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Mustang Power Brake Booster testing
See Step 7 for Master Cylinder Test.
Testing Power Brake Booster
Step 1 – Testing the check valve
remove the vacuum hose from the manifold or back of Carburetor.
you should be able to suck air out but not blow in. If so check valve is good
Step 2 – Check that the vacuum hose is in good condition no cracks or leaks.
Step 3 – Vacuum test
attach hose back to manifold or carb. Remove from check valve side.
using vacuum gauge test for vacuum with engine running 14-18 expected.
Step 4 – Booster testing 1
Start engine allow booster to build pressure for a minute
With foot on pedal turn off engine. The pedal should hold for 30 seconds. If pedal comes up toward you air is escaping the Power Booster
Step 5 – Booster testing 2
With engine off apply foot to brake peddle. Start the engine pedal should only sink slightly.
Step 6 – Booster testing 3
Start engine. Allow pressure in Booster to build for a minute
Shut off engine and you should feel 3 brake assists.
Step 7 – Master Cylinder Test
Pump up the pedal 3x. Hold down for 15 sec. Pedal should not move. If moves down Master cylinder has leak.