Signs Of A New Master Cylinder
09-05-2006, 08:59 PM
#1
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Vehicle: Two 97 RD Tibs and 2010 Genesis Coupe
As many of you know i have a 4 piston Willwood brake kit front and rear and since the install it has been about 1000K on the car and i cant figure out why the brake pedal feels spongy and slowly sinks with a bit of effort on your foot.
We have bleed the car 3 times and went through 2 bottles of Brake fluid and still nothing....
I also had a NEW OEM master cylinder installed BENCH Bled the MC and then also bled it on the car and redid the calipers all around the car again and still a spongy pedal which after afew pumps hits the ground with some force....
In the process you can see the MC flxing about 1/2 inch but some flex is NORMAL but i was thinking of fabricating a bracket to the chasis to Support the MC from Flexing ..This should enable my braking to be more sensitive but i dont think it will fix the spongy pedal at idle...
Also i have no leaks whatsoever.....
I was wondeirng if it can be my stock proporting valve thats causing it but i dont think because it never did this before my Brake Upgarde....WEIRD cool.gif
Any one have any ideas or anyone that has a BBK installed has the same problem
Thanks!
We have bleed the car 3 times and went through 2 bottles of Brake fluid and still nothing....
I also had a NEW OEM master cylinder installed BENCH Bled the MC and then also bled it on the car and redid the calipers all around the car again and still a spongy pedal which after afew pumps hits the ground with some force....
In the process you can see the MC flxing about 1/2 inch but some flex is NORMAL but i was thinking of fabricating a bracket to the chasis to Support the MC from Flexing ..This should enable my braking to be more sensitive but i dont think it will fix the spongy pedal at idle...
Also i have no leaks whatsoever.....
I was wondeirng if it can be my stock proporting valve thats causing it but i dont think because it never did this before my Brake Upgarde....WEIRD cool.gif
Any one have any ideas or anyone that has a BBK installed has the same problem
Thanks!
09-05-2006, 09:24 PM
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Vehicle: 1997 Tiburon
Rob, I have an idea.
You ship me your rear setup, and I'll ship you drum brakes. Than your MC will have no problem with the load smile.gif
I think you need a bigger MC man. You have a BIG setup. The stock MC was not engineered for your extreme setup.
Maybe...open the hood, look at it..flex..than see if it works LOL
You ship me your rear setup, and I'll ship you drum brakes. Than your MC will have no problem with the load smile.gif
I think you need a bigger MC man. You have a BIG setup. The stock MC was not engineered for your extreme setup.
Maybe...open the hood, look at it..flex..than see if it works LOL
09-05-2006, 09:25 PM
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you are using both bleeder valves on the calipers, right?
and yeah dude, get a new master cylinder...
http://wilwood.com/Products/006-MasterCyli...-CRMC/index.asp
(no clue which one, email wilwood and see what they suggest with the calipers you have)
and yeah dude, get a new master cylinder...
http://wilwood.com/Products/006-MasterCyli...-CRMC/index.asp
(no clue which one, email wilwood and see what they suggest with the calipers you have)
09-06-2006, 12:36 AM
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only other thing i can think of is, i stripped out the bottom bleeder screws on my calipers and never noticed they were leaking a small amount of fluid, i drove on it for liek a day before i saw the inside of my wheel
09-06-2006, 12:18 PM
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also, how exactly are you bleeding each caliper? one bleeder valve at a time? from wilwood's website...
QUOTE
To properly bleed the brake system, begin with the caliper farthest from the master cylinder. Bleed the outboard bleed screw first, then
the inboard. Repeat the procedure until all calipers in the system are bled, ending with the caliper closest to the master cylinder. If the
caliper is fitted with bleed screws on four corners, make sure the bottom bleed screws are tight. Only bleed from the top bleed screws.
NOTE: When using a new master cylinder, it is important to bench bleed the master cylinder first.
the inboard. Repeat the procedure until all calipers in the system are bled, ending with the caliper closest to the master cylinder. If the
caliper is fitted with bleed screws on four corners, make sure the bottom bleed screws are tight. Only bleed from the top bleed screws.
NOTE: When using a new master cylinder, it is important to bench bleed the master cylinder first.
09-06-2006, 03:56 PM
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Tanc Nice try bro nana.gif
Tibby!
Basically it was bled 3 times all around the car using the top 2 Bleeder valves for each caliper.My guy started from the furthust caliper and then worked around th ecar.
He also Bench Bled the new MC and also was Bled on the car.
What im thinking of doing this week is actually diconnect both lines going in the MC and cap them up..
If the pedal still feels spongy and slowly sinking to the floor then its a bad MC.........
If it still does it then im thinking its the STock proportaning valve in the car.
Or the BOOSTER but i wonder how to test for a bad Booster or Por Valve..........
Also i did speak to Willwood and they say the stock 7/8 Bore should be Good enough for my Front and rear brake upgarde BUT if i had to upgrade a 1inch bore would be the max.....
He said this wont fix my Spongy pedal...
