Good technique to re-center proportioning valve?

[RedRider]

Problem: no brake fluid going to rear after installing a new CPP disc conversion kit. Front lines are fine.

Here is what CPP suggests:



The dash brake light is on so I assume the differential valve is stuck, shutting off flow to the rear lines. I closed the rear bleeders and opened a front bleeder while gently depressing the brakes...no luck with the CPP approach. Maybe I'm reading it wrong though.

Any suggestions on recentering the valve? I've read online of people using a small wire (or similar) to manually move the valve back to center.

[mongocanfly]

a small screwdriver will recenter it.....they also make a special little tool you can run in there to hold it centered while you bleed

[mongocanfly]

here's the tool...https://www.speedwaymotors.com/Speed...RoCY-sQAvD_BwE

[RedRider]

Originally Posted by mongocanfly

a small screwdriver will recenter it.....they also make a special little tool you can run in there to hold it centered while you bleed

Thanks Mongo, I'll try this out. From the looks of it, I'm going to need a VERY tiny screwdriver. My prop valve is mounted horizontally so I can probably take a good picture of what you're talking about (for reference).

[RedRider]

I tried to move the valve manually with a small jewelers screwdriver, but no luck. It got scratched up (it's brass of course), so before proceeding further I wanted to try and wrap my head around what I'm trying to accomplish...so bear with me.

As mentioned, the valve is mounted sideways, so taking pictures is fairly easy:



With the brake wire removed:



Looking straight into the brake light switch hole, it appears the valve is moved to the right (towards the firewall) and needs to be moved to the left (toward the grille) to be re-centered? I assume the brake light wire fits in the middle of the groove on the valve? My apologies in advance for the kindergarten-level illustrations.

[Willie Makeit]

I bled the fronts first. Then the rears. Then the fronts again and the prop valve reset itself without any help from me.

[mongocanfly]

I can't tell from the pic which way it needs to move...but which ever way it needs to go you could try loosening a bleeder on that side and pump the brake...it "should" move by itself....

[sweetk30]

remove the rubber cap on the end of the valve .

there is a pin under there and needs to be held in place to hold the valve open .

the port under the switch only works when the valve is pushed in from the end .

[RedRider]

Originally Posted by sweetk30

remove the rubber cap on the end of the valve .

there is a pin under there and needs to be held in place to hold the valve open .

the port under the switch only works when the valve is pushed in from the end .

So I need to hold that pen open AND THEN try to move the valve over with a small screwdriver?

[sweetk30]

Originally Posted by RedRider

So I need to hold that pen open AND THEN try to move the valve over with a small screwdriver?

sorry for delay .

holding the pin in with the tool or other means keeps you from having to play with the switch at all.

[Keystone_Hate]

Try getting a buddy to help you. Do the CPP approach but instead of gently pressing the pedal, give it some good pumps and good hard hold on the last pump, then crack your front bleeders loose. If you think about it, in the operation of this thing in everyday circumstances, there will never be a slow, even, low pressure application of fluid to the valve that's gonna make it go over center. It's gonna be high pressure from your MC. Therefore give it some high pressure to nudge it back to where it belongs.

[RedRider]

Originally Posted by Keystone_Hate

Try getting a buddy to help you. Do the CPP approach but instead of gently pressing the pedal, give it some good pumps and good hard hold on the last pump, then crack your front bleeders loose. If you think about it, in the operation of this thing in everyday circumstances, there will never be a slow, even, low pressure application of fluid to the valve that's gonna make it go over center. It's gonna be high pressure from your MC. Therefore give it some high pressure to nudge it back to where it belongs.

Makes sense. It's worth a try at this point, thanks!

[RedRider]

Grrr!!! This weekend I wasted a whole bottle of brake fluid trying to get this $#%& combination valve to re-center. I finally gave up and ordered another one on Ebay. For $40 it comes with the tool Mongo mentioned above.

It's sold by a pirate so it has to be good right?
https://www.ebay.com/itm/161058469851

[mongocanfly]

haha....pirate jack.....what could possibly go wrong?.....haha

[Willie Makeit]

Originally Posted by mongocanfly

haha....pirate jack.....what could possibly go wrong?.....haha

have bought several brake components from them over the years. you will NOT find better customer support than these folks.

[RedRider]

Originally Posted by Willie Makeit

have bought several brake components from them over the years. you will NOT find better customer support than these folks.

Thanks Willie, good to hear. Although anything is better than the customer support at CPP.

[Willie Makeit]

go to your local pharmacy and ask for a 2 oz syringe and about 2 feet of surgical tubing. draw fresh brake fluid into syringe, place the tubing over the bleed valve and force fluid BACKWARDS thru the system (from wheel cylinder to master cylinder). once you've done this with all 4 wheels, try to bleed again. lasts time i bought these two items it was less than $2.

p.s. remember to remove some fluid from MC before reverse bleeding. if not, you're gonna make a mess on the MC end

[RedRider]

Update: received a new combination valve from Pirate Jack (you we’re right about the great service Willie). When I installed it the brake light went off, which I assume means that it’s centered. At that point I screwed in the special tool to hold it in place.
I tested it by disconnecting the rear line from the combination valve to see if fluid came out when pumped....nothing. Am I missing something? Or is it still not centered?

[mongocanfly]

have you checked your master to see if its pumping fluid? while you had the lines loose for the valve swap , fluid should have run out of the lines more than likely draining the reservoir...would have been a good time to rebleed the master

[RedRider]

Originally Posted by mongocanfly

have you checked your master to see if its pumping fluid? while you had the lines loose for the valve swap , fluid should have run out of the lines more than likely draining the reservoir...would have been a good time to rebleed the master

Good point, I may be getting ahead of myself. I'll start with a bench bleed again and go from there.

[Willie Makeit]

before removing the MC from the truck completely, remove the outgoing brake lines and plug the outgoing ports then see if you have a firm pedal. if so, then your MC is fine. if not, try the bench bleeding procedure again.

once you have established your MC is good, then bleed the FRONTS first, then the rears, then the FRONTS again. the prop valve needs to see pressure on the fronts before it will allow the rear circuit to open.

[RedRider]

Originally Posted by Willie Makeit

before removing the MC from the truck completely, remove the outgoing brake lines and plug the outgoing ports then see if you have a firm pedal. if so, then your MC is fine. if not, try the bench bleeding procedure again.

Thanks Willie, I did like you said and the pedal is firm. HERE’S a problem though; with all the lines off the MC, I’m getting NO fluid out the rear port. When I push the brakes I get plenty gushing out the front though. This is a brand new master cylinder too!

[mongocanfly]

sounds like you just found your problem....

[RedRider]

The saga continues...

Installed a new master cylinder and finally got fluid going back to the rear...almost. The rear rubber brake hose was clogged (why I didn't replace it along with the rest of the brake system I don't know), so I installed a new one. Now I finally got fluid to all four corners. Next is brake bleeding, and hopefully not another can of worms to open.

[mongocanfly]

sounds like my kind of "saga".....