Cant bleed brakes on hilux

[Rota]

Hi guys i was hoping someone here might be able to give me some ideas.

Recently i have bought a hub spacer kit for my 85 hilux along with new vented rotors and some second hand ifs calipers. So the calipers are a bit bigger than my old ones but i wouldnt think that would be the problem.

Anyway so i have put on the spacers and new rotors with calipers then bled the whole system from the rear left to the front right. pump up the brakes and they seem to work fine. Then turn the car on and with the added vacume the pedal goes straight to the floor and is very spongy.

Bleed the system again and it still doesnt work. I then clamped off the front brake lines to the calipers and the brakes work and are very hard, so i assume that the calipers were stuffed.
So then i got my hands on another set of calipers, bleed up the whole system and still the pedal is soft and can go all the way to the floor when the cars turned on.
I have even tried reverse bleeding the calipers with a syringe. Also i have taken the calipers off, tapped them with a plastic hammer to try and free any bubbles then put more brake fluid in with a syringe.

I am at a total loss for ideas. All i can assume is that maybe both calipers are stuffed but i would have thought that that would be pretty unlikely.

Does anyone have any ideas????

[Roctoy]

have you bled the proportioning valve under the tray as well?

[Rota]

have you bled the proportioning valve under the tray as well?

No i havent, but i havent had to before when bleeding the brakes on my hilux.

Also when i have the front brakes clamped off at the flexy lines the rest of the system builds pressure fine.

So im assuming everything is fine up to the calipers or the master cylinder isnt coping with the new calipers at all????
But they are only a bit larger than the old calipers and they worked great with them.

[tehekho]

have you bled the proportioning valve under the tray as well?

No i havent, but i havent had to before when bleeding the brakes on my hilux.

Also when i have the front brakes clamped off at the flexy lines the rest of the system builds pressure fine.

So im assuming everything is fine up to the calipers or the master cylinder isnt coping with the new calipers at all????
But they are only a bit larger than the old calipers and they worked great with them.

only a bit larger?
Whats the total piston area?

[Roctoy]

i've run the bigger hilux calipers (suit vented discs) before off the standard 84 model master cylinder.

i did have problems with the thin metal shims that were on either side of the pads. They were slightly bent (enough to push the piston back into the caliper a bit) this caused the first push on the pedal to go to the floor, then the next pump they were fine. I threw the shims out and never had a problem again.

just food for thought.

[Rota]

I havent measured all the pistons to determin the increase. But visually the SFA calipers have 2 large pistons and 2 medium and the IFS calipers have 4 large pistons. The 4 large ones of the IFS calipers are the same size as the 2 large ones in the SFA calipers.

But my understanding was that a larger master cylinder was to give better brake feel?

At the moment i cant get any reasonable pressure. I can only get them to grab hard if i do about 5 quick pumps and then it will only hold for a couple of seconds.

Also i cant see any fluid leaking anywhere.


I will try and look for any flexing or anything tonight i guess?

[gavanchua]

i've got a feeling that your brake booster might be leaking or isn't big enough to support the bigger brakes. I had brakes like that once on my previous ride when i upgraded from front only disc to full disc on the car using the old brake master pump and booster and the brakes felt just like what you've described... it brakes but it doesn't build enough pressure to grip hard and it's spongy. Swapped it over to a 4 disc brake model master pump and booster and it works great! (noticable difference between the original and the 4 disc brakes booster is that the 4 disc model brake booster is thicker and has a bigger master cylinder)

[Evski]

Also check your wheel bearings havent worked loose. I had the same problem, and as the bearing were loose this caused the wheel to wobble slightly, and spread the pads appart. Took about 2 or three pumps to get it back to normal. Pretty bloody scary, so went all out and got the whole system rebuilt including DBA slotted rotors. Money well spent.

Another issue could be that your master cylinder has packed it in after being bled. If you were a little too aggressive on the pedal, this can cause the seals in the master cylinder to wear resulting a complete lack of feel.

[Rota]

I dont think the mastercylinder doesnt have enough power for the new brakes. The size difference is not much and i have seen mates upgrade calipers before on their cars without doing the master cylinder.
Im only putting slightly larger calipers on, not swapping out drums for disc brakes.

Also it still wont build pressure when it is only operating the rears and only one of the front calipers (with the other clamped off). So that would be less work than doing 2 of the older front calipers.

