Brake issues

[cldonley]

I have Explorer rear disc, Chevy front disc on a 69 with hydro boost. Haven't appllied the brakes with the engine running yet, so haven't tested the hydroboost at all. I have a brand new WH heavy duty master cylinder advertised as specially set up for hydroboost, bench bled using the plug method. I have the WH Moab adjustable prop valve. I have new calipers on all four corners with new pads and new lines from front to back. Using the H block with WH flex lines running from the prop valve to the H block. I cannont find a leak anywhere, but when I bleed the brakes with a friend's help, the brake will feel firm, then a minute later if I apply the brake I have to pump it up again. What am I missing? The reason I have a new WH MC is because I was spitballing the problem and replaced an older WH MC. I was thinkning about removing the prop valve to see if it made any difference. I have only a few things left to make the rig road worthy and these brakes are driving me nuts!

 

[gnpenning]

Disconnect the brake lines and and bleed. Let it sit for awhile or a day and see what happens. Next would be doing the same thing at the prop valve.

You need to be isolating items and narrowing it down. Verify one section before moving on to the next.

 

[ba123]

I wouldn’t disconnect unless you’ve tried everything else and can’t find it.

Pound on the brakes, hold the brakes, keep doing it…

After a bit, feel the underside of every single connection.

You will find a wet one.

If you keep doing this and still can’t find it, then yes, disconnect and try cause it might be the master but I think that’s a last resort.

 

[stupidboy]

I’m not a fan of the plug method on the bench bleeding, I would try the other method first.

 

[cldonley]

I’m not a fan of the plug method on the bench bleeding, I would try the other method first.

It was my first time trying it. Seemed to work pretty well. I will go back and try that if I can't get it sorted.

 

[Wild horse 75]

If you got the master to the point you couldn’t push the piston in anymore it’s bled. Do you have the e-brake hooked up yet? What you’re describing seems to me like the rear pistons haven’t been screwed out far enough yet and you’re taking up the space by pumping the pedal.

 

[cldonley]

If you got the master to the point you couldn’t push the piston in anymore it’s bled. Do you have the e-brake hooked up yet? What you’re describing seems to me like the rear pistons haven’t been screwed out far enough yet and you’re taking up the space by pumping the pedal.

It's explorer rear disc so the e-brake doesn't impact the caliper operation. The calipers at all four corneres are against the disc like they should be.