I understand and I appreciate the advise the money just isn't there right now, I know picking up a car like this you can't be cheap with things but I'm trying to make it work the best I can for the time being.

 

just save the money till you can afford to buy the good parts,
I know its expensive to put a new MC and booster into a car that might not even run that well or be worth much.
I saved for 4 months till I could afford to buy the parts, yep the car sat because i couldnt drive it without brakes.

I did this to my 82 Weissach, the brakes were awesome after the new expensive parts were installed, and at some point your going to look outside and see your 928 as a very expensive collection of new parts and thats exactly what the car is.

SO, you already saved up enough to buy bad parts.
how much more would it take to get the best.
Brakes are one system where cutting corners will not be noticed till they dont work,
then it will matter.

Good luck with your project

 

I've had problems bleeding brakes after opening up the system as you have. Seems that you've gotten a good bleed. I suggest driving it for a few days and then bleeding it again. The bubbles will break loose and collect and you'll get more out.

 

Please follow the "bench bleed" procedure I described above. Installing a new MC without following this guidance --will-- leave you with a spongy low pedal thanks to air in the chambers. Pedal bleeding, unless done verycarefully, risks leaving the forward MC piston stuck in the forward position with no eas way to get it to go back.

In some preverse wisdom, the master cylinder is one of the highest parts of the hydraulics in your car. There are other orphaned spots where air gathers and hides too. On later cars this includes the T on the rear footwell bulkhead forward of the battery, and effectively includes the cross-pipes in the rear. I don't know the exact piping configuration of the earler dual-diagonal cars, but someone will chime in. The perverse wisdom part is that conventional bleeding has us trying to push air bubbles downhill to the calipers, when they really want to stay in the high spots. If you find that you do in fact have air stranded in those high spots, you would try a good power/pressure bleed from the master cylinder. The velocity of fluid flowing through the system would hopefully entrain air as bubbles and carry them through the system to wherever you were releasing fluid. You can unbolt the calipers and suspend them high (coathanger wire from the springs) with the bleeder valve at the highest point as they are suspended.

The next option is a pressure-bleed backwards, after you've tried going forwards and failed. After the first forward effort, there is no air in the caliper chambers so pushing uphill only needs to move the air that's in the high spots in the piping. For this the calipers are supported low. The lines at the MC are removed and piped to a catch reservoir, MC ports are plugged. Good to do this immediately after bench-bleeding the MC, since the purge piping is still sealing the MC ports.

The last, most effective and hardest bleed to pull off (so to speak...) has a serious vacuum pump (with a liquid trap) connected to the piping at the master cylinder end, sucking all the air out of one section of the system at a time. Fluid is allowed to enter from the caliper ends. Use silicone grease on the bleeder screw threads or, better, a section of brake tubing and a hose you can pinch closed while evacuating. Hose end goes into the fluid bottle at each wheel for the system/section you are purging. Pull vacuum with a hand pump first on the caliper fill hose to fill it with fluid, pinch it off and connect to the caliper. Then full vacuum on the rest of the circuit from the MC end of the piping. Un-pinch the hose from the fluid bottle for a few seconds to fill the whole line, watching the liquid trap at the pump. When all are done, you can reconnect everything correctly, starting at the MC end. The line is now full of fluid and seled at the bottom end by the pinched hose, so you'll have an assistant put a little pressure on the pedal before you connect the pipe so there's no air bubble at the connection. Once all the MC piping is connected and the reservoir has fluid in it again, replace the temp hoses and piping at the caliper with the bleeder valves and remount the calipers. When all are restored, do a "normal" forward pressure bleed to get any possible bubbles out of the caliper chambers.

FWIW, the vacuum method is the only way I (read: last thing I tried) could get all the air out of my brake system components. Pedal is very firm, very high, and brakes work exceptionally well. I managed to get some air in during a normal annual fluid flush exercise (let the power bleeder reservoir get low), and paid the price with a low/soft pedal even after multiple pressure-bleeder attempts, the push method from low calipers, and vacuum bleeding with the hand pump. I ended up using the pump I use for AC evacuation. with the liquid trap from the hand pump kit protecting the pump. New vacuum-pump oil immediately after this fun process, by the way.

 

try pressure bleeder AND slow manual , old school bleeding. (two man technique).
it can be frustrating to get that one little bubble out of a rear line, for example and I if you don't get it, the entire system is compromised. its a little easier with the early cars, as there is only one bleeder on each caliper! furthest to closest don't forget.