Soft brakes

[plyr2k]

This question was also in my previous thread, which got zero replies. Since I now have completed my disc brake install, I'll ask again

I have a 1990 k5. Dana 60/14b with discs. I used Diy4x's kit and all went smooth. Now, my brakes seem soft. With the truck off, they'll pump up solid within 2 pumps and will stay there. Won't bleed off or anything. As soon as the truck is started, the brakes become soft, and the rears will not lock up on a gravel road.

I have a feeling it has something to do with my proportioning valve and the connected block that I assume has something to do with my rear abs. Is there anyway to bypass it? Would pictures help? The brakes are bled. Then bled again. And again. There's NO air in them, and like I said, they're solid until the truck is running. I do have the stock sized master. Would a 3/4 ton master help?

Any advice is greatly appreciated.

 

[sweetk30]

should pump 1 time and be good thats first sign or not the right setup.

second yes by pass the rear abs and get rid of it not the best for our needs anyways. this gets rid of the 1 dist valve under the master with the wires going to it.

next the stock prop valve just tee's the front stright line pressure and volume. the rear part gets restricted a bit. and has the 1 tan or brown wire to dash bulb warning.

you can bypass the stock valve and do a tee in the front and stright to the rear threw adjustable vale and few test runs and dial it in. http://www.summitracing.com/parts/SUM-G3905/

or you can get aftermarket adjustable from summit http://www.summitracing.com/parts/WIL-260-11179/

also lots of guys find stock 1/2 ton master dosnt cut it for volume needed on MASIVE calipers of 1ton front and disk rear over TINY wheel cylinders in rear.

jump to a 1 ton master and mabye even a hydro boost swap as its a lot better than vac brakes. but you will need hydro boost / brake pedel from same / lines / p/s pump from same.

hope this helps you pin point your problem.

p..s your bleaders are pointing up in the rear correct ? had a member here few years back do disk swap in rear couldnt get pedel and found calipers on wrong sides when at shop in 30 sec of mechanic looking it over.

 

[plyr2k]

should pump 1 time and be good thats first sign or not the right setup.

second yes by pass the rear abs and get rid of it not the best for our needs anyways. this gets rid of the 1 dist valve under the master with the wires going to it.

next the stock prop valve just tee's the front stright line pressure and volume. the rear part gets restricted a bit. and has the 1 tan or brown wire to dash bulb warning.

you can bypass the stock valve and do a tee in the front and stright to the rear threw adjustable vale and few test runs and dial it in. http://www.summitracing.com/parts/SUM-G3905/

or you can get aftermarket adjustable from summit http://www.summitracing.com/parts/WIL-260-11179/

also lots of guys find stock 1/2 ton master dosnt cut it for volume needed on MASIVE calipers of 1ton front and disk rear over TINY wheel cylinders in rear.

jump to a 1 ton master and mabye even a hydro boost swap as its a lot better than vac brakes. but you will need hydro boost / brake pedel from same / lines / p/s pump from same.

hope this helps you pin point your problem.

p..s your bleaders are pointing up in the rear correct ? had a member here few years back do disk swap in rear couldnt get pedel and found calipers on wrong sides when at shop in 30 sec of mechanic looking it over.

I'm going to look into bypassing my abs. Luckily all my stuff is right at the master. And yes, my bleeders are facing straight up. I've also read that a 3/4 ton master will push more fluid. But my 1/2 ton is brand new. So I plan on doing everything else seeing as it needs to be done anyways.
Thanks for the info.

 

[British Slave]

Are you using the original proportioning valve? If so, that's your problem. Go to Summit and get you an adjustable proportioning valve and thru trial and error set it like you like.


It's:

Wilwood brake proportioning valve, part # 260-8419 $41.95