Hydroboost Vs Vacuum Vs Powermaster
I Was Refering To Residual Check Valves Used In The Outlet Ports Of The Master Cyl, Not The Check Valve Used To Hold Pressure In The Accumulator. Different Things. The Thing I Have Put On This Site Is About The Fact That Buick Never Used A Vacuum Booster On Their Turbocharged Cars. The 83-85's Came With A Hydroboost. No One Here On This Forum Has Ever Complained About The Performance Of Those Hydroboosts, Even Though They Are Close To 25 Years Old. They Still Work! Why Is It So Hard To Believe That They Would Not Work On Any Other Car Including The 86-87 G.n.'s? Vacuum Boosters Need Vacuum. They Need 20" Of Vacuum To Achieve Their Rated Output. The L88 Corvettes All Had Vacuum Power Brakes, Needed To Stop The Car At 160mph, But They Had To Downshift With A Closed Throttle To Get The Needed Vacuum. Chevrolet Discourged Street Drivers From Buying L88 Cars To Go To Work In, Because There Was Not Enough Vacuum At Idle Speeds To Push A 1.125" Master Used On Power Disc Brakes. Manual Masters, Putting Out About 600-800 Psi With Heavy Foot Pressure, Could Not Stop A 4 Disc Corvette At High Speed. They Put Boosters On Those L88's. Supercharging A Vacuum Booster Was Not A Good Idea, Then, Or Now. If You Clamp The Hose Down Tight Enough To Keep It From Blowing Off The Vac Check Valve, Then, If, The Rubber Valve Inside The Check Valve Was Pushed Into The Vac Booster, The Vac Chamber Of The Booster Would Be Subject To Manifold Pressure. The Surface Area, And The Cubic Inches Of Area Inside The Vacuum Booster, Even Under 20lbs. Of Boost, Would Be Enough To Blow It Apart, Causing Catastrophic Failure. It Would Be Like Sticking A Shop Blow Gun Inside A Vacuum Booster. It Would Blow It Apart. So, You Say, I Will Use An Electric Vacuum Pump. O.k. Look Inside The Suction Port. It Might Be About 1/8th To 3/16" In Diameter. Now, Look At The Volume Of Air Needed To Evacuate The Delco Booster, Every Time You Apply The Brake. Besides The Noise Of The Pump, The Elec Pump Cannot Pull The "volume" Of Air Out Of The Booster, To Meet Traffic Needs. It Takes A While For The Pump To Catch Up. Every Time You Apply A Vacuum Booster, You Let Air Into The Rear Of Both Diapragms. When You Let Up , That Air Has To Be Sucked Out By The Engine, Or The Pump, To Equalize The Vacuum On Both Sides Of The Dias., To Release The Brakes. That Air, Momentarily, Drops The Vacuum Inside The Booster To 5-9" Of Vacuum. If You Need To Reapply The Brakes, The Vacuum Has Not Recovered To Give You The Assist Needed. Then The Hard Pedal. As Far As The Powermaster, Those Electric Motors Have Always Been The Weak Link. They Are Pumping Brake Fluid Under High Pressure. Brake Fluid Has No Lubrication To It. The Vanes Wear Out, And The Seal Wears Out. If The Seal Leaks Brake Fluid Into The Motor, It Shorts It Out. If The Plastic Vanes Wear Out, The Pump Cannot Achieve The High Pressure Needed To Charge The Accumulator, Thus The Hard Pedal With The P/m
The new accumulator did not fix it and the pump continues to run. There is a new MC on there, so all that should be good. I took the line lock out of the loop and that did not fix it. 
