ok, I'm about to loose what little sanity I have left, I've reviewed many previous threads, and have ran out of things to check.
stock 86 t type, it has been converted to vaccuum master cylinder. I'll be very descriptive to try and speed learning curve.
I drove the car only once before pulling the rearend to get it overhauled, the brakes where working, but didn't feel like they where working as good as they should. I had pulled the rearend for other reasons, not because of the brakes. (thought I had better mention that or you guys might really think I was a ding dong
I reinstalled rearend and went to bleed the brakes, I started bleeding in sequence from the wheel closest to the master cylinder to the farthest, (which I now know is wrong, I shoud have done it opposite, but I didn't know that till now.) I could get the fronts to bleed with good solid pedal, but couldn't get the rears to bleed (was getting very very little fluid to come out of the bleeders, and pedal would hardly move). I have blead the brakes on many cars and have never had problems, so I figured my combination valve might not be working. I cracked the line on it going to the rear...nothing. the valve was the cast steel one and very corroded. I ordered a new brass ac delco one from postons and installed. Same results. I then cracked the lines right off the master cylinder. The line for front brakes was working great (as I already knew since front brakes felt great), but the rear line wasn't pushing anything. So I figured the master cylinder was plugged somehow, (the fluid was a little dirty in the resevoir, and the whole vaccuum master cylinder assembly looks like it probably came from a another gbody car, another words, not new.) So I ordered a brand new master cylinder and installed. I blead the cylinder per the instructions.... until all air was purged from the clear hoses that came with the kit (routes the fluid back into both resevoirs). I then hooked up lines and blead in the same sequence from wheel closest, to farthest away,... and still same results. So I started doing some reading, and learned I should be bleeding them opposite due to the way the combination valve works. I had thought maybe I need to depress the button on the valve while I bleed since it says I may need to do that in my 87 buick service manual, but according to some previous post here, lots of you have never messed with that valve and blead ok.
I also checked the rear pistons to make sure they where free and clear and not pinched or slanted.
My 87 buick service manual says that in a conventional brake system, (disc in front, drum in back) I should bleed from farthest away from master cyinder first. Since my front brakes where free of air and firm, I figured I should crack the lines and pump them and put some air in them so they won't build pressure, and the combination valve will instantly send fluid to the rear. So I did that, and started to bleed from the farthest wheel away first, and got very little fluid with the brake pedal not going down hardly at all when I blead, same as before. I should also note, that when I went to bleed the right rear after I had installed the master cylinder, (before I knew of the bleeding sequence) that I got lots of fluid, and pedal went all the way to the floor, but when I went to the left rear, I couldn't get it to bleed.
I then went back to the combination valve and cracked the line going to the rear (to make sure that my rear lines wheren't maybe restricted or clogged somewhere), but it wouldn't bleed either.
So now I don't know what the heck to do. I've changed everything in the freakin system.
I have kept the resevior full, at all times, its never went empty.
I have put the cap back on, after every time I would top it off after bleeding.
I've never started the car, according to previous post, you'll always get a better blead system if you don't.
I have been correctly bleeding it, with one person pushing and holding brake pedal while I tighten the bleeder at each wheel, so's not to let air back in the system.
thats about all I can think of. anybody have any ideas? This car will be used as a daily driver. I want all 4 corners to be working as they should.
stock 86 t type, it has been converted to vaccuum master cylinder. I'll be very descriptive to try and speed learning curve.
