Gilli Posted July 27, 2010 Share Posted July 27, 2010 (edited) Ok.. here are the deets: 1978 280z w/ SU's Front Disk, Rear Drum 1. When I bought the car, braking would be non existent until the pedal reached near the floor, then it would lock up. I found out that I was missing the Reaction Disk. Reaction disk is now permanently in place on the back of the push rod. 2. After a complete motor build about a year later, it's almost time to get this thing on the road. So I go to inspect the brakes and the pedal is a sponge, and goes to the floor. So I figure, time to bleed the brakes. The front brakes flow very well when I bled them and there was very few bubbles. I proceeded to the rear drums. I was getting very little fluid on both sides. No where near the flow as the front brakes. Why is this?? The fluid in the MC is full. There are no signs of leaks from the proportioning valve. **** I found out I was missing the check valve in between the booster and the intake manifold. How much of a different would this make? (P.S. - Just ordered it so it's on the way to be installed) 3. Here's the kicker. -Front Left Brake: Works perfectly -Front Right Brake: Slight grasp as the pedal is on the floor.. but still easily able to turn the wheel. -Rear Left Brake: No braking at all -Rear Right Brake: No braking at all 4. There is not a single leak that I can see anywhere, and the MC is full of fluid. Pumping the brakes and the MC fluid level stays the same. So I don't see why hardly any fluid is getting to the rear drums! I don't think I left anything out, If I did please let me know. Any help will be greatly appreciated. THANKS!! Edited July 27, 2010 by Gilli Quote Link to comment Share on other sites More sharing options...
Challenger Posted July 27, 2010 Share Posted July 27, 2010 Was there fluid in the MC while the car was down? Did you have to fill it back up after the engine rebuild? Quote Link to comment Share on other sites More sharing options...
Gilli Posted July 27, 2010 Author Share Posted July 27, 2010 Yes there has always been fluid in the MC.. P.S. - The fluid I pulled from the rear right bleeder screw was clean fluid.. couldn't be contaminated. Quote Link to comment Share on other sites More sharing options...
jt1 Posted July 27, 2010 Share Posted July 27, 2010 Try bleeding both screws on the master cylinder first, then the front brakes, then rear. Sometimes when a car has sat a while, or the system has been opened, it may take a couple of quarts of fluid to get all the air out. The check valve shouldn't make any difference. jt Quote Link to comment Share on other sites More sharing options...
Gilli Posted July 27, 2010 Author Share Posted July 27, 2010 Try bleeding both screws on the master cylinder first, then the front brakes, then rear. Sometimes when a car has sat a while, or the system has been opened, it may take a couple of quarts of fluid to get all the air out. The check valve shouldn't make any difference. jt Ok.. I'll give that a go. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 27, 2010 Share Posted July 27, 2010 Brake pressure switch below the MC on either the front fender or the firewall. Its got a shuttle valve inside that moves to close off the circuit (front or rear) that has the lowest pressure when a pressure differential of about 200 psi exists. You must gravity bleed the entire brake circuit before staring any brake bleeding. Quote Link to comment Share on other sites More sharing options...
emoximuu Posted November 5, 2010 Share Posted November 5, 2010 Hate to bring up an old topic but it applies and is the only thread I've found similar to my issue. No rear brake pressure. I bled the MC, worked great. Started gravity bleeding the system, started with the drivers front, ok, cool. When I got to the right rear, no fluid, poo. So I began checking the various components, got pressure on the rear side of the pressure regulating valve. Attempted to check for flow after the T fitting but rounded it off and didnt want to press my luck without a hose wrench. So what/where should I do/look at next? I thought to just replace the pressure reg. and pressure diff. switch but struck out finding any new or rebuilt, is it safe to remove them? Quote Link to comment Share on other sites More sharing options...
ukcats07 Posted April 20, 2011 Share Posted April 20, 2011 dragging this one from the depths I'm having the same issue as the OP. When I bleed the front brakes with my pressure bleeder I get great flow, no air etc. Put the pressure bleeder on the rear and I get nothing, not even a drip, out of the rear drums. I pulled the dual circuit pressure differential switch off and moved the pin to the middle and re-checked the system. With about 15 psi on the power bleeder I get flow on both sides of the differential switch and both sides of the pressure regulating valve. So I know that fluid is flowing past the valve and down the line to the rear of the car, however I still get nada out of the bleeders! What else am I missing here? I even put about 10-15psi on the bleeder and kept it at that pressure for about 10 minutes and I still got nothing out of the rear bleeders. Potential line blockage somewhere? Quote Link to comment Share on other sites More sharing options...
xplosiveg06 Posted April 20, 2011 Share Posted April 20, 2011 i had that problem on my left rear when i started fixing it up. it turned out to be the rubber hose line was clogged. 9 dollars to replace it and it flowed perfectly Quote Link to comment Share on other sites More sharing options...
ukcats07 Posted April 21, 2011 Share Posted April 21, 2011 i had that problem on my left rear when i started fixing it up. it turned out to be the rubber hose line was clogged. 9 dollars to replace it and it flowed perfectly Looks like this might be the problem. I disconnected the the rubber hose at the drum and had no fluid while under pressure. I then unhooked the hard line from the rubber hose at the top side and the fluid started flowing from the hard line. Now if only the local places had this line in stock... Quote Link to comment Share on other sites More sharing options...
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