Brake booster

[morespeed69]

How do you tell if your brake booster isn't working correctly? I had a vacuum leak on my booster and after repairing I felt like the brakes where dragging. How do you test it while on the car?"

 

[dadaroo]

If you think your brakes are dragging you put it in the air and see if they are. Would not see how fixing a vacuum leak would cause dragging but you didn't explain exactly what you did to the booster.

 

[morespeed69]

If you think your brakes are dragging you put it in the air and see if they are. Would not see how fixing a vacuum leak would cause dragging but you didn't explain exactly what you did to the booster.

the vacuum line runs off booster i know the booster has dual diaphragms.What happens if one goes bad? Maybe not have enough pressure to retract brakes

 

[dadaroo]

Not sure of the internal design but if the brake booster was somehow affecting the retraction of the brakes then you should know that from the brake pedal position. You can try pulling up on the brake pedal by hand to test.

 

[94C4-Vette]

In my past life brakes were my forte. There is a vacuum pressure guage that you can use to test the booster. You may be able to rent it from a local autoparts store. Also you can look on line for your model car's brake specs for booster pressure. If you are unsure of what to do...take it to a well known local shop and ask them to help you or walk you through it. When one half of the booster is not giving you a good reading you will need to replace it. This is VERY RARE.

 

[morespeed69]

if I put my foot on the brake while the engine is running i turn off motor and my foot slowly goes to the floor. Then if I pump brakes I can hear the booster squeal every time I depress it. Any thoughts??

 

[dadaroo]

[h=2]Testing Booster[/h]

• Most power brake systems in autos are vacuum-based, using the difference between engine intake vacuum and atmospheric pressure as their power source. To test your brake booster, pump the brakes several times with the engine off to deplete stored vacuum. Turn on the engine while pressing lightly on the brake pedal. You should feel the pedal fall away a bit and then become firm, but not hard. If you feel nothing at the pedal when the engine starts, your brake booster is not functioning.
  
  

[h=2]Another Test[/h]

• Booster problems may indicate failure of the booster unit itself or problems in the vacuum system that powers the booster. A vacuum system problem may leave you with only partial boost. To test for vacuum problems, start the engine and run it to medium speed, then turn off ignition and take your foot off the gas. Wait about a minute and a half and then apply your brakes. You should feel the vacuum boost on at least two brake applications. If you do not, you may have a vacuum system leak or bad vacuum check valve.