very low rear brake line pressure.KORE3& Right stuff

[SUNK69]

I have installed my Kore3 front brakes and Right stuff power booster,master cylinder and prop. valve. I am in the process of bleeding my brakes and have very little pressure when opening the rear bleeders.I went on to the front and they bled just fine.We tried pumping and bleeding 8-10 times and just can't seem to get very much fluid pressure to the rear.I am using a 1" bore master cyl. and the rear brakes are the factory drums.I suspect a bad prop valve but not sure.have any suggestions?

[Apogee]

Did you bench bleed the MC before installing? If you did bleed it, what technique did you use?

Aside from the MC, was anything else was changed in the rear system? If you wouldn't mind, please list everything that's been changed and/or uninstalled and reinstalled, either with the original components or with new ones, so that we can try to narrow things down a bit.

Tobin
KORE3

[Roadbuster]

Does your prop valve have an integrated delay valve or do you have one in the rear line? If so you need to hold down the little button to get the rears to bleed.

Jon

[SUNK69]

Yes I did bench bleed in a vise with the included tubes & fittings from Right stuff.I filled the master cyl. inserted the tube and compressed the cyl. with a screw driver until there were no air bubbles.The rear brakes were not replaced or adjusted but I did have to cut the factory line and re-flare to adapt to the proportioning valve.I have replaced the front hard lines and used a 9" booster with a 1" bore master cyl.I don't think that the prop.valve has a button to push to bleed as it is a factory style brass unit that came from Right Stuff.I have used their conversions before and never had any problems but this has got me puzzled.By the way thanks for attempting to help me.

[Apogee]

If the MC has been fully bleed and the only place the rear system has been opened is at the MC, there really shouldn't be that much air in the rear system. I usually crack the fittings at the MC when I first begin bleeding to purge any air that has entered at the top of the system. This has usually been easier and quicker than pushing those air bubbles all the way to the back of the car.

Tobin
KORE3

[SUNK69]

I'm going to try taking the rear rubber hose loose after work and work my way forward until I get pressure and if I don't get any pressure I'll know whether it is the prop valve or master cyl.The tech guy from Right stuff told me to try crimping off the rear rubber hose to see if the pedal got spongee.I don't understand why it would affect my situation since I don't seem to be getting much fluid to that point, am I thinking of this correctly.

[Skip Fix]

A buddy just had a car the rear rubber hose had collapsed on the inside doing the same thing. Barely dribble out the bleeders, Then flowed good after a new line.

[Apogee]

How old is this rubber hose? Even if they look good on the outside, they can swell internally and if old enough, begin to crumble and decompose into a mess. Using vice grips to crimp rubber brake hoses is an unwise practice as it can damage the hose...which may not matter at this point, but it's still bad form.

Tobin
KORE3

[SUNK69]

I took the master off and re-bench bled it and all is well except it almost seems to not have enough boost.I haven't ever driven a car with c-5 brakes and I'm sure the brakes need to seat in.

[Apogee]

That's great. Some MC's prove to be more resistant to bleeding than others.

Defining acceptable pedal effort is one of the subjective things in the system, but before you go and change something, make sure you've fully bedded in the pads and rotors. Some combinations bed-in faster than others, but it usually takes 200-300 miles of normal every day driving to get an even film of friction material transferred onto the rotors.

Tobin
KORE3