Final bug in brake system, then back on the road.

If I don't press the brake pedal for a few minutes, the first time I press it it goes almost to the floor. If I press it twice, it firms up quickly.

I don't want to drive it like that.

I loosened the brake lines at the master cylinder, and had the wife pump it a couple times to squeeze out any possible M/C air. It was fine.

Bled brakes from farthest tire and worked my way to closest tire to MC, and on the passenger front, I got several pumps of foamy bubbles. Everything else was clear and bubble-free.

Still has that first soft pump.

Any suggestions for going onward from here?

All new lines from master cylinder to new front calipers. Lines are new from rear splitter at differential to new rear calipers.

Do I just need to keep bleeding because of all the new lines?

 

Well...You can pinch off the brake hoses and see if it still is soft on the 1st pump...If so the M/C is no good. Or you may need a residual pressure valve in the line/lines to the rear calipers. The auto manufacturers did this to combat the problem you are experiencing. Or...You stillhave air in the lines someplace....You dont have any calipers with the bleeder on the bottom instead of the top right??? That would be bad.

 

What is residual pressure valve? Had drums in back, and now disks, so maybe this is my issue???

The M/C is new in December 09 Wilwood. Never been dry. Doubt it could be the issue. Probably have 500 miles driving on it since installed.

 

the residual pressure valve, if you have them, is located in the master cylinder, in each chamber. they're used on drum brake systems to keep some pressure in the line after the pedal is released.
what brake combination was this m/c designed for?

i doubt this is the issue though, it sounds more like air in the system to me.

 

M/C is Wilwood 260-8555-P

From Jegs "High-pressure die casting of a premium alloy produces a high-capacity body that is lightweight, looks great, and has the durability for competition that you expect from Wilwood Brakes. A black anodized, machined billet lid captures a pressure balanced bellows gasket with 100% sealing against moisture invasion or fluid leakage. The mounting flange is slotted to accommodate installation on bolt centers between 3.22" and 3.40". That makes it a simple bolt-on to many OE mounts including the popular Chrysler, Corvette, GM, and Ford Mustang master cylinder bolt patterns.

The body also features two through-hole mounts on 6.40" centers for side mounting to frame members or other secure elements of the chassis. Each master cylinder is configured with full separation between the front and rear reservoir chambers and fluid outlets. There is pressure access on both sides of the piston bore for right or left hand plumbing based on mount location. A total piston stroke of 1.10" is distributed at a 2:1 volume ratio between the primary and secondary chambers. A choice of 7/8", 1" or 1-1/8" bore sizes provides the necessary options to match the volume and pressure requirements of nearly any application. And for those wanting a show car look, a bright finish, media burnished version is available and guaranteed to catch the eye of the most discriminating enthusiasts."

Nothing about residual pressure valve.

I am a newb at brakes, so any help would be appreciated.

 

It worked firm and hard with rear drums and stock front disks, and still firm after front disk upgrade. Seems like after I added the rear disks, it all went downhill.

So, does this valve hold pressure in the rear calipers, so it doesn't all bleed out after the brake is let off? If so, this sounds like exactly what is going on here.

 

I have seen some rear brakes that need to be adjusted out by pumping the e brake a bunch. The piston may need to come out more.

 

Sounds like your master cyl is too small of a diameter..... Disc brakes require more fluid to move the piston the the small diameter wheel cylinders in drum brakes do, when you increase the amount of fluid require to move the piston it makes the pedal lower.....

By the part number your master is a 1" diameter, I usually use a 1.125 diameter master..... Also as mentioned earlier a residual valve will more then likely help your problem.....

Here is a wildwood 2lb residual (http://www.jegs.com/i/Wilwood/950/260-1874/10002/-1), it says in the description they are used when the master is lower then the brakes..... But I have seen them help even when the master is in the normal position which is higher then the brakes..... You can put one in both front and rear brakes, they go in line preferably as close to the master as possible..... They hold a very small amount of pressure on the brakes(2lbs isn't much, but it helps keep the pistons/pads closer to the rotors)..... They effectively do the same thing as your first pump that get the pads up against the rotors.....

 

Hmmm...good info. I will have to look into this next step in my snow-balled project!

Thanks for the part number and everything!!! Makes my life much easier!

 

2# valves are for rear disc setups...10# are for rear drum setups. Do you have an integral parking/E brake on the rear calipers.(the cable goes to an arm on the caliper) If so...Pull the e brake...Step on the brake pedal...Release the e brake. Do this 3 or 4 times and it will set the travel/preload on the rear pads and you should be golden. Or as Frank said, you may not have enough volume with the M/C and rear disk set up... Residual valves will help but, you should go to a bigger bore M/C if this is indeed the issue. Good luck Scott, hope you nail it down quickly.

 

Scott


You sad you have bubbles at the right front after you pump 2 or 3 times ???


Are you pumping the pedal 2/3 times and holding the pressure before you open the bleeder ?????

If you are getting air at that point you need to check all you fittings in the front system you maybe sucking air through lose fitting.

The next thing you need to check on you may need a disc / disc master.

 

Will try this after work, and see if I can get by without the valve or a new M/C.

I really need to get to a point where I don't have to spend any $$$ each time I get in that car...

 

maybe try getting into the car parked next to it...

 

I had the same issue when I swapped to 4wdb. I had air in the calipers, two of the bleeder valves were pointing down. I had to pull the caliper from the rotor and point the valve up them re-bleed them. I went through a couple quarts of fluid before figuring this out.

 

My calipers are installed correctly. In fact, the front ones have a bleeder screw on both sides so it doesn't matter which side they are installed on.

Got home and had to build a chicken coop, so never had a chance to try the e-brake trick.