Powermaster To Vacuum Brake Conversion
Joe Baldwin
If your are having problems with your 87GN (other years and the T-Type may be similar or exact, but I don't have a clue) PowerMaster and want to fix your braking problems forever, read on. However, if you feel you must keep your car 'stock' like the general made it, you probably should skip this post.

I tried to fix my powermaster hereafter referred to as slugmaster, new accumulator, relays, swithes etc. None provided a real, long term escape from the brakes from hell! My dent in the garage door jamb and several other motorists that I scared the life out of would agree.

This fix cost me less than $85.00 and four hours labor. Now my GN brakes work better than EVER!Another Powermaster To Vacuum Brake Conversion

Tools Needed
For tools you should have the following:
  • an air ratchet
  • 15 mm deep socket
  • 18mm short socket
  • 10mm short socket or nut driver
  • pliers
  • screw drivers
  • knife
  • Jack and jack stands
  • right size wrench to fit the bleeder valves
  • A vacuum test pump Lisle or equivalent is useful but not absolutely necessary
  • A turkey baster or piece of tube to siphon out the old brake fluid is helpful too.
Go to the salvage yard and buy these things (you can find the new part numbers for new GM elsewhere). You need the master cylinder, vacuum booster and brake pedal (the vacuum pedal has more leverage). Easily available from 86/87 Monte-carlo and non-turbo Regals. My cost was $75.00, yours may be even lower. New parts would be about $150 from NAPA plus the pedal.

Buy a NEW GM style vacuum check valve for the booster, about $4.50 at checker, autozone, napa. Unless you are 'big time racing', I don't think you have to worry about boost damaging the valve. Get two feet of 5/16 gasoline hose and a plastic "T" that works for 5/16 hose. Also get some fresh DOT3 or 4 brake fluid. I don't recommend silicone fluid.

    I would highly suggest that you use a new vacuum check valve. My old one passed the tongue test, but it was still no good. Also, I used my hand vacuum tester to check that the 'booster' would hold a vacuum. It should be able to hold what ever vacuum your hand pump will apply. Whether you buy new or used, it would pay to check it out BEFORE installation. It is just too much work to take a chance with a bad part.

Place the turbo in a suitable work area, you will have to jack up your car to bleed the brakes, so do this on a level, safe area.

It takes about 1.5 hours to remove the old pedal and slugmaster.

1. Remove the Positive + Red battery cable! ! ! ! !
2. Using the turkey baster, pump, or short piece of hose (don't use the new fuel line I ask you to buy!) drain as much of the old brake fluid out of the slugmaster as you can. It will keep the inside of your GN and the paint looking better, longer.
3. Removal of the brake pedal is tricky.
a. Lay the driver's seat down in recline mode.
b. Your head will rest on the floor looking up under the dash, try to keep your feet off the headliner. Using needlenose, duckbills or pliers, remove the clip that retains the slugmaster piston shaft to the pedal
c. Use of an air ratchet makes it easy to loosen the pedal pivot bolt, use an 11/16" (an 18 mm will work, but it is loose) short socket.
d. Use a 5/8 openend (a 17mm will work) the other end from turning.
e. When the pedal comes out, there will be a number of parts to locate. The bolt and nut, two plastic bearing inserts as well as a piece of tubing that fits between the plastic bearing inserts and the pedal assembly.
4. I had to disconnect the speedometer cable at the joint right under the slugmaster.
5. After the powermaster, there is an adapter that must also be removed from the firewall. It has four mounting nuts (15mm) that must be removed from inside, way up under the dash. Use a 15mm deep socket and a 12" extension and use a flexible joint(3/8 drive). With air tools, about 3-4 minutes and you will have all of them on the floor.
6. Dress all of the wires, hoses etc away from the opening to install the new (or used as I did) montecarlo or non-turbo master cylinder and booster.
7. The booster mounting nuts must be re-installed from the inside with the same tools used to remove in step 2c.
8. The salvage yard from which I bought my old MC had not drained the MC, neither did I, and the lines are a direct fit. There was no requirement for any adapters etc. Did not even have to bleed the brakes.
9. Don't forget to re-connect the speedometer cable.
10. Put the new pedal from the salvage yard in in the same manner that the old one came out. It seemed easier to put back than take out! (Hint) Put the bushing and plastic bearings in the brake pedal assembly. Wrap a piece of masking tape around the pedal and over the end pieces to keep it all together so the loose bushings will not fall out when you try to maneuver it into place it up under the dash. BEFORE you attempt to re-install, take your knife and pierce the tape through the center of the bushing holes and carefully slide the bolt through the tape. If you do it right, you will have tiny pieces of tape holding the bushings in while not obstructing the bolt hole. This makes installing the pedal a piece of cake.
11. Put the Push ROD from the booster onto the stud on the newly installed pedal. Re-install the clip.
12. Connect up the vacuum source. I used a plastic 5/16 "T" to connect the vacuum between the vacuum port on the throttle body and the pvc valve. I ran the hose between the back of the throttle body plenum and the coil pack straight to the port on the booster. If The hose were the same 'age' as the rest of the underhood stuff, it would not be visible. Everything looks very 'normal' and un-obtrusive. It has been suggested that you use small hose clamps (#4 I think) to prevent engine boost from blowing off the lines. I recommend you change the PVC valve while you are at it.
13. Take appropriate action with your brake fluid, refill, bleed etc if required.
14. Place your old slugmaster in a cardboard box and place it in the 'long term' storage facility you employ. Keep it for at least 3 years, so when you throw the darn thing out, you will have the satisfaction of knowing that you kept it long enough to know if you made a good decision to upgrade (down grade if you will) your brakes. Be sure to write Powermaster, keep until 1998 on the container. This is because you will likely never have anymore brake problems and will therefore totally forget all about what a powermaster is and the date will make you feel like it is ok to throw it in the rubbish.

It took about 1.5 hour to re-install the vacuum parts. 1/3 of the time was spent looking for the right stuff to plumb and connect the vacuum.

By the way, I am a very large man, 6-2 and 245 and the only 'tight spots were when putting the bolts in to the pedal and they were by far not the worst situation I have had under a dash.

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