Help diagnosing clutch non-release?

[86league]

Hi.


My 2020 BRZ fairly suddenly got to where the clutch is not releasing and the trans input shaft is always spinning with the engine. Clutch-in cranking moves the vehicle if it's in gear. Shifts fine into all gears with the engine off, but cannot select any gear with the engine running even with the clutch in.


Noticed it was hard to shift into gears so I left it in 4th until I could get to where I could take a look. Swapped fluid and bled the clutch slave - no air. Next drive it would shift sort of OK at low RPM, but if I revved up I couldn't really even get it into neutral unless I got it to exactly the right amount of throttle to not be accelerating or engine braking.


Bled the clutch again (still no air) and then it got to where I couldn't get into any gear at all.



Want to eliminate the hydraulic system (master/slave cyls) and/or do any other troubleshooting before I am forced to pull the trans.


- The slave cylinder is moving (extends a little over 1/2" from pedal up to down. -- Is there a spec for how far it should travel with full clutch pedal press? I didn't see it in the service manual.


- Slave cylinder can be depressed/retracted by hand and then extends until it touches the fork. So, it seems the self-compensation is working. The clutch pedal seems to be adjusted to spec (values from the service manual)



- My cheap borescope does show that the TOB/clutch fork move when the clutch is pressed, and the pressure plate fingers are flexing. Hard to see much in there but it does look like the pressure plate itself is moving aft as the fingers flex. I didn't see any obvious signs of trouble or broken/bent parts.



- Tried to look to see if the fork was bent looking down from the top, but I can't tell.


- On the lift I can start the car in gear and rev it up - it acts like the clutch pedal is up even when down - the engine is not free-wheeling, it has to accelerate the driveshaft/tires. Stepping on the brakes with the clutch in with some speed of the rear wheels results in some bad sounds from the clutch (or clutch area). So, it does slip but it doesn't sound happy - not like a slight slip you would do starting out in first.


- What else can I do before pulling the trans? Like to verify the slave/master cyls are within spec but I can't find a spec for the slave stroke length.


Thanks for any/all help!

[86league]

Well - I have my answer.


Clutch disk failed - damper springs worked sideways and jammed against the pressure plate springs while holding the disk against the flywheel.

[Tokay444]

Yep.