Like Tancuda in his post, I cannot bleed the rears. Fronts bleed fine. The master cylinder is new and is bench bled. With rear brake lines removed from the cylinders, I get nothing. I bought a pressure kit from Motive (just the pressure fixture in place of the master lid) and even with 20lbs of air pressure into the master, still nothing to the rear lines.

So, I have a coupla possibilities:
1. Combo valve issue.
2. Rusted shut in the main line.

If it's the combo valve, is it because the switch plunger is stuck in the way?
I doubt the line rusted shut so well that I can't force at least SOME fluid through it with pressure.

I'm thinking combo valve issues.

 

How about the rubber hose between the body and the rear differential?

 

Some things were replaced by my buddy before and the rubber line looks darn good.
I can pull it loose though and verify that there is or isn't fluid to at least there.

 

Do you know if the bleeder screws are clear? Have you removed the screws completely? Have you verified that the outlet ports in the wheel cylinders are clear of rust flakes?

 

I pulled the lines loose from the wheel cylinders to remove that as a possibility. I said that in my original post, but I get wordy so you may have missed it

 

Eric mentioned the rear hose. That would be one of the first things I check.

 

Did you pull the line loose at the input to the combo valve? At the output from the combo valve? At the input to the rubber line at the frame crossmember? This is just like troubleshooting electrical problem. Start where you know you have fluid and check each connection in sequence until you don't.

 

Yes, I plan on doing the troubleshooting sequence today. I have the lines soaking in Aerokroil as I don’t want the hard lines snapping off when I start opening them up. Plus, I have everything back together by the combo valve and I’ll start taking it all apart if/when I have to.

One question I need addressed that hasn’t been touched on.

Is there a plunger/piston inside the combo valve that *could* be stuck preventing flow to the rear? Is that a thing?

 

I forgot to ask if the brake light on the dash is lit with the parking brake disengaged and the key on?

 

Oh yeah. The brake light is not on with ignition on. I’ll go ground the wire to verify that it will come on.

 

As noted above, the piston that operates the BRAKE warning light will restrict flow of pushed all the way to one side.

 

There is no note above about the piston restricting flow if pushed to one side. Not in this thread anyway.

 

That's what Oldcutlass was getting at. If the piston is pushed to one side, the BRAKE light will be on.

 

That was not explicitly addressed. Hence, my direct question about the piston blocking.

Brake light is not on with ignition on, but grounding the wire makes the light come on.

So it seems that there is blockage somewhere from the master cylinder to the rear axle. The main hardline to the rear WILL NOT come loose from the rubber line. It’s about to round the head off even with a line wrench.

I’ll start with jacking the engine up (again), remove the header (again), and try to get the hardline to the rear loose from the combo valve and see if there’s fluid out of there.

I’ll report back in a little while.

 

Strong chances are that the rubber line is culprit of your issue.

 

Ok, before I go through all the trouble with getting everything out of the way to get to the combo block, I’ll work on getting things loose at the rubber line.

 

Got the hardline loose at the input to the rubber line (finally, with very tight Vise-grips without damaging the flare nut). Guess what? Fluid came out of the hardline. However, no fluid at the other end of the rubber line. Thanks all, it's great being able to bounce this stuff off of you all before attempting decisions. I'll see if any stores have the rubber line locally today so I can put the brake system to rest and move on to the exhaust. Exhaust will be the last big job before it's just detailed reassembly and fire up.

 

Oh, also, one more thing! The hold down bolt for the rubber line that goes on the top of the rear axle housing is missing. It is difficult to get my head up there, but if I know what the bolt/thread is supposed to be, I could find/buy something that will work.

What's the size/thread of it?

 

I just checked one of my spare rearends and a 5/16” coarse thread bolt fit that hole.

 

That is 5/16-18 don't know the length.

 

Oh, cool, I'll dig through my pile and find something suitable.
BTW, I put 100lbs. of air pressure into the rubber hose and it is completely plugged. Nothing goes through it. I think I'm gonna cut it open and see what it looks like...

Thanks a bunch all!

 

Basically the inside of the hose breaks down and collapses. It's pretty typical and happens to the front brake hoses as well.

 

I have had front hoses act like a check valve where fluid would go through them but then the wheel cylinder would not release. The first one I had do that on a 72 Cutlass me scratching my head and spewing out some words I could not put on here. I don't remember how I figured it out but I know I will never forget it.

 

Got the new hose. I'll put it on tonight, bleed, then the brakes will be done front to back!
Thanks all...