Page 1 of 1

Brakes locking down

Posted: Wed Oct 18, 2017 6:25 am
by spoilerecw
Been working on my 62 D100 and finished my Scotts IFS swap in front and have taken it for a couple drive and have noticed the front brakes which are now disc seem to not want to release fully and my brake pedal is very stiff with little travel. Have new rear drum brakes that are adjusted properly. Have the factory single reservoir master cylinder, non power. Do I need to replace the distribution block on the frame with a adjustable proportioning valve? Anybody run into this before?

Brandon in Oklahoma

Re: Brakes locking down

Posted: Wed Oct 18, 2017 10:01 am
by PwrWgnDrvr
Do u have any old, original, rubber flex lines in the front?

Re: Brakes locking down

Posted: Wed Oct 18, 2017 3:45 pm
by spoilerecw
No their new braided steel lines to the calipers in front and the rubber line at rear brakes is a new one. Thanks.

Brandon

Re: Brakes locking down

Posted: Wed Oct 18, 2017 6:10 pm
by Jim100
If going to disc brakes I thought I read here that one needs to use a disc brake master and also use an proportioning valve?
This was for a disc dana 44 swap but seems like it would be the same?
jim

Re: Brakes locking down

Posted: Thu Oct 19, 2017 5:38 am
by Txas2step
You need a dual disc/drum master and I used a disc/drum dist. block I purchased on Ebay. :Thumbsup

Re: Brakes locking down

Posted: Thu Oct 19, 2017 11:10 am
by soopernaut
I don't think front disc/rear drum is going to work with a single reservoir master cylinder.

Re: Brakes locking down

Posted: Thu Oct 19, 2017 1:49 pm
by dodgeboykim
soopernaut wrote:I don't think front disc/rear drum is going to work with a single reservoir master cylinder.

And you have no safety back up with a single master cylinder if something goes wrong. :thinking :thinking :thinking :thinking

Re: Brakes locking down

Posted: Fri Oct 20, 2017 8:16 am
by BigJimG
I don't remember for sure, but doesn't the stock master cylinder have a built in residual valve? That could cause some interesting issues with front discs.

Re: Brakes locking down

Posted: Fri Oct 20, 2017 7:03 pm
by spoilerecw
Ya I know that it would be better with a dual master cylinder reservoir, but I'm not the best about flaring brake lines, ha. Was wanting to just stick with the single reservoir if I could. Thanks.

Brandon

Re: Brakes locking down

Posted: Fri Oct 20, 2017 10:14 pm
by PwrWgnDrvr
There is an RPV in the stock master. That is your problem.
Why would you go to all this trouble to swap in disks and not do the job right and safe? (dual master)
Mess with the brakes, hurt someone in an accident, their atty will rip u apart and your insurance company will probably not cover it claiming u defectively modified it.

Re: Brakes locking down

Posted: Sat Oct 21, 2017 6:19 am
by spoilerecw
Ha didn't know I was going to get griped out, was just wanting some advice. Thanks for all the help, I went with the single reservoir cause it was new and didn't think of it causing an issue and the way Im going to drive the truck in rural western Oklahoma with not much traffic and a all new brake system didn't think I would have a issue of a leak that I would loose the fluid. Thanks, I'll get it changed.

Brandon

Re: Brakes locking down

Posted: Sat Oct 21, 2017 6:47 am
by Jims68
PwrWgnDrvr wrote:There is an RPV in the stock master.
Just curious... what is an RPV?

Re: Brakes locking down

Posted: Sat Oct 21, 2017 7:12 am
by BigJimG
Jims68 wrote:
PwrWgnDrvr wrote:There is an RPV in the stock master.
Just curious... what is an RPV?

Residual Pressure Valve. The aftermarket ones keep approx 2-10 psi remaining in the brake line to prevent the wheel cylinders from completely retracting, kind of like an infinitely adjustable brake adjuster... Not sure what value the stock one leaves in the system, but probably pretty close.

The only time I've ever seen them used with disc brakes, the 2 psi fixed valves were used when the master cylinder was mounted below the floor to prevent a backflow situation.

Re: Brakes locking down

Posted: Sat Oct 21, 2017 8:14 am
by Jims68
BigJimG wrote:
Jims68 wrote:
PwrWgnDrvr wrote:There is an RPV in the stock master.
Just curious... what is an RPV?

Residual Pressure Valve. The aftermarket ones keep approx 2-10 psi remaining in the brake line to prevent the wheel cylinders from completely retracting, kind of like an infinitely adjustable brake adjuster... Not sure what value the stock one leaves in the system, but probably pretty close.

The only time I've ever seen them used with disc brakes, the 2 psi fixed valves were used when the master cylinder was mounted below the floor to prevent a backflow situation.
Thanks! See? Ya learn something everyday! :lol:

Re: Brakes locking down

Posted: Sun Oct 22, 2017 6:48 am
by soopernaut

Re: Brakes locking down

Posted: Sun Oct 22, 2017 1:26 pm
by spoilerecw
Great Info soopernaut, thanks a lot!!!!!!!!!

Brandon

Re: Brakes locking down

Posted: Mon Nov 06, 2017 1:16 pm
by Kaegi
only way to keep the single reservoir is to take apart the master cylinder, remove the residual pressure valve, buy a remote mounted 10 psi residual valve and install it on the line that goes to the rear brakes. you dont need a residual valve for disk brakes unless you are running an older car with nan under the floor mater cylinder.