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

Tiny
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.
Monday, February 10th, 2020 AT 12:28 PM

5 Replies

Tiny
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
Tiny
WARD B
  • MEMBER
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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
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
If they did, it would leak externally.

I believe you have air in the system.

Roy
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Monday, February 10th, 2020 AT 1:52 PM
Tiny
WARD B
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Okay, thanks Roy. Will try pressure bleeding them.
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Monday, February 10th, 2020 AT 1:54 PM
Tiny
ASEMASTER6371
  • MECHANIC
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You are welcome.

Always glad to help.

Roy
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Monday, February 10th, 2020 AT 2:27 PM

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