R32 Gtst Brake Problem (Please Have A Gander)

[H@ME]

Hey guys!

How are we all? Got. Strange brake problem please have a read appreciate good solid constructive answers.

Car: r32 gtst

Brakes: r33 callipers as rotors all around

Replaced rubber lines with braided lines

BM44 brake master cylinder.

So, we have installed brakes and lines no worries. Bled the brakes twice. Pedal still goes to the floor.

Have checked for leaks at all fittings between master and lines, steel lines to braided lines and then braided lines to callipers, no leaks.

Have bled brakes again - same problem.

Have replaced master twice (both second had options).

When you pump the brakes rapidly the fluid goes down in the master reservoir then returns to full level.

Any help would be great what on earth am I missing??

Cheers,

HAME.

[GTSBoy]

Master cylinders are bypassing. Probably from shredded piston seals. Dismantle one and have a look.

[H@ME]

Thanks mate doesn't it seem a little odd that I have tried three and all have done the same?

It does make a suck, blow sound when pressing the pedal but i think this is the seal on the booster.

[blind_elk]

I had a similar problem with 260Z stuff in a 240Z. Turned out that a rubber block inside the booster had fallen off its location. I'd start looking there.

[GTSBoy]

Masters are often killed by people pumping the pedal all the way to the floor when bleeding. I've done it myself, and seen others do it numerous times. You can get away with it on a new MC, but an old one with cruddy build up at the end of the normal travel range can damage the seals if you push past that point.

The booster idea is also possible, and has likelihood, given that it only requires 1 failure rather than the failure of 3 MCs.

[H@ME]

Hey!

Thanks for your replies! I will take booster off and inspect further.

With a faulty booster would this still cause fluid to go into the system then return (after pumping pedal 4/5 times constantly).

Brake pedal feels as if there are no brakes and there is no pressure on the pads.

When bleeding the brakes there was no pressure of fluid coming through my brake bleeder. After 6 odd pumps I open the nipple and it just dribbles not squirts.

Cheers, Hame.

[H@ME]

Any other thoughts on this?

[GTSBoy]

When bleeding the brakes there was no pressure of fluid coming through my brake bleeder. After 6 odd pumps I open the nipple and it just dribbles not squirts.

Cheers, Hame.

I hope you weren't expecting there to be residual pressure in the lines after pumping the pedal THEN going and openign a bleeder nipple? The only time fluid comes out, and teh only time you should ever open a bleeder nipple, is during the down stroke on the pedal. It is a 2 man job. Just checking.

[GTRPSI]

Did you bleed the ABS unit too if fitted?

What procedure did you use to bleed them, longest line to shortest or other way around? Did you bleed the ABS before or after the lines?

On a full open of the lines i bleed at least 4 times to be sure all the airs out.

[H@ME]

Hey man, no abs unit on this model.

Yes I bleed longest line to shortest line from the BMC -

I have bled the brakes 3/4 times - still coming up with the same problem. Really odd - fluid goes down then returns - soft brake pedal - goes to the floor.

[StevenCJR31]

I hope you weren't expecting there to be residual pressure in the lines after pumping the pedal

THEN going and openign a bleeder nipple? The

only time fluid comes out, and teh only time you

should ever open a bleeder nipple, is during the

down stroke on the pedal. It is a 2 man job. Just

checking.

No, it doesnt have to be a two man job at all

Ive gravity bleed brakes on all my cars

[Roy]

Its hard to know...but people change master cylinders and rarely have problems with soft pedals....but when people change calipers they often complain about spongey pedals. As someone posted you can damage the BC if you push the pedal all the way to the floor...but really you need to have scummy brake fluid and crap in there for that to be an issue. Its a problem for crap road cars, not generally a problem for well maintained Skylines.

So, when installing new calipers... if you are positive there are no leaks in the caliper, and by leak in teh caliper you have removed the pad, perhaps even rotor and checked no fluid is coming out the piston boots/seals then here is what I suggest you do.

Get worn pads or something similar in thickness and put them in. Pump the brakes up and give them a quick bleed with the pistons fully extended. Make sure you have dead pads or somethign same thickness in there as you dont want to push the pistons out.

So once you have fully pushed the pistons out and put pad against rotor, open the bleed nipple with hose connected, and push the pistons all the way back into the caliper. More often then not you will see bubbles. If you do....that has been your problem

Thinsg like usign old pads with the new calipers etc all hint that this may be the problem/ People that use new pads generally squeese the pistons all the way back when trying to squeeze in teh new pads and are more likely to displace any air that is sitting bhing the displaced pistons

[H@ME]

Hey, again thanks for you reply! So compete this with all sides? I just picked up a pair of r33 callipers and bolted them on so use the pads that were in there.

Will give this a go also!

[H@ME]

I just acquired another master and booster - so will install these and then revelled including pistons. That should eliminate all!!

[533 RYC]

Hamish, before installing a master cylinder, whether it be clutch or brake, you have to bench bleed the master cylinder. Did you carry out this step BEFORE installing any of the previous three master cylinders?

Fit master cylinder in a vice. I lightly clamp in soft jaws with the bolt flange against the vice, fill with fluid, then using an extension or screw driver, pump the piston until fluid shoots from the ports.

Then fit master cylinder.

Two people are better for bleeding brakes (up, down, open, close), however gravity bleeding is fine with a 1-2 pump at the end to ensure all air is out.

[Missileman]

also a pressure bleeder is easy to make if you already have a compressor

[533 RYC]

Did you get it sorted Hamish?

[jhjones]

Another thing to check is if you put the calipers on the right sides, bleed nipple at the top.