Thought Master cylinder was the problem of brake pedal slowly going to floor

WARD B

MEMBER
2011 JEEP WRANGLER
3.8L
V6
4WD
AUTOMATIC
70,000 MILES

Thought master cylinder was the problem of brake pedal slowly going to floor after about 10 seconds of light pressure. Replaced master cylinder and bled the brakes and it still does it. No leaks at calipers or brake lines or loss of fluid from master cylinder.

5 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good afternoon,

Does the pedal pump up and stay hard?

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

How did you bleed the system?

You will need a scan tool to bleed the ABS module. Standard bleeding will not get the air out?

I would pressure bleed it. not vacuum or pedal bleeding.

Roy

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Monday, February 10th, 2020 AT 12:41 PM

WARD B

MEMBER
3 POSTS

Hi Roy,

The brake pedal is hard when first applied like when stopping at stop sign. Then light pressure while holding Jeep on flat ground it will slowly go down to the floor after about 10 seconds.
I bleed with vacuum RR, LR, RF, LF.
Guess will have to take to shop, the scan tools I have will not access ABS module.
Would calipers leak fluid by?
I plugged off the ports that come off the master cylinder with the plugs that came with new master cylinder for bench bleeding while on Jeep and pedal was hard as a rock so don't think it's the master cylinder.

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Monday, February 10th, 2020 AT 1:05 PM

ASEMASTER6371