Rear Disc brake problem

[blzrgb]

I put a 14 bolt under my K5 a while back and upgraded to rear disc's.
It was originally a diesel (civi) from the factory and still has the factory hydra-boost.
I've bled the brakes both manually and with my pressure bleeder.
So I'm very confident that air is not my problem.
But, I can't get enuff fluid pressure to the rear. When you mash the brake pedal, there's way too much travel in the pedal.

Could it be the equalizer ??

Under normal driving/stopping it feels like the rears are not even getting pressure. I've done this swap several times to my other trucks without any problems. WTH ???

 

[Kain]

the rear rubber line might be cloged

 

[chevysmithz71]

This is the exact problem I'm dealing with now. The stock proportion valve is splitting 70/30 for drums. I've put in inlinetube.com disc/disc proportion valve, which splits it 50/50 and still nothing. So, I've read this whole thread and there are some ideas here.
http://coloradok5.com/forums/showthread.php?t=174038

Seems the 99 c3500 master only works for the 80's trucks.

 

[blzrgb]

What's weird is I did this exact same swap to my cucv and it has awesome brakes. Stainless braided lines and Hydra-boost. They both have the same
MC. It's GOT to be either MC or equalizer block. I guess.

 

[sweetk30]

we had a member few years ago same problem .

finaly gave up and posted pics and we still didn't get it .

he took to a local shop and the mechanic spotted it right off.

he had a calipers on the wrong sides and the bleeder screws were pointing down . flopped them side to side and blead the system and drove it home perfect.

 

[Blue85]

You will generally have more pedal travel with discs than you did with drums, just because the piston is so much bigger. The smaller the rear caliper piston, the less pedal travel you will have. For troubleshooting, you might try clamping the rear soft-line with vice grips to see if your pedal comes up. Is the stock combo valve still in there? Those sometimes hold off on front pressure until a certain amount of rear pressure is seen. However, the combo valve can be partially gutted. Have you skidded the truck on gravel/mud? Can you lock the rear at all? What rear calipers are you using? Rumor has it that parking brake calipers have to be adjusted right for the hydraulic brakes to work right.

There are lots of places for air to hide, like inside the combo valve or in re-routed lines. Sometimes driving around can lodge things loose with air coming back to the MC. Did you replace or relocate any components other than on the rear axle?

If you are bleeding fluild from all 4 corners, the lines are probably clog-free. If you are not bleeding all 4, you may be missing air caught in the front circuit.

 

[blzrgb]

The kit came from ORD. Same as the cucv with no problem. I cant pinch off the rear soft line because I used all stainless flex. Is it unheard of to
by-pass the combo valve ?

 

[wasted wages]

As said above... Make sure your bleeders are pointing straight up....even if you have to take them off and put a piece of plywood in as the rotor....that way you can still pump them up and bleed them with a second person pumping up the brakes.

Also if they are caddy calipers, you DO need to adjust them manually prior to bleeding them to get the best pedal... I have them on my 79 Ford pickup with a D60 rear and can lock the brakes at all 4 corners and have a high pedal.

All with the stock M/C and prop valve......

 

[sweetk30]

on my old truck I removed the prop valve.

installed a tee fitting for front lines .

then adjustable valve for the rear .

few test drives I got a bias I liked .

http://www.summitracing.com/parts/sum-g3905/overview/

you will need 2 new fitting for the valve to go to 1/4 line and not the 3/16 line fittings provided in the valve kit .

I made a little bracket and mounted it to the master/booster 1 of 2 studs to keep it high / dry in the engine bay area.

 

[chevysmithz71]

on my old truck I removed the prop valve.

installed a tee fitting for front lines .

then adjustable valve for the rear .

few test drives I got a bias I liked .

http://www.summitracing.com/parts/sum-g3905/overview/

you will need 2 new fitting for the valve to go to 1/4 line and not the 3/16 line fittings provided in the valve kit .

I made a little bracket and mounted it to the master/booster 1 of 2 studs to keep it high / dry in the engine bay area.

This is exactly what I was looking for. Thanks

 

[blzrgb]

on my old truck I removed the prop valve.

installed a tee fitting for front lines .

then adjustable valve for the rear .

few test drives I got a bias I liked .

http://www.summitracing.com/parts/sum-g3905/overview/

you will need 2 new fitting for the valve to go to 1/4 line and not the 3/16 line fittings provided in the valve kit .

I made a little bracket and mounted it to the master/booster 1 of 2 studs to keep it high / dry in the engine bay area.

Once you installed this, did it help to bring the brake pedal up off the floor ? In other words, did you have a firmer pedal ? With mine biased as they are, my pedal is very low to the floor when you mash it.

 

[sweetk30]

should have mentioned I had hydro boost and 1ton master swaped also .

low pedal is 1 of 2 things . air in system or to small a master for the volume needed in fluid movement .