Outer Limits 4x4 Board

I have replaced the front hub's of my FJ 40 with those of a disk brake Hilux.
I have put a new brake master cylinder,
I have bleed the brakes and adjusted the rear drum brakes accordingly.

When you press the brake pedal down the front ( Disc's ) lock up and the rear is not, if you realise the pedal and press down again front and back lock up no worries.

Why don't the back brakes ( Drum ) catch on the first time and you need to pump the pedal this just doesn't make sense.

Any help please.
Chris

check the brake shoe adjustments, had same prob with my landy

what was the brake master cylinder to suit

i have already re checked the rear brake shoes and they are set / adjusted properly so don't think that is the problem.

Regarding the Master cylinder it is the original FJ 40 type with the 2 brake fluid containers ( front and rear )

It seems that the piston inside the master cylinder max's out and the disk brakes lock on but the rear's won't then when you release and re press the back lock's on .
The pedal also stay's up higher when you press it the 2nd time.

Chris

I place my bet in air in the lines ..

But could think in how much fluid requires drums and how much requires calipers ..

When I swap my rear disc brake conversion in Tencha I have a sloppy pedal .. and nice brake after second push ..

After month of dealing with it, I make a change, buy a 80 series ( 4 disc brakes ) MC and run it ..

No more brake issues . and can lock all 37" tires at time ..

my master brake cylinder only has 1 resivour for fluid and I have factory front disk/rear drum.. maybe upgrade to a later brake master cylinder???

Do you have a brake booster at all? I have a canister under the passenger footwell which assists with braking.... just a thought.

You will have to get the correct master cylinder for the disc brake model. When i did the disc front conversion to my old 45 ute, it would do 'handbrakies' the rears would lock and the fronts just slow down.
Mine was a pita - no one could tell me what to do.
I ended up swapping the rear diff from twin slave cyl type to single (which is what they run on the disc from models), they still didn't work right.
Put the correct master cylinder for disc brake (single pot reservoir) all wheels braked ok but just not real good overall.
Put up with that for a while.
Then by chance, after my master cylinder blew a seal, i got hold of a complete master cylinder and BOOSTER of a disc brake model.

Brakes worked perfect straight away.

The booster off a disc brake model is twice the depth of the drum brake.

The moral to my story - i pretty much ended up running the complete braking system off a disc front model - only thing i didn't run was any vacuum tanks which some of them run.

If you press your brake pedal once, let it sit for a minute, press it again and the rears still don't work, then most likely you have twin rear slave cylinders, which will need alot of fluid to activate, and pumping the brakes twice quickly will pump them up a bit (the fluid needs a few moments to come back out of the slave cylinders, so quick pumping will build up fluid)

All i can suggest is change everything over.

Rob

Hay thanks for the reply's .
Have been running arround all day trying to sort this out NO ONE can tell you why it wont work properly.
Have found a complete diff with disk's on ( rear diff out of a shorty ) will this work with the original master cylinder or do i need to change it again.

Chris

your problem is not the diff but the brake MC and the fact its missing a booster..

swapping rear diffs wont fix nuthin...

I have a brake booster , and new Master cylinder.
We have narrowed the problem down to the fact that i have the old model brake set up with 2 cylinder's per side and the master cylinder doesnt have enough presure at the rear due to the disk brake conversion.

I just drove out to whoop whoop to see the disk brake diff and it is a full blown backyard job wich will not pass rego inspection even if you paid the bloke under the table. PISSED OFF.

Chris

As said you need to get the correct master cylinder to suit disc/drum, you currently have the drum/drum version. You need PBR no JB1526 available from most auto outlets eg: Repco.

But before you go any further, as Tapage said, (you havent answered this yet) are you 100% sure you have bled the system completely and in the correct sequence?

My tencha come with front Disc brakes ( :doh: ! ) but interesting to see the stock MC can't suply the amount of fluid needed by rear eldo calipers ..



Actually I use all my vacc to the brake booster ( swap the factory buster clutch with a non booster clutch cilinder ) and after the 80 series now the braking power could be best than my factory 80 series .. and that it's much to compare ..

Ray 185 : The brakes have been bled and adjusted over and over again old man is a Mechanic and is helping out while he is here on holidays but unfortunetly he doesnt do conversions like this back home.

Tapage : I can email you the pick don't know how to post on here if you want.

This arvo went and spoke with a brake specialist here in Darwin and he also said that the rear setup has to be replaced with the same setup as the disk/drum come out for the brakes to work so now i am trying to track down 2 end's of a single brake cylinder diff to replace with my double cylinder ones. Once i have replaced those i will change the master cylinder to the other one if required.

Any one have a single brake cylinder diff sitting @ home they want to sell bit's off?

