Brakes go to floor

[JMO413]

So it's not a Jeep but this is the only place I know to get real technical answers. I'm working on my mom's 1996 Geo Prism. There brake pedal goes straight to the floor and just barely work. My guess was master cylinder so I changed that. I bleed all four corners starting in the passenger rear. I vacuum bleed them first and got a full container full from each one.

One of these full from each bleeder. The I did the normal pump and bleed with my wife in the car. The pedal feels good when the car is not running. When you start it the pedal goes to the floor still. If I unhook the vacuum from the booster the pedal doesn't drop to the floor. So do I replace the booster? I thought a bad booster would be a hard pedal. Any thoughts would be appreciated.

[jeeptec1]

Failed master cylinder


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[JMO413]

Brand new master cylinder that I bench bleed and got good fluid flow from.

[Jeep Driver]

This is why I have always bled with the engine running........I want to know what's going on, how it feels, in it's working state. 

 

 

Sounds to me like a bad booster as you noted......but........you are there and I can only guess. 

[JMO413]

6 minutes ago, Jeep Driver said:

This is why I have always bled with the engine running........I want to know what's going on, how it feels, in it's working state. 

 

 

Sounds to me like a bad booster as you noted......but........you are there and I can only guess. 

Thank you. Just looking for opinions. Got a booster coming. Hopefully that does it we will see.

[JMO413]

Booster was bad guts were pushed out the front.