ma61 spongy brakes after upgrade and many bleedings

[CrUZida]

Thats got me stumped too, unless it goes even harder when you clamp both fronts.

I gather it looks something similar to this (caliper orientation) http://conceptual.net.au/~peewee/discs/brake_done_1.jpg

[naten]

Yea looks exactly the same as that, going to make up a home made bench bleed kit for the MC this arvo will see how that goes

[sleeektoy]

My brother had the same problem with his AE86, it was a long time ago though

I think the issue was resolved with the engine running(vacuum on the booster) and bleeding the brakes using a "suck" type bleeder at a local mechanic that bled from the caliper using a vacuum arrangement drawing the fluid through without pumping the pedal.

Something to do with the master cylinder and brake booster arrangement.
I have no idea why this method worked but it made a massive difference to the pedal firmness.

[takai]

Last time i had a problem like this it was because the diaphragm in the booster had ripped.

[GT1978]

Last time i had a problem like this it was because the diaphragm in the booster had ripped.

Would have thought this would have given firmer peddal as you would lose the power assistance.
Last time I had this prob. was the master cylinder needed bleeding separately but we think thats been covered so my questions are;
Which lines did you replace? Just the hoses or hard lines also.
If the hard lines were replaced are the front and rear circuits connected to the right points on the brake bias thingy?
And are you positive all connections are up tight. Air can tend to get into joints that are too small for liquid to squeeze out.

One more thing, you say the pedal adjustment is at full length. Are you sure the master cylinder is returning fully?

Glen

[naten]

Working on it again now.

Made my home made MC bleeder and gave it a bleed. Not much air was in there to start with i must say, basically one pump and it was only fluid

one thing i did notice tho was the rear port pumps fluid before the front one, does that sound right to anyone?

Havent bolted it back on yet so nfi it it made a difference yet, will try a couple of more things while its out.

[CrUZida]

My understanding is that if both ports are full of fluid they should pump at the same time (as there is only one piston)
If the front is pumping later then it has air in it.

Feel free to correct me.

[naten]

hmmmmmm thats my understanding of it too

The rear port which pumps first is connected to the rears too which is probably why it feels hard when i clamp the fronts.

Ive pumped it maybe 30-40 times now with jump fluid coming out using a proper technique for MC bleeding like this
http://www.superchevy.com/technical/.../photo_02.html

[naten]

a mate just had an idea too that the new MC which was for a early Hilux wouldnt work properly because it has drums on the back and the supra has discs

Wondering if its normal to use these MC with the supra?

[CrUZida]

Yeah, that should be fine as long as its a 15/16th's MC.
The bias valve on the firewall does the rear adjust.

[naten]

hmmm after talking to two mechanics and reading up the on net it seems that drums require different pressure to discs.

They also have a check valve built into the MC to keep pressure on the drum when you release the pedal, which is not wanted for discs. IT also explains why the MC pushes fluid to the backs before the fronts and at a higher volume

The brake place i bought it from is calling me back tommorrow so ill ask him then. But it seems the most logical thing to me so far.

[naten]

btw im off to melb for 4 days so i wont be able to post in that time, just so u guys didnt think i was loosing interest or anything

[rob]

Yeah, that should be fine as long as its a 15/16th's MC.
The bias valve on the firewall does the rear adjust.

this is my experience with celica corolla corona supra cressida as well, BUT but looking at a hilux yesterday there was no proportioning valve on the fire wall

rear line goes to rear of the hilux and T's off somewhere around the diff
the front line splits into a 3 way, 2 go to each front and one line goes to back of the hilux wtf?

no proportioning valve on the firewall

which makes me suspect the master cylinder does this internally

[GT1978]

If the front circuit runs off towards the back of the car also I'd reckon the proportioning valve is mounted back there too. Follow the line if you can and see where it goes.

[thechuckster]

rob: A hilux will have a limiting valve at the rear of the ute - it's mounted to the frame and has an arm on it that goes down to the diff. It changes amount of rear brake pressure based on load (e.g. ride height).