ra28 w brake issues(r33 brake upgrade)

[bigmat]

brakes are staying engaged even when i lift my foot of the brake pedal. its starts of slow then cradually gets worse so the car stops without me pressing the brake pedal

what i have is r33 4 spot, willwood bias adj, ma70rear disk conv, ra28 booster, ma70 1' master.

done so far to fix problem( this has just happened and the car has been driving fine before hand)

when car is left for 10 min all goes back to normal

backed of mc from booster, car still didnt roll
jacked up car and all wheels wouldnt spin
backed of bias and car started rolling

Q is it the bias not set correctly or is it the mc
Q do i need to crack the mc to see and work my way threw to each wheel to eliviate the built up pressure

backed of the actuator valve in the booster aswell and its wound of as far as it can go

cheers mat

[bigmat]

bump anyone

[oldcorollas]

puzzling....

are any of the brake lines getting hot from exhaust?

brakes applying by themselves.. all 4 brakes.. sound slike something in the fluid boiling and giving pressure to the calipers.

how old is fluid?

bias adjuster set correctly?

if you release it all the way, does the problem still occur?

hmm... pushrod from pedal keeping the booster engaged?

[allencr]

Q do i need to crack the mc

If you opened a bleeder, front or rear, or the MC lines, it would be relieve pressure & free up, right?

MC adjustment and/or MC, OR whatever a 'willwood bias adj.' is, not so much the willwood itself, but how you've got it plumbed/adjusted.

[sheepers]

i had this same problem but not so severe,
i did two things and fixed it straight away.
firstly, the adjustment for the booster plunger is critical, it needs to have a gap (fuck all, less than 1mm) so its not depressing the master plunger at all.
and the second thing is to make a heat shield to stop your master getting hot.
when i did these two things, problem fixed.

sheepers.

[The Real Roadrunner]

it wont be a hot maso causing the problem as his turbo is on the passenger side.

Was the MC rebuilt or just thrown in as was? are all the lines new or std? has the whole system been flushed properly? does it still have the factory prop valve or is that gone?

Is the pedal hieght adjusted correctly? does it return completly? is the spring tensioned enough on the pedal? is the pushrod adjusted correctly (a little bit of slack)? is the booster rod adjusted properly (as above 1mm gap)?

Could be something complicated or it could be something piss easy to fix but without checking it over its hard to diagnose.

Did it just start happening all of a sudden or gradually? does it do it all the time or just sometimes?

if a maso is in good working order there is no way it will keep enough residual pressure in the system to hold the brakes on let alone force them on hard.

Have you tried to drive it without the booster hose connected? if you havn't try it but be aware that your brake pedal will feel like your pushing on a rock. maybe the booster is trying to hold the brakes on?


UMMMM ill think about it some more and ill give you a buzz when i have time.

Cheers
Linden

[sheepers]

it wont be a hot maso causing the problem as his turbo is on the passenger side.

ohhh yea,
hes got one of those funny engines with the turbo on the wrong side.
i forgoterised

[web]

Bias valve faulty or installed incorrectly?

Sounds as if the bias valve is blocking backflow from caliper to mc.

Especially because the brakes free up when you back off the bias.
That sounds very much like a smoking gun to me...

Any way you could bypass it and check? Of course no real driving that way, but a careful roll around the block should be enough to eliminate or confirm the bias valve as a suspect...

[wilbo666]

Yeah I'd check the "booster push rod"

http://www.cygnusx1.net/Supra/Librar.../BR/BR_021.gif


Cheers
Wilbo

[andrew_mx83]

Bias valve faulty or installed incorrectly?

Sounds as if the bias valve is blocking backflow from caliper to mc.

Especially because the brakes free up when you back off the bias.
That sounds very much like a smoking gun to me...

Any way you could bypass it and check? Of course no real driving that way, but a careful roll around the block should be enough to eliminate or confirm the bias valve as a suspect...

wat he said.

canu easily remove the bias valve from the system and see how it goes?

[Rodger]

Check the pads on both sides. Are they thinner on one end or one edge?

Swap inside pads to outside pads and take for a drive. Upon return see if there is an un-even wear pattern present on the disc and/or pads.

I had a problem with a bent stub axle on one side allowing the caliper to pull off square to the disc, which in turn binds up the piston. It effects both sides, more so on the bent side, but enough to cause the other wheel to drag.

The bigger diameter of the new disc over the RA-28 one will accentuate any misalignment problem. Also check the squareness of any adaptor brackets/caliper mounts that you are using.

Regards

Rodger

[bigmat]

i just wrote a big fucking answer and the stupid forums dropped out.

[bigmat]

will check both rods specialy booster rod

new lines and flushed

cracked mc after pressure built up. fluid pissed out of both mc lines.

brakes returned to normal with better pedal feel than when we first did them

i think mc as it wasnt recond but checked. booster works just fine

brakes come on hard after driving for about 10 min.

could it be my vacum release?

cheers mat

[sheepers]

wind the rod back as far as it will go and see what happens.
can you get your master off the booster without dis-connecting the lines? (i can so it was really easy to fuck with the push rod on mine)
cant think of anything else that would be causing this.

oh, by the way, the amount of adjustment in mine between fucked and sweet was about 0.50mm so its really touchy, at first i thought there was no pre load when i tried to "feel" if the push rod was touching the master by pushing it onto the bolts as hard as i could, i could feel nothing, but what was contacting was enough to make the difference.

hope this helps,
sheepers.