Bleeding brakes

[Goinlow64]

I installed disc brakes on front and read and went to bleed the brakes and ran into a couple of issues. When I ran a vacuum on the rear passenger brake I could not get fluid to come out. I pumped the pedal a good 30 pumps and then still no luck.

I popped the top off and found fluid level had gone down in the front reservor, but not the rear. So, my question is...do I need to do something special to the prop valve to get fluid to the rear? My front flex lines are also leaking a tad, but I didn't feel like breaking that down tonight. I am hopeful it is just a loose connection, but feel free to let me know if you think it oculd be somethin else!

Thanks!

[luvbowties]

Originally Posted by Goinlow64

I installed disc brakes on front and read and went to bleed the brakes and ran into a couple of issues. When I ran a vacuum on the rear passenger brake I could not get fluid to come out. I pumped the pedal a good 30 pumps and then still no luck.

I popped the top off and found fluid level had gone down in the front reservor, but not the rear. So, my question is...do I need to do something special to the prop valve to get fluid to the rear? My front flex lines are also leaking a tad, but I didn't feel like breaking that down tonight. I am hopeful it is just a loose connection, but feel free to let me know if you think it oculd be somethin else!

Thanks!

No. But you need to keep both reservoirs full while attempting to bleed them--pumping the m-cyl dry is not good for the m-cylinder. Did you properly bench bleed the master cylinder FIRST? It must always be done. Which reservoir feeds your rears? You'll have to fix the leaks on your front flex lines or you will NEVER get them bled.

[tincan1966]

If the system is completely new, with new lines, etc, the initial bleeding will be a process.
First, fix your known leaks. As luvbowties said, bench bleed the MC if it was installed new. I would suggest slightly opening the rear bleeders and allowing to gravity bleed. It'll take some time to get all the air out of a new system. We normally used a pressure bleeder here, or reverse bleed. That is done by using an pump style small oiling can full of clean brake fluid, attach a small hose to the end and to the bleeder screw. Remove the MC cap, open bleeder screw and pump fluid into the caliper. this can force air back "uphill" to the MC. You will see bubbles in the MC. I just recently was shown this method and am amazed at how well it works. Once the air is out, if you still need too, you can bleed the system normally again.

Hope this helps

[jonzcustomshop]

I ran into this problem too, the proportioning valve is the issue, I don't remember 100% what I did, but I did run a testlight on the prop. valve, had to open bleeders and pump until it centered, and the light went out, and then bleed like normal.... I think that was how it went.... I remember doing a bit of googling and reading to figure it out too, I think capt. fab might have helped me as well

[McCoyAZ]

Take it to Brake Mastes

best 50 bucks you will ever spend.

[rbar]

Just did mine with new lines from the master cylinder to the cross member for the back. I used a vacuum hand pump/pistol and it helped alot but still took way more time than I thought it should. Without the vacuum, I don't how long it would have taken.

[Captainfab]

It sounds like the proportiong valve is doing it's job. Likely what happened, is when you started the bleeding process, you had, no brake fluid at all in the front system, or the rear system. The proportioning valve saw this as a leak, and the valve slid over to block off the system that was 'leaking'. Is the front reservior on your master for the front or rear brakes? Which proportioning valve are you using? Basically what you need to do, is get the valve in the prop valve centered again, and get some fluid in that system by gravity bleeding first. Then go about your procedure of pressure or vacuum bleeding.