I drove the car only once before pulling the rearend to get it overhauled, the brakes where working, but didn't feel like they where working as good as they should. I had pulled the rearend for other reasons, not because of the brakes. (thought I had better mention that or you guys might really think I was a ding dong
I reinstalled rearend and went to bleed the brakes, I started bleeding in sequence from the wheel closest to the master cylinder to the farthest, (which I now know is wrong, I shoud have done it opposite, but I didn't know that till now.) I could get the fronts to bleed with good solid pedal, but couldn't get the rears to bleed (was getting very very little fluid to come out of the bleeders, and pedal would hardly move). I have blead the brakes on many cars and have never had problems, so I figured my combination valve might not be working. I cracked the line on it going to the rear...nothing. the valve was the cast steel one and very corroded. I ordered a new brass ac delco one from postons and installed. Same results. I then cracked the lines right off the master cylinder. The line for front brakes was working great (as I already knew since front brakes felt great), but the rear line wasn't pushing anything. So I figured the master cylinder was plugged somehow, (the fluid was a little dirty in the resevoir, and the whole vaccuum master cylinder assembly looks like it probably came from a another gbody car, another words, not new.) So I ordered a brand new master cylinder and installed. I blead the cylinder per the instructions.... until all air was purged from the clear hoses that came with the kit (routes the fluid back into both resevoirs). I then hooked up lines and blead in the same sequence from wheel closest, to farthest away,... and still same results. So I started doing some reading, and learned I should be bleeding them opposite due to the way the combination valve works. I had thought maybe I need to depress the button on the valve while I bleed since it says I may need to do that in my 87 buick service manual, but according to some previous post here, lots of you have never messed with that valve and blead ok.
I also checked the rear pistons to make sure they where free and clear and not pinched or slanted.
My 87 buick service manual says that in a conventional brake system, (disc in front, drum in back) I should bleed from farthest away from master cyinder first. Since my front brakes where free of air and firm, I figured I should crack the lines and pump them and put some air in them so they won't build pressure, and the combination valve will instantly send fluid to the rear. So I did that, and started to bleed from the farthest wheel away first, and got very little fluid with the brake pedal not going down hardly at all when I blead, same as before. I should also note, that when I went to bleed the right rear after I had installed the master cylinder, (before I knew of the bleeding sequence) that I got lots of fluid, and pedal went all the way to the floor, but when I went to the left rear, I couldn't get it to bleed.
I then went back to the combination valve and cracked the line going to the rear (to make sure that my rear lines wheren't maybe restricted or clogged somewhere), but it wouldn't bleed either.
So now I don't know what the heck to do. I've changed everything in the freakin system.
I have kept the resevior full, at all times, its never went empty.
I have put the cap back on, after every time I would top it off after bleeding.
I've never started the car, according to previous post, you'll always get a better blead system if you don't.
I have been correctly bleeding it, with one person pushing and holding brake pedal while I tighten the bleeder at each wheel, so's not to let air back in the system.
thats about all I can think of. anybody have any ideas? This car will be used as a daily driver. I want all 4 corners to be working as they should.
I know I got a lot of fluid that one time that I was bleeding the right rear brake, so it must be intermittant. It's a brand new mc, not refurbished, but, could be faulty. I'm going to crack the bleeders, tap the combo valve, top it off and let it sit for the night. I'll try again in the morning. I've lost my helper for the night, she's complaing that her legs going to be sore tommorow. 
I've replaced and checked and rechecked everything in the system. I bit the bullet, swallowed my pride and called my dad. He is retired general motors tooling engineer of 38 years. He came over, reviewed the system, and suggested we bypass the combo valve, we did, and got same results I've been getting. So now our only culprit must be the master cylinder. I showed him the old one I took off. He took it over to the bench and put it in a vise. I pushed in on the cylinder with butt end of a hammer while he checked for flow. We only where getting flow from the front brake resevoir. (which made sense pertaining to my problem I had). but how come I coud get both resevoirs to flow and bleed just fine when I blead the master cylinder on the car? He got out some paper and started drawing a schematic of sequence of events that the 2 pistons and 2 springs do as they travel through the manifold of the mc. I laid down on the floor and went to sleep, I've been awake since 5 am previous morning. About 10 minutes later he gets up and says he's found the problem. He had taken some measurements of the differant openings (holes) in the cylinder with a steel rule, and had determined that the rear brakes would never get proper metering of fluid/pressure and would cause liquid lock if there wasn't a specific sequence of filling the mc when bleeding the brakes, IF: the master cylinder had been removed and emptied of fluid. We then returned to the car and completely emptied the new resevoir I had installed. Filled the rear brake resevoir with fluid, and blead it with the front brake mc line off. Then blead the rear brakes at the cylinders. Success!! Finally! they started bleeding like the should. He then attached front brake mc line, then filled that resevoir, and we blead the front brakes. I've got no spongyness, and very little travel with the pedal before all four lock up. (their probably going to be a little too touchy now. 
