I have a new build with Wilwood four piston discs both front and back (IRS) and have a spongy and very slowly sinking pedal. I bled the brakes (DOT 3-4 synthetic) and had a couple leaks and some weeping I gradually stopped. I now have a pedal that is a little spongy and that drifts a little to the floor. I have no fluid leaks I am aware of. I figure I just need to bleed the brakes again but because it is so difficult thought I would ask here for a second opinion.
It has been my experience that any spongy feeling is air in the system OR a leak. I don't know how your calipers are mounted but you may have to take them loose, One at a time, and bleed them with the bleeder facing up. You probably already know this. Start at the farthest away from the MC and work to wards it. You may need a buddy to help hold the caliper while you apply pressure. To check for a leak Pump the system up and wedge a 2X4 or something between the pedal and some thing solid and let it sit. Comeback and hour or so later and see if you got any drips. Good Luck
Good advice. I have a double master cylinder with one line to the front and one to the rear. No, I didn't know about possibly removing the calipers and tipping up and sure hope I don't have to. Thanks.
Since you have given us very little info on the rest of the sytem I will ask the obvious. Is the m/c under the floor, or on the firewall? Floor mounted requires 2 psi residuals. Don't know what the m/c is but is it the correct bore size, and is the correct end of the cylinder feeding the correct end of the car? Is it a factory prdal ***embly or something you created? All this makes a difference.
Gradually goes to the floor?...if this is really happening, then you are getting a xfer of fluids from one cavity to another...recheck. Hold the pedal at a constant pressure and see if it goes down or not.
if the pedal is going to the floor gradually , and there are no leaks....i say it's a bad master cylinder
6 dogs When and If you have to take the calipers off remember to keep them on the rotor just angled up so the air will go to the bleed valve
I'm ***uming that you have stainless flex hoses?? Sometimes these hi-tech systems will feel really mushy if you have rubber flex hoses that tend to swell/balloon slightly which will cause a spongy pedal.
Wow--sorry I left stuff off...I was trying to get to work and forgot. I have the Wilwood dual master cylinder pedal mounted high on the firewall. One cylinder goes to the back brakes the other to the front. I have stainless lines and the stainless flex hoses. I have no residual valves. Everything is new and correctly ordered from Wilwood tech dept. Good flares and I generally know what i'm doing. I will block the pedal tonight and bleed the brakes again in the next day or so and try that.
I had that problem , all new Wildwood. Went from 7/8 MC to 1 in. that took care of the spongy feel pedal,
Yeah, falling pedal definately leak or bad master - spongy pedal either air or improper hydraulic or pedal ratio. Find/fix cause of sinking, then bleed,bleed, bleed. Still too spongy for you then reduce pedal ratio or go up in master cylinder size.
Did you bleed the M/C by itself before you did the rest? Do you have pedal freeplay? If you don't, most times the pedal doesn't go high enough to unmask the hole between M/C cylinder and reservoir and let "make-up" fluid in.
Good advice here. No I did not bleed the M/C. Yes, I have enough pedal space. I put a stick under the pedal last night and am going out to check soon. This thing is going to be on the oad soon if I have to work 24/7 to get it done.
M/C is usually bench bled , two ways to do it ; run hoses back into the reservoir then cycle slowly - or plug the discharge ports and use a one inch stroke dead heading the M/C -- do not bottom out for either procedure
Surprise, surprise...I kept pressure on the brake pedal overnight and found a small--very small leak where I was sure there was none. I would never have guessed that so thank you for that advice. I snugged things up and blocked the pedal again. I'll bleed later and do whatever I have to do. Actually, the pedal feels pretty good right now but want to see what else is going on.
do away with the synetic fluid go to regular fluid.My friend had a stock 69 camaro.Tried the synetic fluid could get no brakes. went to regular fluid had a good peddle
Been running synthetic fluid for 15 years in the 32. No probs. I had a few leaks when the car was first plumbed, but tightening them fairly hard took care of it. Note that when you join lines you'll do better if you use a steel fitting instead of a br*** one.
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