Damn brakes
richiekuk - 27/4/13 at 08:05 PM
Hey all.
I have just rebuilt my pedal box. I bought a new master cylinder for the fronts (0.625), and re-used the existing 1/4 for the rears.
I also had to buy a new wilwood powerlite caliper for the front left.
Basically I have bled the whole system (using a pressure bleeder) twice, and i still cant get a good pedal. I bled the rears first, bit of air, but
then just pure fluid.
Did the fronts. Outside beed nipple first, then inside. Again some air, but then pure fluid.
I did this twice, and still have a crap pedal. The car stops, but only after a long push, and then it pulls right.
The pulling right leads me to think there is air in the front left (new) calliper. But the second time i bled it no air came out whatsoever.
Ive got Cadwell Park on tuesday, and really want to get it sorted tomorrow.
Any ideas greatly appreciated.
Richie K
JoelP - 27/4/13 at 08:09 PM
Where is the brake light switch? Possibly air in the tee if its a hydraulic switch.
rdodger - 27/4/13 at 08:14 PM
New Wilwoods seem terrible to bleed. I had a nightmare with 4 of them!
In the end I had them suspended above the car and rolled them around as I bled them.
Got there in the end I think, though I haven't driven it yet!
britishtrident - 27/4/13 at 08:35 PM
With a pressure bleeder you still have to pump the pedal pump a couple of time otherwise you can get air trapped in the master cylinder.
big-vee-twin - 27/4/13 at 09:03 PM
Also make sure you bleed all four nipples on the wilwood caliper
CNHSS1 - 27/4/13 at 09:45 PM
try this trick. Was told it by an autograss racer 20years ago and it works! No idea how or why though.
depress brake pedal firmly and then jam length of wood or krooklok etc between pedal and seat base or chassis member to keep the pedal depressed.
leave overnight.
remove jamming device after 6-8hrs and pedal wil either be perfect or markedly better!
ive used it dozens of times with odd brake setups and it works every time
CNH
rodgling - 27/4/13 at 10:05 PM
quote:
Originally posted by CNHSS1
try this trick. Was told it by an autograss racer 20years ago and it works! No idea how or why though.
depress brake pedal firmly and then jam length of wood or krooklok etc between pedal and seat base or chassis member to keep the pedal depressed.
leave overnight.
remove jamming device after 6-8hrs and pedal wil either be perfect or markedly better!
ive used it dozens of times with odd brake setups and it works every time
CNH
Presumably you are supposed to wait 8 hrs, then crack and re-tighten the bleed nipple, then release the pedal?
richiekuk - 27/4/13 at 10:35 PM
quote:
Originally posted by rodgling
quote:
Originally posted by CNHSS1
try this trick. Was told it by an autograss racer 20years ago and it works! No idea how or why though.
depress brake pedal firmly and then jam length of wood or krooklok etc between pedal and seat base or chassis member to keep the pedal depressed.
leave overnight.
remove jamming device after 6-8hrs and pedal wil either be perfect or markedly better!
ive used it dozens of times with odd brake setups and it works every time
CNH
Presumably you are supposed to wait 8 hrs, then crack and re-tighten the bleed nipple, then release the pedal?
I was thinking the same thing.
CNHSS1 - 27/4/13 at 10:54 PM
nope, just try it, it sounds odd but it does work
if you try it what have you lost?
i used it a lot on small scimitars that have 2 bleed nipples per caliper using metro calipers and drum rears. System is notoriously bad for
bleeding.
ive usedit on AP race calipers F&R on racers too and my TVR and MG and so on.
rodgling - 27/4/13 at 11:55 PM
OK... so if there is trapped air in the system, where does it go then, if you don't crack the bleed nippple?
richiekuk - 28/4/13 at 08:40 AM
quote:
Originally posted by big-vee-twin
Also make sure you bleed all four nipples on the wilwood caliper
I thought only bleed the top 2 nipples.
richiekuk - 28/4/13 at 12:42 PM
Well after 2 more bleeds, using all the advice given. I know have what I deem to be a good pedal. Only issue is, under hard braking the car pulls
violently to the right.
Now the new front caliper Is on the left. Was wondering if there is still air in that caliper. I've tried to coax more sit out, but there seems
none left!
You guessed it. I'm gonna try again!
CNHSS1 - 28/4/13 at 01:34 PM
quote:
Originally posted by rodgling
OK... so if there is trapped air in the system, where does it go then, if you don't crack the bleed nippple?
not a f-ing clue as per my first post!!
if you don't like it don't use it, but its been used by loads of racers I know, from circuits to hillclimbs to autograss (original source),
but hey ho, cant be arsed to deal with keyboard warriors, ive offered advice that's very likely to remove the issue, your call whether its tried
or not, but no more dumb ass questions 
think of it this way, I don't understand women but doesn't stop me being married...
richiekuk - 28/4/13 at 01:46 PM
quote:
Originally posted by CNHSS1
quote:
Originally posted by rodgling
OK... so if there is trapped air in the system, where does it go then, if you don't crack the bleed nippple?
not a f-ing clue as per my first post!!
if you don't like it don't use it, but its been used by loads of racers I know, from circuits to hillclimbs to autograss (original source),
but hey ho, cant be arsed to deal with keyboard warriors, ive offered advice that's very likely to remove the issue, your call whether its tried
or not, but no more dumb ass questions
think of it this way, I don't understand women but doesn't stop me being married...
