How do I troubleshoot a master cylinder?

[Habbibie]

Just curious how do some of you guys go about troubleshooting a brake master cylinder? & if possible the ABS pump also?

EDIT: forgot to mention it's a 2005 expedition 4x4 XLT w/ABS & W/O AdvanceTrac, 140k miles.

I'm suspicious that mine is failing but I want to confirm before repairing or replacing,

Recently a broken brake line was replaced (few months ago) fast forward to now and theres no leaks visible anywhere and the resviour is been full since.

My brake fluid is dark blue ~ almost black, while driving the first 75% of travel doesn't engage the brake till almost at the very end of the pedal travel. It does max out easily and I've hit it to the floor at times. While I'm idling in D or P it acts normal with pressure felt as soon as I touch the pedal

Any help is highly appreciated

 

[1955moose]

Well the way we used to go master/vs wheel cylinder or caliper, was at a stop holding constant pressure after pumping 3 times, was if it slowly sank, that was master. If it held it was wheel cylinder if drum, or caliper if disc. That being said, with abs, and modules and such, I'd start with a abs codes check. Your not losing fluid, I'd bet you picked up air somehow. Your last comment it feels normal at idle, rules out the master. It would drop the pedal all the time. Hey Habbibie didn't we have a guy here about 2 months back that had to replace his abs pump! Similar symptoms wasn't it!

Sent from my N9131 using Tapatalk

 

[Habbibie]

Hey Habbibie didn't we have a guy here about 2 months back that had to replace his abs pump! Similar symptoms

Do you think you can remember the name or the title of the thread? I must've missed it

 

[1955moose]

I don't, maybe one of our regulars can pull it up. I work with just a basic Android, and am not real techie like others. I'll dig around though. Stamp or Bedrck might remember it.

Sent from my N9131 using Tapatalk

 

[Habbibie]

Stamp or Bedrck might remember it

I'll PM stamp cause the term ABS doesn't pull out anything in the search, bedrck47 God rest his soul... remember he's no longer with us.

 

[1955moose]

He passed away, wow I didn't know that. I liked that guy, he used to pm me everytime I screwed up. Just watched a video online that symptoms were just like yours, was Abs pump. Theirs a way to reroute master cylinder bypassing pump to see if pedal gets hard. You might try that first. The pumps rarely fail, but your year is I think same if not close to the other members that did. Can't believe you've been driving with sinking pedal! When did Bob pass away?

Sent from my N9131 using Tapatalk

 

[Habbibie]

He passed away, wow I didn't know that. I liked that guy, he used to pm me everytime I screwed up. Just watched a video online that symptoms were just like yours, was Abs pump. Theirs a way to reroute master cylinder bypassing pump to see if pedal gets hard. You might try that first. The pumps rarely fail, but your year is I think same if not close to the other members that did. Can't believe you've been driving with sinking pedal! When did Bob pass away?

Sent from my N9131 using Tapatalk

http://www.expeditionforum.com/threads/bedrck47-rip.35739/#post-303368

 

[Habbibie]

Also Moose please share that video I found couple the closest to my year I found was a 98 expedition and the guy just threw parts at it till it eventually got fixed

 

[stamp11127]

I'm 60+ and suffering from CRS and depression because of CRS...

I enjoy walking into Depot and the sweet little babe asks me if there is anything she can help me with. I look at her a say yea, do you remember what the hell I walked in here for?

 

[1955moose]

Stamp I'm same way. I can remember something I did in 1964, but can't remember something I heard yesterday.

Sent from my N9131 using Tapatalk