ma61 spongy brakes after upgrade and many bleedings

[naten]

Howdy,

Just finished my brake upgrade on the MA61 (Z32 4 spots and rotors on the front) and im having trouble getting a good pedal.

When i first bled it the MC crapped out so i got a new one.

After bleeding the new one i have a pedal which travels to 1/2-2/3 before stopping power starts. Ive bleed it three times now and now air has been seen since the first bleed.

Anyone got any other suggestions?

Cheers
Nathan

[naten]

hmmmm just had another play

can feel the brake booster rod hitting the MC maybe with maybe 2-5 mm pedal depression so that seems ok to me

Once i turn the car off and press the pedal down 2-3 times it becomes hard, will hold this hardness till i start it again, then it gets soft and spongy

brake booster fooked?

[EldarO]

sounds like its working as it should, you'd expect it to get hard with no vac.

my hilux is doing the same fucken thing and its shitting me up the wall sideways.

[naten]

same been weeks trying to sort this dam brake upgrade out now.

Hmmmm thats true if the brake booster was fooked the brake pedal would be harder as its not providing any assistance?

Just wierd that it will get nice and hard with it off (does this mean no air in the system?) then soft when started. tried scouring the net for a reason for this but no luck

[PlacentaJuan]

i had something like this when i changed brake boosters (to fit new engine)

as well as the booster having a cracked stud and letting air in, i had pressed the pedal too hard the first few times and broken a valve in the booster (not sure what the valve is)

after i got it fixed i was advised to only press the pedal 1/2 to 3/4 of the way when bleeding and to also PRESSURE BLEED where you build up fluid pressure before releasing fluid from the caliper, and make sure you shut off the fluid before the pedal bottoms out, and you still have plenty of pressure in the system.

it takes a little bit longer but i allways do it this way.


also after using ebc pads have allways had what i consider to be a slightly spongy pedal and got used to it, but this stopped instantly once i put in the ferodo pads.

[wa5]

not trying to state the obvious.... But a Mate once bought a Valiant with reconditioned calipers.... and he could not get a decent pedal...... took it to a brake place, and they had it fixed in around half an hour...

The calipers had been fitted to the wrong sides and were upside down..... the bleed nipples were on the bottom of the calipers (instead of the top where they obviously have to be, to bleed air succesfully)....

[naten]

Thats how i bled them, unless air is trapped in the MC i didnt bench bleed it first. I cant see it being the issue as ever car/friend that i know of hasnt done it.

Calipers are on the right way bleed nipple at the top, didnt even think about it when putting them on

Eldar did u bench bleed yours first? my MC is a hilux one as well.

[wa5]

That was going to be my next Question, is the M/C of a suitable size to suit the upgraded calipers?

IE is your Master Cylinder the right Hilux model to suit your application? (if that is what is recomended by other who have done the same conversion)

[M.J.H]

I have always bench bleed the master cylinder before fitting to the car
if you didn't try loosening the nuts what hold the pipes into the cylinder and see if you can get any air out of there.

Have you driven the car with the brakes as they are? I fitted new pads and M/C to a car once and bleed new fluid through several times as the guy pushing the pedal was adamant it felt like it had air trapped in the system somewhere as the pedal was spongy. Took it for a drive and was okay till the pads bedded in and the pedal feel got a whole lot better after that.

I also recall a thread on here or the old forums with the same sort of problem you describe.
In short the way the caliper was angled was holding air even after several attempts to bleed them. They had to pivot the caliper so it was straight up and released all the air that way. maybe worth a try for your setup as well.

EDIT Found the thread
http://www.toymods.net/forums/showth...leeding+brakes

[oldeskewltoy]

I no longer bench bleed master cylinders(Toyota type).
1) I install them, lay the threaded brake hose into the fitting but do not tighten other than catching a thread or two
2) fil the master cylinder
3) using the palm of your hand "pump" the top of the master cylinder. The fitting closest to the resevior will flow first. tighten this fitting. Pump with your palm some more till the further fitting flows.

DO NOT BOTTOM A TOYOTA master cylinder! Everytime I've done it... or I've heard it done... the EXACT problem you describe occurs.

You need good communication and someone who doesn't slip off the bleeder (2 person bleed).

You can use a pressure, or power blleder to run the fluid through... but I STRONGLY recommend a good pump bleed as well. The power bleeders can NOT equal the pressure that you can build with the master cylinder.... just be careful not to bottom it out!

[wa5]

Obviously bottoming the M/C out causes a problem? can you expand on that a little... Does one of the rubbers get stuck? and what is the solution/ cure?

[amichie]

Have you bled the rears also??

[naten]

numerous other people have done the brake upgrade i did without and problems, the piston size and MC bore size are almost the same.

Rears have been bled every time with the others.

"DO NOT BOTTOM A TOYOTA master cylinder! Everytime I've done it... or I've heard it done... the EXACT problem you describe occurs." What does that do? cant see it being a huge issue if its a new MC? And the solution if that occurs?

Ive driven it a little like just round the block and it brakes kinda ok but the pedal is far too low as described.

I read through that thread and what happened to peewee wouldnt be my issue as my calipers are near vertical.

[oldeskewltoy]

Obviously bottoming the M/C out causes a problem? can you expand on that a little... Does one of the rubbers get stuck? and what is the solution/ cure?

ANOTHER master cylinder....

My expereince is with AE86s... but it is quite a bit... both personel*, as well as advising others and them finding out the same thing.

I'm not sure WHY??? Anyones guess is as good as mine is... I've just learned that you bottom it out and you get this little non existant air leak that keeps the system just spongy.....

replace the master with an Aisin(oem unit) and bleed it 2/3 of a stroke MAXIMUM...


* - Not 3 weeks ago... I updated to new rear calipers... Goodridge SS lines. A friend and I got it bleed just right... hard pedal running and off. We went to bleed it one last time to just see if the pedal would change............. he slipped off the bleeder... my foot went stright to the floor... and it was junk. I got a replacement... and this time I was at the bleeder... no slips this time... brake pedal is hard and fine with a new master cylinder

["Z" UTE]

If the brakes seem to be OK, not spongy, but pedal is low. Then have you thought about adjusting the pedal height in the cabin?

cheers Chuck.

[naten]

ok just gave it another crack

bled all corners 4-5 times in correct order going through 500mls of fluid

technique was got the mrs to pump up the pedal till hard, i released the nipple and then closed it off before it got to the bottom. NO air come out at any point in doing this.

result, no better. I can still pretty much hit the floor with the pedal when running

oldeskewltoy: To be honest i cant see a new MC being toast if you push it the full length when bleeding and not being able to fix that? Did you try to bench bled any of them after it happened?

[naten]

just had a look tis already adjusted all the way out too
so the pedal is at its highest/will have most push.

[naten]

ok ive isolated the problem down thanks to some advice from robs old man

Seems the drivers front caliper is causing the issues. If i clamp the brake line going to it the pedal gets hard when its running. Something it doesnt do if its not clamped

Thing is, i have NFI how air could still be in there. I have now taken the caliper and disc off together and bleed them at all the angles under the sun and no extra air has come out.

No leaks are visible, i cracked the caliper apart just to double check the seals between the two parts and all was well there.

So now im stumped.

Only thing i found on the net was a bloke had a similar problem with a 240sx and he 'reverse bled' the brakes. Dont know what this is but i might have a look and give it a go

[Dale]

How old are the lines? They might be swelling, look for bubbles in the flex line

[naten]

na new lines