how to test a brake booster

[azzzuki]

how do i test my brake booster???? on my fj80/1991

Thanks

 

[colsoncj]

my general rule of thumb has been if you have brakes, but they feel like manual brakes, you have a booster issue... if you've got other symptoms, you have other problems.

 

[dgangle]

couple ways

1. pull ~20"Hg with a manual pump and see if it holds
2. put a gauge in between the booster and the check valve, run the engine, turn off and see if the vacuum holds
3. procedure outlined by CCoT Brake Booster Working?

froogling "testing a brake booster" hit something like 10,000 sites. That should be your first try

 

[azzzuki]

couple ways

1. pull ~20"Hg with a manual pump and see if it holds
2. put a gauge in between the booster and the check valve, run the engine, turn off and see if the vacuum holds
3. procedure outlined by CCoT Brake Booster Working?

froogling "testing a brake booster" hit something like 10,000 sites. That should be your first try

i thought it was a sealed unit and it will keep pressure no matter what??????

 

[dgangle]

not if a diaphram or two leak!

google 'brake booster' and read up

 

[motorcoach123]

The guys at the brake shops used to pump the brake pedal with the engine off, exhausting all the vacuum, and then with your foot still on the pedal, start the engine, when the vacuum builds up, the pedal should sink somewhat.
FWIW

Gord

 

[gotmud]

Happy reading...

 

[cjhollenshead]

The "vacuum hold test" is just a test to check your vacuum check vlv. This is the most common culprit, but will only effect reserve braking I:E braking with the engine off. An easier way to check it is to run the engine for a minute, shut it off and pull the vacuum line off the booster. If it obviously sucks air in then the booster and the check valve are good to go.

 

[cjhollenshead]

One more thing, can you hear the booster "hissing" inside the cab? If so thats deffinatley a bad booster.

 

[dgangle]

...and a burnt exhaust valve or two a short time thereafter!