47-59 brake pressure

[not2oldchevy]

3 master cylinders 2prop valves no pressure on rear brakes front c4 corvette rear 8.8 explorer all new lines and hoses 4 wheel disc

[geezer#99]

What’s the m/c bore size and the pedal ratio?

[leegreen]

how did you bleed it?

[Rickysnickers]

What kind of proportioning valves? Were they the ones that needed to the small tool to press the button down to bleed correctly?

[dsraven]

can you explain what your set up is? pics would also be great.
what master cyl and how are the lines connected for front and rear lines? is the master built for a disc/disc set up? (pic)
is there a little pedal freeplay when released and also freeplay at the pushrod for the master cyl so that the master cyl can return fully when brakes are released? does your pedal have a stopper or bumper at the fully released position and also a return spring capable of moving the entire mechanism back against the stopper/bumper when released?
what is your pedal travel before you feel brake resistance and does the pedal get hard at the end of the travel before it hits the floor? spongy at all?
have you tried to see what pressure there is at the ports of the master cyl for the rear line or possibly at the rear brake inlet port of the prop valve?
if running a booster have you checked for the correct clearance between the booster pushrod and the master cyl piston? to ensure the master cylinder is able to return fully, but also to ensure it can get a full stroke to the end of it's bore
are you familiar with the prop valve in your system and how it works? bleeding the brakes can set the prop valve internal mechanism off center and this can cause one circuit to not receive pressure. it is a safety mechanism. in the case one circuit failure, due to fluid or pressure loss for some reason, the internal piaton of the prop valve shuttles over to close that circuit off and that allows the other circuit to operate to avoid a complete system failure due to loss of fluid in the system from a leak. anyway, the prop valve may have shuttled during bleeding and may simply need to be reset. rickysnickers input

[dsraven]

speedway motors has a pretty good explanation of how a prop valve works, how to connect the ports and how to reset one. for some reason I am not able to paste the link here today but if you google "how to reset a brake proportioning valve" the speedway write up will come up. it shows a cutaway of the valve and gives port connections etc

[dsraven]

https://www.speedwaymotors.com/the-t...ustment/134183

[dsraven]

got it. dunno why the paste option wouldn't show previously.
anyway, maybe help somebody lurking if nothing else.
here is one on brake booster pushrod adjustment. again, maybe you have done this but a lurker may benefit
https://youtu.be/WI_CXBJ6J3E?si=6w15QUfRgds86JAb

[dsraven]

prop valve (combination valve) video. how it works, how to connect, how to bleed, how to reset
https://youtu.be/qPLaPv8DITE?si=vjxK0vZl5YNopgVM

[mr48chev]

The link worked. That proportioning valve bleeder tool that they show way down the page would saved me a lot of time and some real headaches over the years if I had had one or a set. You can actually push that piston to one side so hard and far while bleeding brakes that it breaks the tip that sticks out and jams things up something terrible and then you have to find a new switch.

[dsraven]

ok, good. dunno why it didnt post the first time around.

[geezer#99]

Originally Posted by dsraven

ok, good. dunno why it didnt post the first time around.

Could ya find a better link!
Every time I watch an Uncle Tony vid I nod off in the first few minutes.

[dsraven]

haha, well it was just the first link that I found by a quick google search. I suppose the original poster could look a little deeper for a better one if that seems to be the problem to worry about.
do you have a better link in mind that you wanna share?