Hydroboost and proportion valve question

[74BlueFish]

I tried to bleed my brakes and cant get fluid to the rear discs, and the front stay locked up.

I have a hydroboost from the astro van with the astro van master cylinder.  Do I need to remove the residual pressure valve from the mater cylinder,  I'm assuming it has one.   

Do I have to disable the proportion valve by removing the spring?

I'm pretty sure I have play at M/C pushrod when the pedal is not depressed.

I've never driven the car yet.  My set up is Astro van hydroboost and M/C, stock proportion valve, with adjustable proportion valve just downstream,  Dr Diff rear disc brakes, stock discs in front.
1974 Barracuda

If I have to take this all apart I want to get it right on this attempt.
Thanks

[Chryco Psycho]

I assume both the astro & your car have front disc & rear drum ?
 The front brakes should feed  from the closest port to the firewall off the master cylinder , the proportioning valve should be retained , I assume it was working before the swap to hydro boost ? The pushrod seems like the obvious problem as it will lock the front brakes if it is too long & it would prevent bleeding the rears if it cannot uncover the feed to the rear line inside the master so that is the first thing to check out .

[74BlueFish]

I think the astro had rear drums,  my car has rear disc now, was drums.   Yes   port closest to firewall is feeding front brakes.  Am trying to bleed front brakes as we speak and pushed pedal hard to try reset the proportion valve, but still no fluid to rear brakes.  I will try to shorten push rod right now.

[74BlueFish]

Push rod at hydroboost is short.  hydroboost fully retracted.  I never changed the length of the hydroboost to M/C push rod, i THINK IT WAS A FIXED LENGHT.   Damn Caps

I have never driven this car..  So I don't know if it ever worked.  Car now is 4 wheel disc but was rear drum.

[74BlueFish]

OK  another update,  master cylinder was bad,  won't pump fluid to rear brakes.    Should I replace it with a new astro van M/C   or buy a new different one.  Saw Wilwood sells one but is $215.  Don't want to spend that if the stock astro will work.    Also need to figure for sure if I should remove the spring in the proportion valve because I now have rear disc?

[brads70]

   subscribed.... I might be heading down this route soon. Just learning .

[74BlueFish]

Evidently, I'm still learning too?   

[73restomod]

Did you try to reset the pin on the prop valve? Some have a manual reset. Can't remember if you have to push or pull it.

[Cudakiller70]

OK  another update,  master cylinder was bad,  won't pump fluid to rear brakes.    Should I replace it with a new astro van M/C   or buy a new different one.  Saw Wilwood sells one but is $215.  Don't want to spend that if the stock astro will work.    Also need to figure for sure if I should remove the spring in the proportion valve because I now have rear disc?

I had a similar question on the proportioning valve, here's the thread.
http://www.cuda-challenger.com/cc/index.php?topic=108410.msg1065783#msg1065783
Maybe this would be help, there is a step by step instructions on how to rebuild your combo brake valve. Rebuild kit is $15. I got my kit in about 4 days. Took mine apart and it was filthy inside, very dirty.
https://www.musclecarresearch.com/1970-76-mopar-combo-valve-rebuild
https://www.musclecarresearch.com/1970-76-mopar-combo-valve-autopsy
https://www.musclecarresearch.com/1970-76-mopar-combo-valve-autopsy

My combo valve was missing a part for the brake light warning switch so I ended up getting the one without the built in proportioning valve all thanks to fellow CC er shawge
http://www.inlinetube.com/?_escaped_fragment_=product/prd14/2361736111/1970-72-e-body-distribution-block#!product/prd14/2361736111/1970-72-e-body-distribution-block
Because I too had a inline adjustable proportioning valve and didn't need it in the combo valve. Hope this makes sense?

[74BlueFish]

Thanks Resto,  Yes I tried to reset it.  Turns out I had only tried clean it from the out side I never took it apart.
I did so yesterday and it was stuck and real dirty.

Cudakiller,  yes I saw those threads, that why I was asking if I had to remove the spring in the valve.

My valve is different than the one in those threads where they remove the spring

This is my valve, can I remove this spring to get rid of the proportion valve feature on the valve.  See red box, will remove all but the cap.


The seal at the bottom of my valve is bad but won't use it any way  all other seal look good so just may reassemble the rest.

Thanks for all help.     

[Cudakiller70]

Thanks Resto,  Yes I tried to reset it.  Turns out I had only tried clean it from the out side I never took it apart.
I did so yesterday and it was stuck and real dirty.

Cudakiller,  yes I saw those threads, that why I was asking if I had to remove the spring in the valve.

My valve is different than the one in those threads where they remove the spring

This is my valve, can I remove this spring to get rid of the proportion valve feature on the valve.  See red box, will remove all but the cap.


The seal at the bottom of my valve is bad but won't use it any way  all other seal look good so just may reassemble the rest.

Thanks for all help.   

I'm not family with that valve maybe others could chime in. Is there a cutaway/section view available for it?

Here was my thinking on mine hopefully it will help. On my combo valve the way it was constructed even though it's all one piece, the proportioning section is separate from the brake warning light section. My plan was to take out the spring and piston for proportioning only, then that section just becomes a distribution block section. Still leaving the brake warning light switch still intact and working. The proportioning valve section of the combo valve would then just be a distribution block because I too have an adjustable proportioning valve for the rear disc brakes.

One other thing to check, I was told since my master cylinder is a stock Mopar front discs/rear drum and I now have rear discs. Their is a residual valve that's in the drum side of the master cylinder that feeds the rear, for mine it needed to come out.

i am no brake expert just finding everything I can online and testing on my car. Dr Diff also does brakes, he is great to talk to and responds quickly, he would be worth a try.

[Cudakiller70]

Any luck bluefish?

[Chryco Psycho]

you willwant to add an adjustable prop valve to balance brake pressures if you remove that spring

[74BlueFish]

I have the adjustable valve installed.    Assembled the proportion valve without the spring.  Have to buy a new master cylinder, hope to get it today and install tonite and try to bled the brakes,   hopefully will know if it works this evening.

[Cudakiller70]

I have the adjustable valve installed.    Assembled the proportion valve without the spring.  Have to buy a new master cylinder, hope to get it today and install tonite and try to bled the brakes,   hopefully will know if it works this evening.

Did you leave the green rod/nut assembly in?
I tried to find a cutaway of your valve with no luck though.