confusion over distrobution/proportioning block

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Duster_71

Duster_71

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Hello All,

I’ve been wrestling with a brake problem since I’ve switched to disc up front, 74 Duster originally drums all the way around. Installed factory disc up front and then installed Dr. Diff 10” drums in the back, new brake lines, SBP to LBP all the way around. Installed Dr. Diff aluminum master with 15/16 bore and a distribution block from inline tube (1969-1974 Mopar A-Body Disc or Drum Brakes Distribution Block).

My question revolves around the distribution block, Inline tube calls it a distribution block but Dr. Diff site calls a similar item a proportioning valve (Mopar 1 Piece Proportioning Valve). I can’t figure out if these are one in the same or if the inline tube one is actually a distribution block and Dr, Diff’s is a proportioning valve.

I’m wrestling with this because my brakes don’t seem to want to stay bled. Master was bench bled and the whole system bled just fine. When I bleed the brakes I have great brakes for several weeks but then they start to get mushy and I have to eventually bleed them again, rinse repeat. I see no apparent fluid leeks at any of the junction points and when I bleed the brakes the air seems to only be upfront. I’ve replaced the master several times and now I’m starting to wonder if it comes down to the distribution/proportioning valve. Additionally, I started to read about and wonder about any residual pressure valves. Any and all constructive information/criticism welcome.
 
1- bleeding: you are getting air in somewhere. is there a wet spot?

2- proportioning: I am 99% convinced Moapr accomplished "proportioning" by varying the bore sizes in the wheel cylinders and/or caliper pistons. I doubt there is any actual proportioning done in the valve/distribution block.
 
YY1 said:
2- proportioning: I am 99% convinced Moapr accomplished "proportioning" by varying the bore sizes in the wheel cylinders and/or caliper pistons. I doubt there is any actual proportioning done in the valve/distribution block.
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That's not what is meant by a proportioning valve.
Even though it is true that the amount of force and distance traveled by choosing different size wheel cylinders.
Proportioning valves only come into play above a set pressure.
Read here: 1967 Chrysler Imperial Disc Brake System From the Master Technicians Service Conference Session 233

And then go here for the combined units:
1970 Chrysler Imperial Hydraulic Brake Service Guide from the Master Technicians Service Conference Session 274

Note that Chrysler generally called the distribution blocks the safety switch starting in '67 (dual master cylinder systems).
 
A distribution block per se is NOT the same as a prop valve that happens to be incorporated such that it also "distributes" the tubing. The clue PHYSICALLY (I'm not talking about a "stock" photo---) is that a DRUM distro block is always symmetrical, and the prop valves are always very much lopsided looking like the photo you referenced.

Some installations used a separate metering valve.........one line in and one line out

Below is a drum system distro block. Notice the symmetrical appearance compared to the prop valve

db_20060723_pics_0071-jpg.jpg


Some help might be if you go over to MyMopar and download the 70--72--73 service manuals and look through them. I have found some reference online that some cars also used a prop valve PLUS a metering valve. I cannot confirm that as factory as I simply don't have info on that
 
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Confused? How about this setup for some B bodies around 69? 70

untitled-jpg.jpg
 
Duster_71 said:
I’m wrestling with this because my brakes don’t seem to want to stay bled. .
Click to expand...

Actually the whether/ or not/ type of metering/ distro/ prop valve has NOTHING to do with brakes "staying bled."
 
67Dart273 said:
Actually the whether/ or not/ type of metering/ distro/ prop valve has NOTHING to do with brakes "staying bled."
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Understood, didn't know if it had anything to do with the rear cylinders and pressures or just something that could impact it.
 
67Dart273 said:
Some help might be if you go over to MyMopar and download the 70--72--73 service manuals and look through them. I have found some reference online that some cars also used a prop valve PLUS a metering valve. I cannot confirm that as factory as I simply don't have info on that
Click to expand...
Yes. But what is meant by metering valve is not a proportioning valve. It's to hold off the front brakes at the very lowest pressure to reduce front lock up on ice. Never used on A-bodies AFAIK.
List of which cars got which
1970 Chrysler Hydraulic Brake Service Guide p.9

Explanation, bottom right of page.
1970 Chrysler Hydraulic Brake Service Guide p.11
 
Check for leaks inside the car at the master cyl. The rear ports / piston on the MC is for the front brakes. My MC leaked there and went between carpet and body. You would have never known.

When you re-bleed the brakes are you getting air bubbles out?

Have you tried gravity bleading the front discs?
I had a car that took weeks to get the trapped air out from a MC replacement, o must have bleed a pint of fluid thru it.
 
Duster_71 said:
Hello All,

I’ve been wrestling with a brake problem since I’ve switched to disc up front, 74 Duster originally drums all the way around. Installed factory disc up front and then installed Dr. Diff 10” drums in the back, new brake lines, SBP to LBP all the way around. Installed Dr. Diff aluminum master with 15/16 bore and a distribution block from inline tube (1969-1974 Mopar A-Body Disc or Drum Brakes Distribution Block).

My question revolves around the distribution block, Inline tube calls it a distribution block but Dr. Diff site calls a similar item a proportioning valve (Mopar 1 Piece Proportioning Valve). I can’t figure out if these are one in the same or if the inline tube one is actually a distribution block and Dr, Diff’s is a proportioning valve.

