Brakes locking down

Suspension, Brakes, Tires, Wheels etc..

Brakes locking down

Postby spoilerecw » Wed Oct 18, 2017 6:25 am

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
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Re: Brakes locking down

Postby PwrWgnDrvr » Wed Oct 18, 2017 10:01 am

Do u have any old, original, rubber flex lines in the front?
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Re: Brakes locking down

Postby spoilerecw » Wed Oct 18, 2017 3:45 pm

No their new braided steel lines to the calipers in front and the rubber line at rear brakes is a new one. Thanks.

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Re: Brakes locking down

Postby Jim100 » Wed Oct 18, 2017 6:10 pm

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?
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Re: Brakes locking down

Postby Txas2step » Thu Oct 19, 2017 5:38 am

You need a dual disc/drum master and I used a disc/drum dist. block I purchased on Ebay. :Thumbsup
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Re: Brakes locking down

Postby soopernaut » Thu Oct 19, 2017 11:10 am

I don't think front disc/rear drum is going to work with a single reservoir master cylinder.
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Re: Brakes locking down

Postby dodgeboykim » Thu Oct 19, 2017 1:49 pm

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
My truck is younger than me.
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Re: Brakes locking down

Postby BigJimG » Fri Oct 20, 2017 8:16 am

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.
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Re: Brakes locking down

Postby spoilerecw » Fri Oct 20, 2017 7:03 pm

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.

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Re: Brakes locking down

Postby PwrWgnDrvr » Fri Oct 20, 2017 10:14 pm

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.
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Re: Brakes locking down

Postby spoilerecw » Sat Oct 21, 2017 6:19 am

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.

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Re: Brakes locking down

Postby Jims68 » Sat Oct 21, 2017 6:47 am

PwrWgnDrvr wrote:There is an RPV in the stock master.


Just curious... what is an RPV?
Jim

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Re: Brakes locking down

Postby BigJimG » Sat Oct 21, 2017 7:12 am

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.
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Re: Brakes locking down

Postby Jims68 » Sat Oct 21, 2017 8:14 am

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:
Jim

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Re: Brakes locking down

Postby soopernaut » Sun Oct 22, 2017 6:48 am

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Re: Brakes locking down

Postby spoilerecw » Sun Oct 22, 2017 1:26 pm

Great Info soopernaut, thanks a lot!!!!!!!!!

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Re: Brakes locking down

Postby Kaegi » Mon Nov 06, 2017 1:16 pm

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.
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