Plugging rear brakes

[70Uglybird]

I have a brake system that doesn't seem to want to bleed. The fronts are C5's with Custom Works hubs, the rears are Kore3 with a custom ebrake setup (uses the C5 parking brake) It has a stock booster with a wilwood tandem 1 inch MC and Willwood prop valve. I've tried a different MC and booster with similar results.



I read up on the Hydrotechs FAQ and it said to plug the rear and make sure the Master and fronts are good if you get a good pedal. Can I do that with the prop valve? If not do I need to buy plugs or something to try this test? I'm pretty sure its the rear setup but before I spend another 1200 with Kore3 I'd like to confirm.

Thanks!

Bobby

[Apogee]

First, make sure that the rear calipers are installed with the bleed screws at 12 o'clock. Assuming they are, isolating each brake circuit (front and rear) from one another Per Hydratech's FAQ's is good advice and can help you determine where the problem is, assuming that you've already properly bench bleed the master cylinder. If you haven't, then do a proper bench bleed on the MC before you go any further...I prefer to use the plugged port method, however the recirculation method has it's merit as well, but I would still verify that it's fully bleed by plugging the outlet ports when done and confirming that the pistons hydraulically lock. If they stroke at all once the seals cover the compensator ports in the reservoir, then there's still air in the MC.

The prop valve cannot "plug" the rear circuit, only reduce the pressure output to 57% the front line pressure, so you'll need actual plugs for your MC if you intend to go this route.

Tobin
KORE3

[70Uglybird]

Hey thanks Tobin, plus I just reread my post, I'm in no way at all blaming Kore3 for this. Products and advice are top notch I'm more worried about the added C5 parking brake that is not part of the Kore 3 Kit. I would Happily pay for the parking brake kit from Kore3 if I confirm that is my problem!!! Well happily is probably too strong of a way to put it, I should have bought it in the first place. I'll pull the master out and bench bleed it again and then go through the traditionally bleeding myself then start plugging circuits per the Hydratechs instructions if needed.

Thanks for the help.

[Apogee]

No worries. The parking brake is a stand alone system from the disc brakes, so one shouldn't impact the function of the other really, at least not hydraulically speaking. You can have fully functional brakes without a parking brake at all, so while we're more than happy to sell you our parking brake solution, I don't think that has anything to do with your bleeding issues.

Tobin
KORE3

[70Uglybird]

Yesterday I had a friend come over and we bleed the master and each line. It seems like we have crazy brake pressure. With the car off after the bleed it will only have an inch or so of travel and become very stiff, seems like OK we got it. Start the car and drive it. Mushy pedal and takes forever to stop. I've had two professionals look at it and I've got some time into it. Three different masters, 2 different boosters, I'm not sure what to do here I have brake fluid all over the place The master is at a crazy angle in the 2nd gen but in an hydraulic setup I'm not sure that should matter?

[no go nova]

Did you bench bleed the master?

[70Uglybird]

The guy who tunes my car came over and bleed the master, but now I'm in the process of taken it out and ordering the kit to bleed it like the wilwood video shows. I'm also going to buy plugs for it to test each circuit. Hopefully that will identify any leaks and I can replace the lines. There are some fitting adapters the shop used which I view as potentials for leaks. I'm also going to buy the tool that measures the push rod length between the master and booster. Whats crazy is I have a pretty good sized cam in there with little vacuum I would have thought my pedal would be hard to press even with air in it.

[MonzaRacer]

If its hard without booster operating then lots of travel and mushy you MIGHT require 2 psi check valves in the front or rear lines. The allow the calipers to be out further. Most cars ,if runnign them run 2 psi on disc and 10 psi on drum brakes. The trick is that while all calipers seat the square cut seal at an angle and let the seal pull the piston back most will pull back too far, also they are used on brake systems with master cylinder setting like on frame level.
Doesnt seem like much but a friend had old school wilwood race brakes and had pedal issues for years, well towards end of season of drag racing and nearly eating dirt nbarrier he started trying different stuff to "fix" issue. Nothing worked so he put it all back together then I came over and had 2 of them in my box. I had worked on a guys show car and we only needed 2 so he gave me the others. My buddy had a ver nice area where we swapped out the line union and tada perfect brakes. They kept piston out just enough, other wise he would really pump the crap out of them.
Later we also added some distance from pedal pivot to give better mechanical leverage, after he went to lesser engine and added booster back in cause of knee issues it needed less leverage.

[70Uglybird]

Just wanted to give an update, I still have some issues but the car is definitely drive able and can take it anywhere. When I initially tested the vacuum it was at 10-11hg after getting the car back with a new motor. I installed a torquer II and Holley 850 the timing was way off. Advanced it quite a bit and now my big cam seems mild and with vacuum the brakes are working! Still a weird pedal and I'm going to have to figure something out before I ever get it on a track but for driving around its great the tires will lock up rather easily but there is decent feedback and you can control it. Just wish there was a more linear feel so manual brakes may still be in my future.

What had me stumped is I thought I would have a hard pedal without vacuum. It was really soft and wouldn't really stop the car, with vacuum the pedal is still a bit soft, but it clamps hard with very little pressure.

Thanks for all the help this has been quite the journey.