ma61 spongy brakes after upgrade and many bleedings

[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

[M.J.H]

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

I had a problem like that on a car not long ago.
Apply brakes and same sort of symptoms as you describe so was isolated to a problem with the left front caliper.
Had a look and could see the one of pistons wasn't staying out the few mm to keep in contact with the pad but being pulled right back into the cylinder. Removed the pads and pumped the pedal to move them all out then pushed them back just enough to get the pads back in.
Worked fine after that.

[wa5]

Does the problem disappear only with the right front caliper disconected ... have you tried disconnecting the left front instead....

What I am getting at, is this.... Are you sure the Master Cylender has enough capacity for the conversion.... Not others have done it, so its okay. Are you sure.

[CrUZida]

Z32 calipers are IDENTICAL in size to stock calipers, so the M/C is fine.

I recently had the same issue as yourself, after bleeding every caliper about 4 times and going through well over a litre of fluid I finally bled the master cylinder (pump up the pedal as per normal and crack the hard lines that leave the cylinder). My M/C was full of air even though the lines were full of fluid. After that the brakes came up trumps.

Note I've changed the brakes on maybe 1/2dozen cars including changing a couple of master cylinders and I've never had to bleed a master cylinder before.

Also note the 'do not bottom out the m/c' only applies to old m/c's that haven't been flushed, as the dirt build up in the untravelled section can rip the plunger/seal (it doesn't always happen). If its a new m/c or a freshly flushed one its fine.



But back on topic, if you think only one is dodgy, have a look at the line. I've had a time where one of the joints wasn't up tight enough, and it was weeping slightly, and I couldn't get good pedal feel. Tightened that joint up and stopped the leak and it came up trumps.

[naten]

as stated the MC size is ok.

I tried doing what you said on the car to bleed the MC no air just fluid came out. I thought maybe because the MC is at a bit an angle (the end is up a bit) that may be trapping some air in the end of it. To do this i pushed the piston in with a screw driver, let the fluid pump out and then cover the holes when i released it. I dont know how effective i was at doing it but it made no difference.

I also worked out that if i clamp either front brake lines it makes the pedal hard, so it isnt one particular caliper. Which is quite strange im trying to figure out why in my head.

One possibility is the MC isnt bled correctly but the only way im going to do any better is to buy a MC bleed kit and nowhere sells them

[naten]

also pistons are all coming out to make contact with the pads

[CrUZida]

I thought maybe because the MC is at a bit an angle (the end is up a bit) that may be trapping some air in the end of it. To do this i pushed the piston in with a screw driver, let the fluid pump out and then cover the holes when i released it. I dont know how effective i was at doing it but it made no difference.

Or you could try bleeding the MC with the car parked on a hill ?

[naten]

thats actually a good idea, im outta fluid for today so its on hold till tomorrow.

Just been mulling things over and it doesnt make sense that its the MC. If i clamp front lines (either of them) then it goes hard, which suggests its not air in the MC. Because if there was it would still be soft.

Which means its the calipers but they arent leaking and are fresh from a rebuild and full of fluid.

[CrUZida]

Does it go any harder if you clamp both lines ?

[M.J.H]

also pistons are all coming out to make contact with the pads

But are they staying out there when the pedal is released or does one or two of the pistons retract with a visible gap?

[naten]

hmmmm M J H i understand what you mean now, but from memory they didnt go back, will have to double check though.

Peewee from feel id say its the same if i do one or both, but again would have to redo it to make 100% sure.

Tis doing my head in why i can clamp either side to make it hard