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rear disk caliper hang up

Don selleck

Don selleck

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installed wilwood 4 wheel disk brakes, ended up using an aftermarket stock appearing distribution valve with brake light plug on from classic industries and an adjustable rear proportioning valve from wilwood after that. when you hit the brakes all work good but the pressure on the rear stays when you let off the brakes? thinking i need to ditch the stock block or is there a way to remove the guts to the rear? assume there is a valve in there that is keeping the pressure applied, wondered if anyone has run into this, Thanks!
 
Sounds like the distribution block has a residual pressure valve built in... Post a picture of the valve..
 
The residual pressure valve is usually located in the master cylinder and could be removed if that is the problem.
 
this is the distribution valve
20190905_172530.jpg


MD2267_thumb.jpg
MD2267_thumb.jpg


+ Click to Expand

MD2267 - 1967-75 Mopar A/B-Body Distribution Valve
 
steve340 said:
The residual pressure valve is usually located in the master cylinder and could be removed if that is the problem.
Click to expand...
never knew about that, i assumed they all released when the brake pedal retracts.
 
that valve is the identical one that was in the car
 
Not that this addresses your problem but why did you add another prop valve to the system? The factory style ( if it's made for a disc/disc) should adjust the bias automatically.
Residual valves as I understand it are only needed if the MC is below the caliper to prevent drain back.
Now, are your brakes plumbed into the DB correctly?
 
Mike67 said:
Not that this addresses your problem but why did you add another prop valve to the system? The factory style ( if it's made for a disc/disc) should adjust the bias automatically.
Residual valves as I understand it are only needed if the MC is below the caliper to prevent drain back.
Now, are your brakes plumbed into the DB correctly?
Click to expand...

Residual valves are always used on drum brake systems... And Steve 340 is correct... My brain wasn't functioning this morning...

To verify the problem is residual pressure crack the line at the M/C & if the brake releases you know the problem is in the master....

Typically you can remove the brass seat insert by screwing a drywall screw in & using wire cutters to pop the seat... Behind that will be a rubber valve & a spring... Remove those & reinstall the brass seat...
 
Mike67 said:
Not that this addresses your problem but why did you add another prop valve to the system? The factory style ( if it's made for a disc/disc) should adjust the bias automatically.
Residual valves as I understand it are only needed if the MC is below the caliper to prevent drain back.
Now, are your brakes plumbed into the DB correctly?
Click to expand...
there are different sizes of lines that go into the block followed old configuration. pretty sure they are correct.
it states that the proportioning valve is for drum drum brakes and an additional valve is required for disk drum. I was gonna go with a 71 front disk set-up but with the clips and old engineering on a 600 hp car, i decided to upgrade, when I talked to willwood at the time i explained to the tech what i had and he stated i need the adjustable proportional for the back, and would work with the stock one that i purchased. So thats why i was thinking i might have a bad valve possibly, and with the mess this is gonna cause upon removal i was hoping someone might have remove something inside that might solve my problem
 
1 Wild R/T said:
Residual valves are always used on drum brake systems... And Steve 340 is correct... My brain wasn't functioning this morning...

To verify the problem is residual pressure crack the line at the M/C & if the brake releases you know the problem is in the master....

Typically you can remove the brass seat insert by screwing a drywall screw in & using wire cutters to pop the seat... Behind that will be a rubber valve & a spring... Remove those & reinstall the brass seat...
Click to expand...

So the question would be Is the MC a disc/drum, drum /drum or aftermarket???
Do after markets MCs have the residual valves built in also???
 
MD850300_thumb.jpg
MD850300_thumb.jpg
disk drum master
MD850300_thumb.jpg
MD850300_thumb.jpg

+ Click to Expand

MD850300 - 1966-70 Mopar B-Body With Disc/Drum Brakes - Power Brake Booster
 
1 Wild R/T said:
Residual valves are always used on drum brake systems... And Steve 340 is correct... My brain wasn't functioning this morning...

To verify the problem is residual pressure crack the line at the M/C & if the brake releases you know the problem is in the master....

Typically you can remove the brass seat insert by screwing a drywall screw in & using wire cutters to pop the seat... Behind that will be a rubber valve & a spring... Remove those & reinstall the brass seat...
Click to expand...
will check the brake line pressure at the master. i assume the seat you are referring to is inside the prop. valve?
 
You may be better to go to a disc/disc master cylinder as they displace different amounts of fluid compared to a disc/drum one.
It will also have no residual line pressure valves as they are not required with disc brakes.
 
i was hoping to preserve the original look under the hood as much as possible, the wilwood master was a thought but don't like the looks for my car, plus i have a chit load invested in this. but i definately see your point, thank you.
 
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