I did think that the master cylinder may have died from being bled and the seals passing over old rusted areas that havent been used before (at the bottom of the pedal travel).
But with the front calipers clamped off it bleeds up fine.

Not really sure what to do, the hilux is parked pointing up a hill on our driveway at the moment and i have read that that can make problems for bleeding the master cylinder. so i might try moving it. But thats about all ive got so far?

Other than that i might try and split the calipers and have a look inside them, if thats not too hard?

[lukethedork]

Are the bleed nipples on the TOP of the calipers? If you put the calipers on the wrong side the bleed nipple will be on the bottom of the caliper.

Luke.

[Rota]

Yeah bleed nipples are at the top

[mutilated]

Replace the master cylinder and you will be fine. It sounds like the increased fluid capacitiy in the callipers is too much for the master cyl to give a full application. If not the secondary piston may be stuck in the master cyl. Give it a tap on the end with a hammer to free it up. What method are you using for bleeding?

[Rota]

Replace the master cylinder and you will be fine. It sounds like the increased fluid capacitiy in the callipers is too much for the master cyl to give a full application. If not the secondary piston may be stuck in the master cyl. Give it a tap on the end with a hammer to free it up. What method are you using for bleeding?

I will try tapping the master cylinder.

I have been using a 1 man brake bleeder kit. But i have also tried the old method of using 2 people. 1 to pump up the brakes then the other to crack the bleed nipple.
I have even tried reverse bleeding with a syringe..

[DUDELUX]

If you need to, you can adjust the pushrod between the booster and the master cyl.
Theres also the pushrod at the top of the brake pedal that you can adjust.
I adjusted both in my recent brake issues, and it has seemed to fixed it.

And my 5cents, is, those 1 man brake bleeding kits are a joke.
I used an old glass coffee jar, half full of clean, new brake fluid, and a piece of clear hose to fit on the bleed nipples.
Bled the brakes one by one, with me going from the brake pedal, pumping it down halfway and back, over to the brake to close the nipple once the air bubbles had stopped.
I know that you bleed the longest line first, and the shortest line last, and then the LSPV after that.

I know theres a thread here that has some really good info on front brakes. Posted by me, about some of the fun times I had when learning how to do brakes.

Good luck mate.

[mutilated]

be very careful if you adjust the pushrod in the booster as if done incorrectly it can cause a violent brake application. As said above use a clear hose and a bottle with some clean fluid in it and get someone to watch the hose for bubbles while you pump away. Never pump the pedal all the way to the floor as this is when the piston can stick in the master cylinder. Good luck.

[DUDELUX]

When adjusting the pushrod in the booster, theres a grease trick that someone told me.
Its something like this....
Pull the master cyl away from the booster, just enough to get your finger in there,
Put a small dab of grease on the end of the pushrod with your finger,
Refit the master cyl and tighten up,
Take the master cyl off again,
If the grease has been smeared, then the pushrod is too close and is activating brakes too soon(or something like that),
Adjust the pushrod until the grease doesnt get smeared,
And keep fitting/removing the master cyl and doing the grease test until its right.

Then theres the pushrod at the top of the brake pedal, you can adjust that too.

[mutilated]

This should only need adjusted if there is too much free board in the brake pedal and normally wont need to be adjusted from the factory settings unless aftermarket parts are used that may have slightly different tolerances. If its not done right and there is slight pressure on the Reaction Disk then the brakes will go on fully with the slightest touch of the pedal. I would not recomend adjusting the pushrod in the booster for that reason alone and the fact that it should never require adjustment after being set at the factory as it is not a part that wears.

[DUDELUX]

Well I have fitted later model Lux front rotors and bigger calipers, and an early 80series booster and master cyl.
Brakes were working great, rears were pretty much non existant, and then when I got the rears done/rebuilt, the pedal was solid, and rear brakes were grabbing badly, so I was speaking to someone and he mentioned the grease trick, and the pedal pushrod, and Ive done both and it seems to be good now.

[Rota]

Ok well i tried tapping the mastercylinder and that hasnt done anything i dont think. Also it was parked on an incline before so i have got it on flat ground now but nothing has changed.

The one man brake bleeder i have is pretty good i think, it has about half a meter of clear hose going into the bottom of a bottle and i have had it sitting high above the caliper to let any bubbles rise.

