weird brake issue 97 xlt

[IMINYOURCHAIR]

97 xlt 278k new pads/rotors all around. brake fluid is where it should be and clean. system has remained sealed since I purchased four mos ago.

issue: brake pedal threshold is random. where it used to begin to slow about 1/5 way down it now goes about1/2 way down for the same effect. the braking is un effected and she stops as she should the pedal just has a larger dead zone but randomly it acts normal. a visual revealed no suspected leaks, all teh bleeder valves are dry as are the hoses calipers etc..

 

[IMINYOURCHAIR]

Issue still persists, going to bleed brakes tomorrow and pull all four calipers to grease the slide pins.

 

[IMINYOURCHAIR]

okay, I bled all four wheels, did each three times. absolutely no air came out...i did however notice that when off, the pedal will still slowly sink to the floor when steady pressure is applied but not at each press, sometimes it'll hold, then it'll go half way and if you back off slightly then re apply pressure it'll sink the rest of the way in. while this is happening there seems to be fluid moving around the reservoir.

the system is sealed all around from what I have observed and has been for the 5000 miles I've driven since November.

 

[High Desert]

Any sign of leaks around the master cylinder? The slowly sinking pedal under pressure could indicate the master is getting weak and bypassing internally.
Good luck on it.


Shaun

 

[IMINYOURCHAIR]

I am going with it bypassing internally. there is absolutely zero fluid going anywhere outside the system. I've checked and double checked every part of visible line from the master to the abs back to each wheel. the thing is, it'll stop reliably each time. it's just where the brakes engage at relative to pedal travel changes. sometimes it's firm as usual, sometimes it'll engage about 15% deeper then when that happens if i back off of it even slightly it will re engage another 15/25% of travel (about 50% of pedal use at that point.) then it'll finally have usable stopping power at 75-80% pedal travel used. then, i can return the pedal to 0% and try again and it may go 1/2 to 3/4 before catching or it may go 1/5 before catching.

I can do the same thing when the engine is cut off too. booster hose is clean too (inside/out)