I’m wrestling with this because my brakes don’t seem to want to stay bled. Master was bench bled and the whole system bled just fine. When I bleed the brakes I have great brakes for several weeks but then they start to get mushy and I have to eventually bleed them again, rinse repeat. I see no apparent fluid leeks at any of the junction points and when I bleed the brakes the air seems to only be upfront. I’ve replaced the master several times and now I’m starting to wonder if it comes down to the distribution/proportioning valve. Additionally, I started to read about and wonder about any residual pressure valves. Any and all constructive information/criticism welcome.
Click to expand...
I had this with a Durango once. turned out a bad rear wheel cyl cup was allowing air in, sometimes but never leaked. inside the rear drums was dry and dusty, no sign of fluid.
Replaced both rear wheel cylinders and it never happened again!!
 
motorpirate said:
I had this with a Durango once. turned out a bad rear wheel cyl cup was allowing air in, sometimes but never leaked. inside the rear drums was dry and dusty, no sign of fluid.
Replaced both rear wheel cylinders and it never happened again!!
Click to expand...

How did you figure out that it out?
 
You might check if the master has a residual pressure valve for the rear brakes and make certain you actually have the rear brakes connected to that section. Normally, the rear brakes go to the front connection. A residual valve helps prevent the above problem--it helps keep a small positive pressure in the circuit
 
Pirate jacks sold me this setup and said i had to have both and the master had to be changed too. Has a small resivoir up front. I had quite a few leaks everywhere that were minor but caused the same issue. Very hard to notice them. I also had to add another porportion valve in there for the front like the e bodies

View attachment 1715468704

20190417_195821.jpg
 
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Air up front you mentioned. leaking calipers. But i cant see how. The seals are pretty tight in them. Especially if they are new.
Air would have to be pulled in through the dust boots as well.
residual valves are 2-3 psi on disc brakes and as much as 10 psi on drums.
disconnect battery and block pedal down,leave it there. The leak should show up.

One tell-tale, how many pedal cycles does it take to get air out?
For example if air is right away, its in caliper, if its several pumps then its master or combi valve.
 
67Dart273 said:
Confused? How about this setup for some B bodies around 69? 70

View attachment 1715468389
Click to expand...

Older pre 71 A body with KH Used as well. My 69 does.

Pic posted in the link of the first post is correct 71 up. The “Texas valve was added to the distribution valve. Not the best setup if using aftermarket components. Loosing bleed is another issue entirely. Could be leakage or could be a poor master.
 
1969383S said:
Older pre 71 A body with KH Used as well. My 69 does.

Pic posted in the link of the first post is correct 71 up. The “Texas valve was added to the distribution valve. Not the best setup if using aftermarket components. Loosing bleed is another issue entirely. Could be leakage or could be a poor master.
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That B-body illustration shows both a proportioning valve and a metering valve. The latter was never used on factory a-bodies.
Duster_71 said:
My question revolves around the distribution block, Inline tube calls it a distribution block but Dr. Diff site calls a similar item a proportioning valve (Mopar 1 Piece Proportioning Valve). I can’t figure out if these are one in the same or if the inline tube one is actually a distribution block and Dr, Diff’s is a proportioning valve.
Click to expand...
Do you understand now? They are both combination valves. They appear to be the same. The application information is not quite correct with respect to dates of use. Don't believe me 'cause I typed it here. Go read what Chrysler printed in 1970.

MerlinsMopar said:
Pirate jacks sold me this setup and said i had to have both and the master had to be changed too. Has a small resivoir up front. I had quite a few leaks everywhere that were minor but caused the same issue. Very hard to notice them. I also had to add another porportion valve in there for the front like the e bodies
Click to expand...
Please go read Chrysler's introduction to Dual Hydraulic Brake systems.
1967 Imperial & Chrysler Dual Hydraulic Brake Repair Book - Session 232
and then at least this section about the proportioning valve
http://www.imperialclub.com/Repair/Lit/Master/233/page06.htm
 
You say it is a new master cylinder. Just because it is new, that doesn't mean it can't be defective. I had that happen once. I pulled out my hair for weeks. I looked carefully for leeks/wetness, and could not find any. I finally got another new master cylinder; problem solved. I always tell everyone; never assume that a new part cannot be defective.
 
Thanks everyone, I have discovered another symptom that someone may be able to shed some light on. Car is currently up on jack stands and when I turn the steering wheel the entire way side to side it pushes brake fluid up through the master cylinder an forces fluid out around the caps.
 
Calipers on upside down, pinching a brake line? Like smashing it? I cant even see that much fluid displacing from a smashed line. Steering should have zero effect on hydraulic pressure.
 
pishta said:
Calipers on upside down, pinching a brake line? Like smashing it? I cant even see that much fluid displacing from a smashed line. Steering should have zero effect on hydraulic pressure.
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This hole thing is kicking my ***. Calipers are correct(bleeders on top) and lines do not get pinched.
 
harrisonm said:
You say it is a new master cylinder. Just because it is new, that doesn't mean it can't be defective. I had that happen once. I pulled out my hair for weeks. I looked carefully for leeks/wetness, and could not find any. I finally got another new master cylinder; problem solved. I always tell everyone; never assume that a new part cannot be defective.
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I get it, master cylinder has been replaced twice with new units. I can't believe I could be unlucky 3 times in a row.
 
Hoses short and pulling on calipers? Thats something un related to the air in system.
 
Tooljunkie said:
Hoses short and pulling on calipers? Thats something un related to the air in system.
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Visually, they do not appear to short when the wheels are turned the hole way. They do not seem to be stretched and have enough excess.
 
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