Brake pedal hits the floor

Jerseydog

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Nov 5, 2020
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I have a 2012 JK and when you have to hit the brakes real hard they stop but the pedal goes to the floor. The pedal comes back to working normal and they do not pull. I'm thinking it could be the master cylinder but not sure. Does anyone have any ideas? Thanks Jerseydog
 
Have you recently changed the brakes or anything? I'd start by checking your brake fluid level and seeing what color it is. Then I'd look at the master cylinder.

When is the last time you changed the brake fluid?
 
Hard braking would lock up the brakes as it did with our jeep. But with the peddle going all the way to the floor would indicate that you could have a leak in the system or worse a brake hose could have ruptured. if the brakes had been repaired or upgraded at some point, they may have neglected to bleed the brakes, which would leave air pockets in the system.

Also, your avatar seems to indicate that you travel with a very large trailer. if you have not upgraded your brakes, it would be suggested that you do so.
 
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To me that reads as not properly bled brakes, air in the lines.

when parked can you just slowly push the brake pedal all the way to the floor?

As stated earlier check the fluid reservoir to make sure it's topped off and you are not the one putting air in the lines by not having enough fluid.
 
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Thanks for the reply. did brakes not to long ago. I'll try bleeding and see how that works. Trailer only weighs in at 2300 lbs. If anyone is interested it pulls very nicely.
 
Brake pedal goes 50% to the floor on parking, engine off, and brake pedal going 100% to the floor with some pressure when engine running(pressing on pedal not soft, and not hard).
This is normal?
I think brakes to soft, but wheels will block if I pressed pedal hard
 
Is your brake fluid low, a small leak could do that?

Also air in the brake system or a bad vacuum booster.

Did this just happen like overnight?
 
I bought a car recently, so it was. I bled the brakes in the standard way, manual, starting with the rear passenger. Then I bled the ABS through diagnostics.

I asked at the local Wrangler club and a couple of guys wrote that they had the same brake pedal behavior.
So I'm confused - is it supposed to be like this, or is it still a malfunction?
On another forum, a person who has a JK CRD 2.8 said that he made a request to the manufacturer, and the manufacturer replied that this is normal pedal behavior, and this is how it is configured in order not to ruin the brake line, and to keep the brake fluid pressure stable.
 
I monitored the value of the pressure sensor through diagnostics, and the value with the engine turned off reaches 65-70, when the pedal is pressed very hard, it is pressed 50% to the floor.
When the engine is on, the pedal is pressed 100% to the floor with force, while the pressure value is kept at 110.