1G Rear brake bleeding issues

[jamel16]

So here is the problem I’m having ,I can’t seem to bleed my rear brakes. I have a vacuum bleeder ( mityvac) and I also bought the one that uses an air compressor from harbor freight and nothing works. This is what my brake system consist of rebuilt 3000gt front calipers, rebuilt oem rear calipers, SS lines front and rear, Jnz abs delete kit, 3g brake booster, 3g master cylinder ( brand new), 1g oem proportioning valve ( brand new). For the life of me I cannot bleed the rear brakes, it feels like something is blocked or locked up. I attached the mityvac, applied vacuum to 25psi, cracked the bleeder and nothing happened. The gauge just stayed at 25 psi. I researched and found that this could be caused by a bad proportioning valve, so I swapped out my brand new one for a couple of used units I had laying around. There was no change. I performed all the bench bleeding processes by the book. I’m totally lost and frustrated on this one. Any help would be appreciated.

 

[1990TSIAWDTALON]

I just had to replace my whole rear brake lines. I had one bleeder that would not bleed. Took it out, drillled out the little hole (full of rust), then drilled out the center (wow, lots of crud) and finally that side bled fine. It had the caps on the bleeders too but they were still very bad. Got a clear water bottle, filled it half full of brake fluid, stuck a piece vacuum hose on the bleeder and into the bottle with brake fluid in it. With that setup, I could SEE the air bubbles coming out and it will suck fluid back in. A few pumps later, that side was done then I went to the other side and did the same. After that, I had help and did it the normal pressure bleed on both sides and they are rock solid.
SO....check your bleeders. I bet they are not bleeding. Parts store can fix you up with new bleeders also. Just what I did yesterday. Hope it helps. This was a 1gb car and i replaced lines from the prop valve all the way back to both rear calipers. (It takes 25' by the way)

Marty

 

[SasaniFab]

I just had to replace my whole rear brake lines. I had one bleeder that would not bleed. Took it out, drillled out the little hole (full of rust), then drilled out the center (wow, lots of crud) and finally that side bled fine. It had the caps on the bleeders too but they were still very bad. Got a clear water bottle, filled it half full of brake fluid, stuck a piece vacuum hose on the bleeder and into the bottle with brake fluid in it. With that setup, I could SEE the air bubbles coming out and it will suck fluid back in. A few pumps later, that side was done then I went to the other side and did the same. After that, I had help and did it the normal pressure bleed on both sides and they are rock solid.
SO....check your bleeders. I bet they are not bleeding. Parts store can fix you up with new bleeders also. Just what I did yesterday. Hope it helps. This was a 1gb car and i replaced lines from the prop valve all the way back to both rear calipers. (It takes 25' by the way)

Marty

Ahh replacing brake lines........ its the worst

 

[1990TSIAWDTALON]

Boy you know it!!!
I bought CNJ line which is copper nickle alloy and it comformed sooo much easier than normal line. It used all 25' of the coil but is almost perfect. I was surprised and would recommend that stuff to everyone!. Covered the line with rubber tube where they are in the wheel wells. Time and money well spent though. We all need to make sure the back half is as good as the front half.
You can see my dsm up on all 4's.

 

[jamel16]

I just had to replace my whole rear brake lines. I had one bleeder that would not bleed. Took it out, drillled out the little hole (full of rust), then drilled out the center (wow, lots of crud) and finally that side bled fine. It had the caps on the bleeders too but they were still very bad. Got a clear water bottle, filled it half full of brake fluid, stuck a piece vacuum hose on the bleeder and into the bottle with brake fluid in it. With that setup, I could SEE the air bubbles coming out and it will suck fluid back in. A few pumps later, that side was done then I went to the other side and did the same. After that, I had help and did it the normal pressure bleed on both sides and they are rock solid.
SO....check your bleeders. I bet they are not bleeding. Parts store can fix you up with new bleeders also. Just what I did yesterday. Hope it helps. This was a 1gb car and i replaced lines from the prop valve all the way back to both rear calipers. (It takes 25' by the way)

Marty

Tried everything you mentioned and still no luck. Blew out the lines just to make sure I didn’t have any blockages. I’m leaning towards I may have bought a defective proportioning valve. I hope not cuz that’s 100.00 bucks down the drain. I may try a pressure bleeder but I’m out of choices right now.

 

[1990TSIAWDTALON]

Well dam... no pressure at all to just the rear??
Could the MC be going out or is it good?

 

[1990TSIAWDTALON]

Crack the input line at the prop valve and check for fluid flow.....have rags ready.

 

[jamel16]

MC is new, bought both the MC and proportioning valve at the same time. What’s strange is when I removed the lines from the prop valve, fluid instantly started flowing out. I may just open all the bleeders and try the gravity method. The car has been sitting a number of years with no fluid in the lines.

 

[EVLGSX]

I would try that. Take a brand new bottle of brake fluid, leave the foil on under the cap, just poke a small hole in it, but not too small, like 1/4''. Then put it in the reservoir upside down. Put a piece of line on each bleeder running into a pan. First crack the fronts only and let it sit until you get consistent solid drips. Close the fronts, and now crack the rears. Then just wait. After theyve been dripping good for a while you should be good. You can follow this up with pumping with a line into a cup of fluid to confirm that you got all the air out,like stated above, but you really shouldnt need to. If that does not work, you must have a blockage somewhere.

 

[jamel16]

Well I got some relevations, fluid is actually starting to flow out of the brake lines. Bad thing is one rear brake line is damaged and needs to be replaced. I’m wondering should I do both while I’m down there. I’m definitely dreading this job