Mushy clutch pedal and strange noise after 4k RPM's

[hxt_BRZ]

So I recently did some work on my car:
ACT XT Street clutch w/ Street-light flywheel
Verus Engineering Clutch Fork
Verus Engineering Clutch fork Pivot

Followed all instructions in the DIY clutch replacement thread to the tea. Still after about 4k and above RPM, no matter the gear I'm getting this grinding/rubbing noise, not really sure how to describe it, video is linked below with audio.

Video:

Symptoms:
- Audible grinding noise coming from the footwell
- Clutch pedal has no pressure first half of travel, only starts to feel normal at about 3/4 depression

Car still shifts smooth, no issues there. Noise and pedal feel only occur after 4k rpm and sometimes doesn't start until higher (4.5-5k).

[humfrz]

Originally Posted by hxt_BRZ

So I recently did some work on my car:
ACT XT Street clutch w/ Street-light flywheel
Verus Engineering Clutch Fork
Verus Engineering Clutch fork Pivot

Followed all instructions in the DIY clutch replacement thread to the tea. Still after about 4k and above RPM, no matter the gear I'm getting this grinding/rubbing noise, not really sure how to describe it, video is linked below with audio.

Video:

Symptoms:
- Audible grinding noise coming from the footwell
- Clutch pedal has no pressure first half of travel, only starts to feel normal at about 3/4 depression

Car still shifts smooth, no issues there. Noise and pedal feel only occur after 4k rpm and sometimes doesn't start until higher (4.5-5k).

Welcome to the forum, there hxt_BRZ -

So, you did the clutch work yourself? If not, I'd suggest you take it back to whoever did it.

You did replace the TOB - right?

If you did the clutch work yourself, I'd suggest you bleed the clutch system (again) and if that don't hep it, adjust the clutch.

That's all I got.

I'm going to refer you to our clutch expert, ol @Ultramaroon , just to piss him off for bugging him on his day off -

I hope you get it sorted out.


humfrz

[hxt_BRZ]

Yeah, everything in the clutch system was changed out, TOB included and I did do the work myself.

I'll try bleeding the clutch and see if that helps

[Ultramaroon]

If it works normally at low engine speed, I suspect something is causing knock-back at the TOB. If you drive it through the high rpm and then slow down the engine for a few seconds before pressing the clutch, does it recover on its own?

[humfrz]

Originally Posted by Ultramaroon

If it works normally at low engine speed, I suspect something is causing knock-back at the TOB. If you drive it through the high rpm and then slow down the engine for a few seconds before pressing the clutch, does it recover on its own?

"knock back", what the hell is knock back? Or, did you jest make that up? -




humfrz

[Ultramaroon]

*sigh* Go pull forward on your clutch fork. Now get in right away and push the pedal. Don't ask dumb questions. Just do it.

[RZNT4R]

Well since you've got a grinding noise it'll be easy enough to check your work for the self-clearancing marks making the issue evident!

[hxt_BRZ]

@Ultramaroon , that's exactly what happens, when the RPM's drop back down the clutch pedal recovers on its own and the sound goes away. I took it for a drive down an empty road earlier and tested with multiple conditions. Noise and mushy pedal occurs between 4-5k. What would be the best course of action to address the knock back? and do you think it could be caused by a weak retention spring on the clutch fork?

[Ultramaroon]

Originally Posted by hxt_BRZ

@Ultramaroon , that's exactly what happens, when the RPM's drop back down the clutch pedal recovers on its own and the sound goes away. I took it for a drive down an empty road earlier and tested with multiple conditions. Noise and mushy pedal occurs between 4-5k. What would be the best course of action to address the knock back? and do you think it could be caused by a weak retention spring on the clutch fork?

I could be wrong but I don't think it's clips or a retention spring. I think something is loose in the pressure plate and the centrifugal force at that RPM is pushing out of whack something involving the pressure plate fingers.

Try reinstalling only the stock pressure plate and see if that eliminates the vibration and mushiness.

[humfrz]

Originally Posted by Ultramaroon

*sigh* Go pull forward on your clutch fork. Now get in right away and push the pedal. Don't ask dumb questions. Just do it.

OK, old man, I googled "knock-back", this is what I found -

Now, quit ah messen wich me -


humfrz

[hxt_BRZ]

Alright well, I started with the easy stuff (bleed and adjust) to no avail, problem still persists so I'll most likely be attempting to drop the transmission whenever I get a chance this week and let y'all know what I find

[Ultramaroon]

Good luck.

[RZNT4R]

BTW, there's a roll pin locating the crank position sensor reluctor ring on the crank, people have been known to reinstall the flywheel in the wrong position, crushing that pin, which makes the flywheel sit crooked on the crank.

Remove the access cover on the right side of the block opposite the crank sensor, and as the engine runs, looks for a wobbly flywheel. Hint: It should run PERFECTLY true.

That's easy enough to check without tearing into everything, though if it's not straight, you'll have to tear into everything .