brake pedal drops half way, then gets firm...confusion
#1
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Tour de Franzia
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brake pedal drops half way, then gets firm...confusion
My brake pedal drops about half way to the floor, then gets firm and its done this ever since I swapped in the turbo. I can pump the pedal up I have Wilwood front calipers, 1.8 rears (from a junkyard), wilwood prop valve, and nothing else special.
I've changed master cylinders, bench blead the master, changed front calipers, inspected rear calipers. I tried bleeding again last night with no success. I'm thinking about reverse gravity bleeding later today.
What are the chances of 2 bad masters?
Should I get a master rebuild kit?
If the calipers aren't leaking, what else should I look for?
Could it be the booster?
This is making me CRAZY!!! I've had this problem every single time and at my wit's end. Dear Lucifer, please help me!!!
I've changed master cylinders, bench blead the master, changed front calipers, inspected rear calipers. I tried bleeding again last night with no success. I'm thinking about reverse gravity bleeding later today.
What are the chances of 2 bad masters?
Should I get a master rebuild kit?
If the calipers aren't leaking, what else should I look for?
Could it be the booster?
This is making me CRAZY!!! I've had this problem every single time and at my wit's end. Dear Lucifer, please help me!!!
#3
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Tour de Franzia
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You can pump the pedal to bleed and the pedal is rock hard and sexy, then start the car and it drops half way to the floor. I suppose have I have old/bad master cylinders.
#4
My '99 started doing this after I swapped a Sport Brake setup onto it, if you mean you push the pedal half way to the floor before you get resistance. I haven't figured out why (though it might have a lot to do with just vacuum assistance from the engine running), but braking is very strong, no loss of fluid, etc.
#6
I had a small leak at the head of the stainless line going into the caliper on the TSE kit after some offroading at buttonwillow. Didn't find it till my next track day when 9 different spots decided to leak at the same time and the brake pedal did the same thing as you're describing. The fitting on the end of the line must have made contact with something because it was tweaked and no longer air/water tight. It doesn't sound like the problem you're having, but maybe it's worth checking the stainless lines.
#8
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Tour de Franzia
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No ABS, no leaks anywhere, I've visually inspected every part and the only questionable leak lies at the "feet" of the master cylinder. I'm ready to put a stop to this because I'm tired of the chemical burns.
#11
In other words......If we say the volume of fluid that is moved by a piston in a system with one caliper is 100cc.
The old system required 50cc to get firm pedal feel. The piston has to travel x distance to push this volume.
Now you changed systems and the new system requires 75cc to get firm pedal feel. The piston has to travel a greater distance to move 75cc than it did to move 50cc. Resulting in longer pedal travel before a firm feel.
#13
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Tour de Franzia
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No one locally has a rebuild and the replacement master is $100...so I'm considering the Wilwood master if 949 has them in stock.
#20
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Tour de Franzia
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The Lotus crew reports similar issues and adjusting the pedal works. Any thoughts on pedal adjustment? The ability to build pressure at the top of the travel tells me not too...but this is a cost-free option.
Last edited by hustler; 09-24-2010 at 04:10 PM.