There are a couple ways to attack this problem, and what most people don't understand is that the powermaster system has two completely separate systems.
From here on out I'll refer to them as the inboard side and the outboard side.
The inboard side is the powermaster's booster side that generates the power assist to the master cylinder. The accumulator is part of it, along with the pump and pressure sensor, and the inboard side of the reservoir holds the fluid for this section, and if you'll look, you can see that the inboard and outboard sides are totally separated.
The outboard side of the reservoir and master cylinder are like any other standard hydraulic braking system on cars. You bleed the brake system and outboard section using the same technique that you would use on any standard hydraulic brake system, BUT....... With the key OFF!!! You have NO need for the motor/pump to be cycling while you're doing a normal brake bleed technique.
Now, with all that said IF any air gets into the inboard PM section/reservoir you could have some issues, like a noisy pump, etc. The inboard side is commonly referred to as self bleeding, and for the most part it is. But there is a procedure for bleeding the inboard side. Of course you do all these bleeding procedures with the reservoir cover off so you can see what you're doing. Now, turn the key off, and start depressing the brake pedal slowly (so the fluid doesn't squirt out the top of the reservoir) as far as it will go. Keep repeating this (10-15 times) until the pedal gets real hard and wont hardly move. You'll see the fluid in the inboard side rising to near the top (be careful).
See any foamy looking air in the inboard fluid???? If so, go watch some more TV and let the bubbles completely disperse. When the fluid on the inboard side is air bubble free, turn the key on and the pump will run and re-pressurize the PM side. Now do the same procedure again. Keep repeating this until you can de-pressurize(power off pedal pushes) the PM side and not generate any air bubbles in the reservoir.
You'll notice that when the system is pressurized (power on) that the inboard reservoir is only about half full. this is normal. The only time it should be near full is when you've pumped the system down to depressurize (power off pedal pushes) it.
Also take note of the fill marks on the Outboard side of the reservoir. Don't let it get below MIN during normal operation and it doesn't need to be near the top either!!!!!!.
So, to properly replace the accumulator, depressurize the system (power off pedal pushes). Put a rag under the accumulator, unscrew it, screw the new accumulator into place. Turn key on to pressurize the system. Turn key off, depressurize the system to see if there's any air bubbles showing up in the inboard side like described above, bleed as required in accordance with above procedures.
After you've got the accumulator replaced and you still have a spongy brake pedal, then the rest of the system needs to be bled as a normal car would be as stated early in this post.
