Brake problem- still squishy

[Paul Maurer 2]

I am trying to correct a problem my '05 has developed- about 20% of the time, my brake pedal will suddenly fail during a stop and travel to the floor as I press it, like it suddenly loses pressure in the system. The truck will still stop, but the pedal makes a strange sound and the pedal travels more than it should. I had the master cylinder replaced and the brakes bled, but it is still happening. Any ideas?

 

[Gavin Allan]

Loosing fluid level in the reservoir?

 

[Kevin Palmer]

Is the ABS light coming on?



Do you feel the pedal like kicking back at you, or just go down smooth?

 

[Paul Maurer 2]

No ABS light, fluid full and stable.

 

[James Kerr]

If you pump it when it goes loose does it build pressure again?

 

[Gavin Allan]

Sounds like another bad master cylinder. Pedal hitting the floor would have to be brake hydraulics, and no fluid loss would mean bypassing/leak inside the master cylinder. Now, if the pedal were dropping more than normal, but you still had braking ability, I would be looking at the brake booster unit as having an internal vacuum leak, etc.

 

[Larry Gamble]

Rather than start a new thread... I co-opt this one.



Anyone changed a Master Cylinder?



Left campus this morning, brake pedal went to the floor but I got some brakes at the bottom of the pedal travel. By the time I got out of traffic, I got the Check Engine Light and the brake light is on (low fluid). I haven't read the codes yet.



Fluid is almost gone. No sign of leaks at the wheels. I refilled the reservoir, it will build pressure but it dumps and the pedal sinks to the floor. And, it's loosing a bit of fluid.



I figure I've lost a seal in the master cylinder.

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[Jeremiah Morgan]

Sounds like both problems are a master cylinders!! Make sure and get the brake systems flushed!!

 

[trac-ho]

I am trying to correct a problem my '05 has developed- about 20% of the time, my brake pedal will suddenly fail during a stop and travel to the floor as I press it, like it suddenly loses pressure in the system. The truck will still stop, but the pedal makes a strange sound and the pedal travels more than it should. I had the master cylinder replaced and the brakes bled, but it is still happening. Any ideas?

having the same problem. pedal makes a weird noise, then just drops. i changed the master cylinder, but didnt seem to make a difference. any ideas?

 

[stunner67]

having the same problem. pedal makes a weird noise, then just drops. i changed the master cylinder, but didnt seem to make a difference. any ideas?

Your ABS module may be faulty if you don't have a leak anywhere.

 

[swshawaii]

having the same problem. pedal makes a weird noise, then just drops. i changed the master cylinder, but didnt seem to make a difference. any ideas?

Were both calipers removed when troubleshooting? Somewhat common issue is switching driver and passenger side calipers when the bleeders end up on the bottom. Impossible to purge all the air unless the bleeders are on the top. Pretty easy to visibly check the bleeders if you removed the calipers.

 

[Todd Z]

Bad wheel sensor or hub bearing causing the abs to kick in.