I've done similar things with motorbike front brakes. I have tie wrapped the front brake lever to the grip, and left it overnight.
I think brake fluid reservoirs are designed to let air out and not in, so after 8 hours the air bubbles rise to the highest point (reservoir), and
effectively bleed themselves.
Believe me I am hunting around the unit trying to find a suitable device for doing this tonight!
Richie K
CNHSS1 - 28/4/13 at 02:44 PM
hope it works for you fella 
its got me out of the brown stuff a few times the night before an event 
richiekuk - 28/4/13 at 02:49 PM
Can't stop it pulling violently to the right under heavy braking!
I am stumped!
britishtrident - 28/4/13 at 03:46 PM
quote:
Originally posted by richiekuk
Can't stop it pulling violently to the right under heavy braking!
I am stumped!
That is a calliper fault nothing else will cause that.
On the side opposite it is pulling towards:
(1) Check the pads move freely in the calliper.
(2) Check the pistons in the calliper are moving freely when pumped out.
(3) Check the calliper alignment with the disc the calliper must near perfectly aligned with the surface disc
As you are getting fluid through to all the callipers it cannot be a faulty braided hose, although it is far from unknown fault usually due to
faulty end fittings.
rusty nuts - 28/4/13 at 03:49 PM
Did you check that the new caliper was the same as the old one, especially the piston diameter.
CNHSS1 - 28/4/13 at 03:50 PM
not sure on the particular setup, but be worth checking the dims of the pistons in each caliper, not the first time ive seen 'odd' calipers
on either side!
edit
just re-read orginal post. As they are powerlites, they defo do differing piston sizes, if you have odd L to R, thatll defo causes your symptoms
[Edited on 28/4/13 by CNHSS1]
richiekuk - 28/4/13 at 04:32 PM
I just took the LH side apart, and there was a layer of slippery stuff covering the disc, and the backs of the pads were wet.
I cleaned everything up, rebuilt and pumped the pedal about 5 times. Took it all apart again, and there seems to be fluid leaking past the pistons on
one side of the LH (new) calliper.
Awesome, these Wilwood callipers seem to be nothing but expensive crap!
phelpsa - 28/4/13 at 05:30 PM
quote:
Originally posted by CNHSS1
quote:
Originally posted by rodgling
OK... so if there is trapped air in the system, where does it go then, if you don't crack the bleed nippple?
not a f-ing clue as per my first post!!
if you don't like it don't use it, but its been used by loads of racers I know, from circuits to hillclimbs to autograss (original source),
but hey ho, cant be arsed to deal with keyboard warriors, ive offered advice that's very likely to remove the issue, your call whether its tried
or not, but no more dumb ass questions
think of it this way, I don't understand women but doesn't stop me being married...
The air will dissolve into the fluid under pressure. It will feel good for a while but you will probably suffer a poor pedal again once the fluid
warms up and the air comes back out again!
rodgling - 28/4/13 at 06:22 PM
quote:
Originally posted by CNHSS1
if you don't like it don't use it, but its been used by loads of racers I know, from circuits to hillclimbs to autograss (original source),
but hey ho, cant be arsed to deal with keyboard warriors, ive offered advice that's very likely to remove the issue, your call whether its tried
or not, but no more dumb ass questions
Nothing dumb about my question and relax, I wasn't saying it doesn't work, just wanted to understand how. And now we've both learned
how, thanks Phelpsa.
chaddy44 - 28/4/13 at 06:56 PM
quote:
Originally posted by CNHSS1
quote:
Originally posted by rodgling
OK... so if there is trapped air in the system, where does it go then, if you don't crack the bleed nippple?
not a f-ing clue as per my first post!!
if you don't like it don't use it, but its been used by loads of racers I know, from circuits to hillclimbs to autograss (original source),
but hey ho, cant be arsed to deal with keyboard warriors, ive offered advice that's very likely to remove the issue, your call whether its tried
or not, but no more dumb ass questions
think of it this way, I don't understand women but doesn't stop me being married...
we do the same on our race bikes as well any air trapped in the brake pipes and master cylinder is allowed to return to the reservoir
depressing the pedal or lever (as on the bikes) opens up the supply hole in the master cylinder and air then returns
phelpsa - 28/4/13 at 08:52 PM
quote:
Originally posted by chaddy44
quote:
Originally posted by CNHSS1
quote:
Originally posted by rodgling
OK... so if there is trapped air in the system, where does it go then, if you don't crack the bleed nippple?
not a f-ing clue as per my first post!!
if you don't like it don't use it, but its been used by loads of racers I know, from circuits to hillclimbs to autograss (original source),
but hey ho, cant be arsed to deal with keyboard warriors, ive offered advice that's very likely to remove the issue, your call whether its tried
or not, but no more dumb ass questions
think of it this way, I don't understand women but doesn't stop me being married...
we do the same on our race bikes as well any air trapped in the brake pipes and master cylinder is allowed to return to the reservoir
depressing the pedal or lever (as on the bikes) opens up the supply hole in the master cylinder and air then returns
Thats not quite how it works. Completely releasing the pedal or lever opens up the foot valve. Depressing it will close the foot valve and hold any
trapped air in.