Chris

Short 45 wrote:Tapage : I can email you the pick don't know how to post on here if you want.

ya sure .. tapage@4x4panama.com

Short 45 wrote:i have already re checked the rear brake shoes and they are set / adjusted properly so don't think that is the problem.

Regarding the Master cylinder it is the original FJ 40 type with the 2 brake fluid containers ( front and rear )

It seems that the piston inside the master cylinder max's out and the disk brakes lock on but the rear's won't then when you release and re press the back lock's on .
The pedal also stay's up higher when you press it the 2nd time.

Chris

you have the wrong master cylinder.

you need to get a dick/drum master out of a late model bj/fj

JEs

Short 45 wrote:Ray 185 : The brakes have been bled and adjusted over and over again old man is a Mechanic and is helping out while he is here on holidays but unfortunetly he doesnt do conversions like this back home.

Tapage : I can email you the pick don't know how to post on here if you want.

This arvo went and spoke with a brake specialist here in Darwin and he also said that the rear setup has to be replaced with the same setup as the disk/drum come out for the brakes to work so now i am trying to track down 2 end's of a single brake cylinder diff to replace with my double cylinder ones. Once i have replaced those i will change the master cylinder to the other one if required.

Any one have a single brake cylinder diff sitting @ home they want to sell bit's off?

Chris

you dont need to replace the rears, you just need to disconnect one of the slaves in the rear. Put the bleed nipple from the bottom slave into the top slave and put 2 nipples in the bottom slave to cap it off.

Jes

The first thing you should do, I have done this conversion as many otehrs have suggested is change your MC. The one you need (don't know which one RAY suggested) is the one to suit a 60s, they have disc front end, drum rear end and the same booster as a 40s

seriously, just start with the new MC, most problems will dissappear with it, if they don't then you will be closer to fixing the other problem you have, but you definately need to change you MC as suggested

Yeah the master I referred to is for a 40 series with factory fitted front discs and rear drums.

had any luck?

Hello people, been flat out working and havent had a chance to sort the brakes out yet .
I have driven it around the last few day's ( on and off trailer ) to get the windows installed and tray made and the brakes dont work to bad but not good enough.
(2 more job's knocked off the list before rego. i can see the light at the end of the tunnel )
Hopefuly this week i can sort them out if work permits.

Thank's Chris

your post is a bit unclear so I'll just say it anyway, you won't pass teh brake test with the brakes the way they are, pretty sure of that.

Well mine wouldn't down here in NSW anyway.

The booster Ray aand I suggested is a 10 min job on its own, then you have to bleed the brakes. Pretty sure that will fix it for you

Late but sure here the 40 MC pics ..



I never seen one like this before ..

Tapage wrote:My tencha come with front Disc brakes ( :doh: ! ) but interesting to see the stock MC can't suply the amount of fluid needed by rear eldo calipers ..



Actually I use all my vacc to the brake booster ( swap the factory buster clutch with a non booster clutch cilinder ) and after the 80 series now the braking power could be best than my factory 80 series .. and that it's much to compare ..

looks like a proportioning valve on there too

thats a pretty standard earlier one, pre 79?

they can be made to function with disc/drum

but i love the BJ42 MC as it has a load proportioning valve on the MC and the single reservoir, and bolts on.

bj on roids wrote:

Tapage wrote:My tencha come with front Disc brakes ( :doh: ! ) but interesting to see the stock MC can't suply the amount of fluid needed by rear eldo calipers ..



Actually I use all my vacc to the brake booster ( swap the factory buster clutch with a non booster clutch cilinder ) and after the 80 series now the braking power could be best than my factory 80 series .. and that it's much to compare ..

looks like a proportioning valve on there too

Nap .. it's the stock 80 series MC .... just need to eliminate ABS stuff ( or run ABS in my Tencha )

The MC on the orange 40 series above is the model used in Australia between 1975 - 79 on early model boosted brakes with 2 wheel cylinders per wheel set up in a leading shoe - trailing shoe configuration. Proportioning is done internally in the MC via a spring separation between the 2 pistons. This MC won't work with front disc calipers, it moves more fluid than the calipers can handle, that's why the front will lock up. The MC needs to be swapped out and replaced with a post 1979 MC from a disc/drum setup with the single fluid tank. Using a 60 series MC will work, but they had single rear wheel cylinders with less capacity than the two 40 series cylinders combined. It may not move enough fluid to the rear with enough pressure to be matched properly to the front. Best advice, get a late model 40 series MC from a truck that had disc brake front end. Next best, Get a 60 series MC and use that.

PS Hilux front calipers are basically the same as the 40 series front calipers so are perfect for this sort of conversion.

Hay thanks people.
My next job will be to replace the MC with one of the one's specified and see how that work's then chase a single cylinder style rear diff if the brakes do not improve.
The truck is not far off from getting rego but can't be done till brake issue is sorted.

Thanks Chris