Vacuum Brake Converted-Hard Brake Pedal
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John Larkin
Sublime Master of Turbology
- Joined
- May 25, 2001
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- 4,994
Big spurt is bad. Read this article:
Follow a Diagnostic Process When Curing a Low Brake Pedal, Bill Williams, Brake & Front End, June 2001
Ignore the title of the article, it's not the point. The part about the quick-take-up valve is. This may not be your particular problem but it very well could be.
Also adjust your parking brake so it is fully engaged at 3 clicks of the e-brake pedal. Proper adjustments help.
FYI, I had the same problems as you. Now I can hold 15psi no problem.
Follow a Diagnostic Process When Curing a Low Brake Pedal, Bill Williams, Brake & Front End, June 2001
Ignore the title of the article, it's not the point. The part about the quick-take-up valve is. This may not be your particular problem but it very well could be.
Also adjust your parking brake so it is fully engaged at 3 clicks of the e-brake pedal. Proper adjustments help.
FYI, I had the same problems as you. Now I can hold 15psi no problem.
POWERBRAKEBOB
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Hydroboost Conversion
20" Of Vacuum Is Hard To Get On A Turbocharged Engine. That's Why Buick Did Not Put The $12.00 (at O.e. Cost) Vacuum Booster On Their Turbo Charged Cars. No Worky...the 83-85's Came With A Hydroboost, And Then They Tried The Powermaster On The 86-87's As An Experiment. No One Knew How Long They Would Last. G.m.'s Warranty Is Not For 20 Years. Blowing Air Pressure Into A Vacuum Booster Does Not Work. Pressure Is The Opposite Of Vacuum. Some Guys Have Blown The Hose Off Of The Check Valve, Or Blown The Check Valve Apart. No Booster! Buick Gets Sued For Those Kind Of Problems. The Hydroboost Runs Off Of The Power Steering Pump, And Needs No Vacuum. It Doesn't Care If The Engine Is Under Boost At All Times. It Will Deliver Up To 2000psi To The Calipers, At Idle Pump Speed. The Vacuum Booster, With Little Vacuum, Puts Out About 800psi. Our Hydroboost Bolts Right On, Uses The Same Pedal As The P/m, Lasts 200,000 Miles, And The Master Is Replaceable By Itself. If The Pedal Was Not Changed With The Vac Booster, It Will Break The Plastic Valve Body Of The Vac Booster, And It Will Have A Wide Open Vacuum Leak, This Also Causes Problems With The F.i. Metering. The Broken Valve Body Will Give The Hard Pedal. Tee'ing Into The Pcv Ports Is Connecting The Vac Booster To The Constant Leak Of The Pcv Valve. Too Many Problems With The Vacuum Booster Conversion On This Car.
20" Of Vacuum Is Hard To Get On A Turbocharged Engine. That's Why Buick Did Not Put The $12.00 (at O.e. Cost) Vacuum Booster On Their Turbo Charged Cars. No Worky...the 83-85's Came With A Hydroboost, And Then They Tried The Powermaster On The 86-87's As An Experiment. No One Knew How Long They Would Last. G.m.'s Warranty Is Not For 20 Years. Blowing Air Pressure Into A Vacuum Booster Does Not Work. Pressure Is The Opposite Of Vacuum. Some Guys Have Blown The Hose Off Of The Check Valve, Or Blown The Check Valve Apart. No Booster! Buick Gets Sued For Those Kind Of Problems. The Hydroboost Runs Off Of The Power Steering Pump, And Needs No Vacuum. It Doesn't Care If The Engine Is Under Boost At All Times. It Will Deliver Up To 2000psi To The Calipers, At Idle Pump Speed. The Vacuum Booster, With Little Vacuum, Puts Out About 800psi. Our Hydroboost Bolts Right On, Uses The Same Pedal As The P/m, Lasts 200,000 Miles, And The Master Is Replaceable By Itself. If The Pedal Was Not Changed With The Vac Booster, It Will Break The Plastic Valve Body Of The Vac Booster, And It Will Have A Wide Open Vacuum Leak, This Also Causes Problems With The F.i. Metering. The Broken Valve Body Will Give The Hard Pedal. Tee'ing Into The Pcv Ports Is Connecting The Vac Booster To The Constant Leak Of The Pcv Valve. Too Many Problems With The Vacuum Booster Conversion On This Car.
I know you are probably past this, but I felt you should know...
Response time of a properly functioning P/M is far superior to the response time of any vacuum system I have ever driven. The P/M has over 600psi of pressure in reserve the instant you touch the pedal - and your engine doesn't have to be running to have this. A vacuum system has to build it's pressure from 0psi. The biggest problem the fcty brake setup has is undersized front brake rotors.
You vacuum conversion will never be as good as a stnd vacuum system unless you setup a vacuum pump independent of the motor. As Bob has said, a turbocharged motor will never create the proper vacuum source.
Also, the reserve capacity of the vacuum booster is about 2 or 3 pumps. The PowerMaster has close to 10 pumps reserve.
HTH
Z
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