I think my next attempt will be to try and get another mastercylinder and booster off a hilux with the same calipers.

my brakes work a bit atm, if i pump them about 5 times they seem to grip hard. Does that indicate that the mastercylinder might be stuffed?
I cant see any brake fluid leaking out anywhere though. Im assuming it might be a seal inside the master that is stuffed?
Its just funny that with the front calipers clamped off it works fine. I would have thought if a seal was gone in the master the brakes would never work properly?

[mutilated]

If its a seal in the master cyl then the pedal will drop slowly with pressure on it. it could be air or it could be not enough fluid output from the master cyl. are there any bubbles coming out when you re-bleed the brakes or not? if no air I would say the output is too small for the larger calipers. After a few pumps the pedal will come good as all the fluid is pushed into the pistons but once the pedal is released and the pistons move back to their resting position the pedal will be crap again.

[old ed]

Before you spend anymore money check your rotors and calipers. If anything is loose/warped/twisted etc and is causing the pads to move back from the rotors you will have to pump the pedal to get the pads into contact with the rotors before you can develop any pressure. The pads should remain in contact with the rotors at all times. It has already been suggested to check the wheel bearings and anti-squeal shims. Even if the pads only move .5mm it will probably take at least a m/c full of fluid to move them back into contact with the rotors. The fact that if you clamp off the front the rear works ok is a pretty good sign that you have excess pad travel. It's possible that the seals in the used calipers have stuck to the bores and are pulling the pistons back,how long were they laying around getting rusty?

[lukethedork]

I think my next attempt will be to try and get another mastercylinder and booster off a hilux with the same calipers.

my brakes work a bit atm, if i pump them about 5 times they seem to grip hard. I cant see any brake fluid leaking out anywhere though.
Its just funny that with the front calipers clamped off it works fine.

Don't go wasting your money on new parts until you have all the air out of the system.
The fact that it works with the front brakes blocked off should lead you to believe that the master cylinder, vacuum assist and rear brake systems are all in working condition.

This then leaves a possible problem with the front brake lines, front calipers, front discs, the master cylinder being too small, or the fluid reservoir being too low causing drainback.

The front brakes are almost always the ones that cause trouble for bleeding on cars.
Get someone who knows how to bleed brakes to bleed them. Then waste money on new parts.

Luke.

It's possible that the seals in the used calipers have stuck to the bores and are pulling the pistons back,how long were they laying around getting rusty?

This is probably the best piece of advice I have seen in this thread. Check the seals.

[Ice]

seal kits seem to be pretty cheap $35 ish for 80 series callipers

the pistons themselves mount up in $$$ pretty quickly though

[Rota]

I think my next attempt will be to try and get another mastercylinder and booster off a hilux with the same calipers.

my brakes work a bit atm, if i pump them about 5 times they seem to grip hard. I cant see any brake fluid leaking out anywhere though.
Its just funny that with the front calipers clamped off it works fine.

Don't go wasting your money on new parts until you have all the air out of the system.
The fact that it works with the front brakes blocked off should lead you to believe that the master cylinder, vacuum assist and rear brake systems are all in working condition.

This then leaves a possible problem with the front brake lines, front calipers, front discs, the master cylinder being too small, or the fluid reservoir being too low causing drainback.

The front brakes are almost always the ones that cause trouble for bleeding on cars.
Get someone who knows how to bleed brakes to bleed them. Then waste money on new parts.

Luke.

It's possible that the seals in the used calipers have stuck to the bores and are pulling the pistons back,how long were they laying around getting rusty?

This is probably the best piece of advice I have seen in this thread. Check the seals.

Ok well ive bled the brakes many times before without a problem and a mate whos a qualified mechanic gave me a hand with it at one point too so i dont think its my method of brake bleeding.

Brake lines should be fine as they worked sweet before hand.

front discs are brand new

Dont think its the seals on the calipers stuck as i have allready moved the pistons in to fit the new brake pads. Apparently they were only off of the car for 2 months, but that may be a lie.

Not really sure what you mean by the fluid reservoir being too low and causing "drainback"? i allways have it filled up to prevent air getting in the system again if thats what your talking about?


Ive about had enough of this job now anyway hahaha. Ive probably cycled about 5L of brake fluid through this thing. Im probably just going to handball it onto a brake specialist when i get a chance.