal about 50 times and watch all the air you though wasn't in there, bleed itself off into the baster cylinder.
Sometimes it can be another 10 pumps of the pedal before you'll see more air bubbles so keep pumping until you're sure there;s none left in that caliper/brake line.
When no more air can be seen in the line, close the nipple.
Repeat as above, working your way to the MC in the normal sequence you'd bleed the brakes.

NOTE: before doing the above procedure, ensure the brake system has been flushed properly with clean fluid.

The best part about the above way is it allows you to constantly bleed each caliper without having to stop and top up the MC.
I got a heap of big bubbles out of my system doing it this way and when done, the pedal was the best it had ever been.

Good luck.

[Z()LTAN]

Changed to the 80s 1" master. Made it better but still goes to the floor.

Should i be looking at residual pressure valves perhaps?

[mmaaxx]

I got my brakes sorted recently.

Dual diaphram booster, standard 13/16 master cylinder.

Got a shop to do it as I wanted a professional brake bleed.

I fitted larger calipers with bigger pistons by the way.

The shop found out that when ARB did my diff gears, they didn't adjust one of the rear drums/shoes properly, it wasn't adjusted. At all.

Done some LPSVmods too.

Brakes now work better than my wifes kluger on 35's..

Not sure if it will help but may give you some idea.

[joshy]

You sure one of the calipers isn't sticking or something? I had the same problem with my brakes until I went to rear steer and changed calipers, which were larger, but all of a sudden I had brake pedal feel back.

[Guy]

I got my brakes sorted recently.

Dual diaphram booster, standard 13/16 master cylinder.

Got a shop to do it as I wanted a professional brake bleed.

I fitted larger calipers with bigger pistons by the way.

The shop found out that when ARB did my diff gears, they didn't adjust one of the rear drums/shoes properly, it wasn't adjusted. At all.

Done some LPSVmods too.

Brakes now work better than my wifes kluger on 35's..

Not sure if it will help but may give you some idea.

why would you put 35's on a Kluger ?

[Z()LTAN]

I measured everything up, full displacement on a 1" bore 80s master cylinder will only move my wheel cylinders 2.2mm. Which is pretty much the seal return distance.

Swing and a miss... Time to find a 1 1/4 - 1 1/2 master

[turbo gu]

I measured everything up, full displacement on a 1" bore 80s master cylinder will only move my wheel cylinders 2.2mm. Which is pretty much the seal return distance.

Swing and a miss... Time to find a 1 1/4 - 1 1/2 master

the other option would be a stepped master. From memory vt onwards commodores have one with the first stage pushes the pads out quickly then the 2nd stage applies the pressure.

[evanstaniland]

Did you look at the electric setup I linked! I still have to sort out my brakes on my danas so watching closely!!

[Z()LTAN]

I did Evan, but really it's alot of money and alot of messing around.

I'm going shopping today, hopefully find something.

[MogLux]

Ill have my brakes bled the week i return from my travelling... so 2nd weekend in march hopefully.. I have f350 calipers front and rear running a vt commodore master cylinder and booster.. there shouldnt be an issue with pedal..

That electric set up looks good but $$$$$$$$$$$$$$$$$ crazy priced.

[Z()LTAN]

I fitted a 1 1/8 master from a Toyota coaster, brake is still a little spongy but locks up all wheels.

It still drives through in low low at idle tho...

I'll try to find another with slightly more displacement but I'm happy with it for TT.

[evanstaniland]

Ill have my brakes bled the week i return from my travelling... so 2nd weekend in march hopefully.. I have f350 calipers front and rear running a vt commodore master cylinder and booster.. there shouldnt be an issue with pedal..

That electric set up looks good but $$$$$$$$$$$$$$$$$ crazy priced.

let us know how yours goes Matt.

its not that crazy priced when you look at its purpose! id be happy to spend the $$ knowing my breaks will perform 100%