He also said the stock 7/8 would work better than a 1 inch because with a 1 inch bore it would make the pedal harder with more pedal travel.......With the 7/8 ther eis LESS travel
But my Machaic thinks IT might because running a larger MC will ahve less efford to move the Fluid as opposed to my Stock one which is smaller and is probably forcing itself................. sad.gif
I just dont want my brakes to fail on the road if thi sis happening and lik ei mentioned while driving th ecar stops good,Just at idle the spongy pedal and slowing sinking to th efloor when applying little force....
Tibby!
Basically it was bled 3 times all around the car using the top 2 Bleeder valves for each caliper.My guy started from the furthust caliper and then worked around th ecar.
He also Bench Bled the new MC and also was Bled on the car.
What im thinking of doing this week is actually diconnect both lines going in the MC and cap them up..
If the pedal still feels spongy and slowly sinking to the floor then its a bad MC.........
If it still does it then im thinking its the STock proportaning valve in the car.
Or the BOOSTER but i wonder how to test for a bad Booster or Por Valve..........
Also i did speak to Willwood and they say the stock 7/8 Bore should be Good enough for my Front and rear brake upgarde BUT if i had to upgrade a 1inch bore would be the max.....
He said this wont fix my Spongy pedal...
He also said the stock 7/8 would work better than a 1 inch because with a 1 inch bore it would make the pedal harder with more pedal travel.......With the 7/8 ther eis LESS travel
But my Machaic thinks IT might because running a larger MC will ahve less efford to move the Fluid as opposed to my Stock one which is smaller and is probably forcing itself................. sad.gif
I just dont want my brakes to fail on the road if thi sis happening and lik ei mentioned while driving th ecar stops good,Just at idle the spongy pedal and slowing sinking to th efloor when applying little force....
09-06-2006, 04:17 PM
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dude, check out the brake troubleshooting on webtech. im sending you an email with it now to your sympatico addy.
you did finally get the fronts to lock up before the rears right?
you did finally get the fronts to lock up before the rears right?
09-08-2006, 06:35 AM
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Tibby
Ya i got the front to lock up first..
I did about 5 test runs while dricving about 100klm or 60 MPH on a staright road and then slammming on my breaks..Car stops staright....
On 2 of the runs while doing the same test it did slightly pull in the rear driver side a bit..
But i spoke to willwood and they said sometimes its normal that it does that.
Also i do have two pro Valves for the rear hooked up which are turned off completely.....I was told from Willwood with the valves fully closed its at 54%..
Usually brake setups are 70% front and 30% rear so in my case i have 70% front and about 12% rear..
The way the pro valves are hooked up is that they are feedeing fron the stock pro valves and then running to the rear brakes.
I was thinking of deleting the stock pro valve and run staright hard line and see what happens.What i think might happen is that the spongy pedal and sinking might be gone if i do this becausre i already have a pro valve from Willwood and maybe the stock pro valve is interfering..
Not sure but i might try..
Today im gonna do my MC test where i plug the lines and see what happens...
Ya i got the front to lock up first..
I did about 5 test runs while dricving about 100klm or 60 MPH on a staright road and then slammming on my breaks..Car stops staright....
On 2 of the runs while doing the same test it did slightly pull in the rear driver side a bit..
But i spoke to willwood and they said sometimes its normal that it does that.
Also i do have two pro Valves for the rear hooked up which are turned off completely.....I was told from Willwood with the valves fully closed its at 54%..
Usually brake setups are 70% front and 30% rear so in my case i have 70% front and about 12% rear..
The way the pro valves are hooked up is that they are feedeing fron the stock pro valves and then running to the rear brakes.
I was thinking of deleting the stock pro valve and run staright hard line and see what happens.What i think might happen is that the spongy pedal and sinking might be gone if i do this becausre i already have a pro valve from Willwood and maybe the stock pro valve is interfering..
Not sure but i might try..
Today im gonna do my MC test where i plug the lines and see what happens...
09-10-2006, 07:11 AM
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Update
Well we did you a MC test today where you plug up the two holes in the master and the end result was the brake pedal was HARD which is suppose to be and not spongy.
SO now i dont know where this leak can be>......... 02.gif
My guy thinks a Bigger master will solve this but WIllwood says IT wont.
hm weird cool.gif
Well we did you a MC test today where you plug up the two holes in the master and the end result was the brake pedal was HARD which is suppose to be and not spongy.
SO now i dont know where this leak can be>......... 02.gif
My guy thinks a Bigger master will solve this but WIllwood says IT wont.
hm weird cool.gif
09-10-2006, 07:45 AM
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well, couple of things. Make sure your fire wall is not flexing when you hit the brakes hard. A bracket could help this, but really the only way to perminently fix it is to do what I am doing to my fiat, reinforcing the firewall with sheet steel all around where the Mastercylinder bolts to it.
While you have the Master Cylinder diconnected from the system. Try just bolting up the lines to the fronts and see if the brake pedal sinks or not.. then do the same in the rear. Unhook the front and cap it off and hook the rears up.
Personally, I think it is a combination of flexing firewall and the fact that your master cylinder cannot push enough fluid to the brake calipers.
While you have the Master Cylinder diconnected from the system. Try just bolting up the lines to the fronts and see if the brake pedal sinks or not.. then do the same in the rear. Unhook the front and cap it off and hook the rears up.
Personally, I think it is a combination of flexing firewall and the fact that your master cylinder cannot push enough fluid to the brake calipers.