replacing powermasters

[saltydog]

I'm ready to switch out my powermaster unit with one I'm going to get from autozone. Is this a difficult task? Are there are any special techniques or tools I'll need before I start? Should I attempt this myself or just have my mechanic do it?

 

[V6POWER]

You can do it yourself. Hardest part is bleeding the brakes.

 

[pacecarta]

the unit i got reccomends (insists actually) that you change the brake proportioning valve (down on the frame) to the new brass unit . gm# 25509419 about 42.00 at gmpartsdirect.com

 

[gofstbuick]

Originally posted by Look Quick
You can do it yourself. Hardest part is bleeding the brakes.

Actually bleeding the brakes is easy if you don't fill the PM assist reservoir until you've got the brake hydraulics in order. There are two small reservoirs and one large reservoir. The two smaller reservoirs are for braking and the large reservoir (with two holes on the floor) is for power assist. If you don't have a bench bleed kit, IMHO buy one. Install the PM assembly on the car, fill the two small reservoirs with brake fluid, install the bench bleed kit (with the hose immersed in the brake fluid) and pump the brake pedal until there is there is no bubbles in the brake fluid. The braking portion of the MC is now bled. Hook the brake lines up to the MC and bleed the lines at the combination valve. I assume the air is now out of the brake system, but if it make you feel better, you can gravity bleed the wheel cylinders and calipers. Now you're ready to tackle the PM assist bleeding. On the inside of the large reservoir is the fill line, fill the reservoir with brake fluid until it reaches the fill line, and turn the ignition on. The port (on the floor of the large reservoir) in front is the suction port. If the reservoir runs dry, fill it until it just covers the suction port. Do not let the PM motor run for more than 20 seconds. Turn the ignition off if the PM motor runs for more than 20 seconds. This is an indication there is air in the power assist side and you'll need to bleed the air out. This is accomplised by loosening the hose below the accumlator ball. Loosen the hose until fluid flows from the hose. THIS PART IS CAPPED FOR A REASON, SO PAY ATTENTION!!!!!!!. DO NOT UNDER ANY CIRCUMSTANCES COMPLETELY SEPARATE THE LINE FROM THE MASTER CYLINDER BODY, OR REMOVE THE ACCUMULATOR OR PRESSURE SWICH. THESE PARTS ARE SUBJECT TO OVER 700PSI OF PRESSURE AND WILL FLY AND MAY CAUSE GREAT BODILY INJURY!!!!!!!! After fluid flows from the hose, tighten it and turn the ignition on and allow the Pm motor to run and it should stop in less than 20 seconds, if not repeat the PM bleed process again. I doubt you would have to repeat more than once. Finally, put the cover on and test drive the vehicle. The vehicle should stop very well and the brake warning light should not illuminate. If it does, check the alignment of the brake swithes and bleed the brakes (not the PM motor side).