Mazda5 2.5L 6-speed MT: Clutch pedal feel/response changed suddenly while driving

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BMW M3 / Mazda5
After a few fast shifts today – not clutch dumps or anything, but upshifts in which I let off the clutch quickly – the clutch pedal suddenly started feeling like there was air in the hydraulic system. It was a bit inconsistent, but for the most part the engagement point was near the floor, and there was little to no feedback except spring pressure for the first ~3/4 of pedal travel.

177k miles on the vehicle. Clutch disc, pressure plate, throwout bearing, and pilot bearing are all basically new; hydraulics are all original AFAIK.

Any thoughts? I plan to try bleeding the system at some point (hopefully soon) but is there any other diagnostic work I should do?
 
So all clutch hardware was recently replaced? It is entirely possible that the new pressure plate cause either the master or slave cylinders to fail. I would try a fresh clutch hydraulic bleed, and see what that gets you. I would also be prepared to replace the slave or master, or both.
 
Clutch master looks like a significant job. Really hoping it's not that!

Is there a way this could have happened without the master or slave cyl failing? I do intend to bleed the system and see what happens, but if it's more likely that something has failed, I might just preemptively replace a thing or two while I'm under there, just to cut down on total time spent.
 
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If I were going to just throw something at it, it would be the slave cylinder. Shouldn't be too bad, and your plan was to bleed it anyway. Just make sure no air gets into the line up top.
 
If I were going to just throw something at it, it would be the slave cylinder. Shouldn't be too bad, and your plan was to bleed it anyway. Just make sure no air gets into the line up top.
Was thinking the same thing.

What I need to know is whether it's likely that a part has failed. If it is, I'll wait to bleed it until I can throw a slave cylinder at it. Otherwise, I'll try bleeding it sooner. Got a lot going on RN and need to be economical with my time/headspace. Does that make sense?
 
Was thinking the same thing.

What I need to know is whether it's likely that a part has failed. If it is, I'll wait to bleed it until I can throw a slave cylinder at it. Otherwise, I'll try bleeding it sooner. Got a lot going on RN and need to be economical with my time/headspace. Does that make sense?
Makes sense to me, as long as the car is still drivable.

For $80, maybe just have it on hand for when you get time:
 
Bled the clutch last night and put some miles on it today. Clutch feels normal and perfectly consistent. Whew!

No sign of leaks as far as I could tell. Fingers crossed!
 
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