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Clutch not fully disengaging after HPDE...

AlbertD

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Background:
2016 Mustang GT with 29.5k miles. Frequently tracked in HPDEs every month with about 50+ 20 min sessions in the car's history.

At my last track outing... hit about 120mph in the straight and did my normal heel toe downshift from 5-4 to prepare for the upcoming turn, but after lifting my foot off the clutch pedal I noticed the clutch pedal did not return as fast as it normally does. I pulled it off track at that point as the pedal just didn't seem right. I also noticed it was now a lot harder to get it into any gear with the clutch fully depressed, but no grinding. The engagement point for the clutch is now at the floor making it extremely difficult to take off from a stop.

Diagnostics:
Inspected the transmission inspection hole and didn't notice anything out of the norm. Fluid level was fine, no apparent signs of leakage anywhere. I inspected the clutch pedal and didn't see anything that looked suspicious. The plastic connection on the rod that goes through the firewall that typically breaks on these cars was fully intact.

I suspected that I possibly blew some clutch material and lodged it into the pressure plate causing issue with disengagement. I do generate a good amount of heat on track and ring the car out to 7k quite consistently so it seemed plausible that the clutch material overheated and finally failed.

I pulled the transmission today to get a closer look. To my surprise, the only thing that looked out of the norm when removing the clutch assembly was the clutch disk had a slight mar with a crack through the disk material. The pressure plate also had a some slight marring, but... nothing that explains the clutch disengagement issue. The condition of the clutch looked OK. I'm still unsure at this point whether or not I will replace the clutch since if the problem persists I may very well mess up the new clutch by not properly breaking it in.

I'm quite confused at this point... the only other thing I can think of is perhaps I blew a seal in the master cylinder? The issue with that thought is the brakes work just fine and as far as I understood they work off the same system?

Anyone have any thoughts or experience similar symptoms?

My last resort is to take it to the dealership...

Pictures of the clutch -

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Well, it was likely just your clutch (brake) fluid got too hot. If it worked fine after some time to cool down, then that was your problem. As for that clutch, I would not want that back in my car for fear it would tear apart but it could very well be fine.
 
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AlbertD

AlbertD

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Well, it was likely just your clutch (brake) fluid got too hot. If it worked fine after some time to cool down, then that was your problem. As for that clutch, I would not want that back in my car for fear it would tear apart but it could very well be fine.
I was hoping that was the case, but the issue persisted after a 2 hour trip back home as well as in the morning after a cold start. I have the same thoughts about the clutch disk as well.
 
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AlbertD

AlbertD

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Hmm... I just measured the distance of each pressure plate finger (between tip of finger and ground) with my dial caliper and the disparity between them seems concerning. I'm wondering if this could be the cause of the problem...

in inches
2.526
2.530
2.522
2.560 max:2.560
2.460
2.486
2.474
2.492
2.457 min:2.457
2.470
2.475
2.485
2.498
2.504
2.510
2.519
2.523
2.490
 
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AlbertD

AlbertD

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Ordered up an Exedy Mach 500 clutch with their lightened steel flywheel, slave cylinder, and Steeda clutch line. Crossing my fingers...
 

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BmacIL

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I wouldn't expect that approx 10 thousandths across the range on the pressure plate to be the issue. Sounds like a bad TOB to me.
 
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AlbertD

AlbertD

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I wouldn't expect that approx 10 thousandths across the range on the pressure plate to be the issue. Sounds like a bad TOB to me.
Probably the TOB/slave cylinder. I lost mine at like 36.1k...
That could very well be it as well. I'm starting to wonder if I experienced vapor lock... I always bleed the brake calipers before every track event to ensure I am close to the dry boiling point spec for the Motorcraft fluid, but... I have never bled the clutch system. That fluid is the same fluid that has been in there since I bought the car and I'm assuming that fluid was fairly saturated and could have boiled.

I wish I would have tried vacuum bleeding the reservoir before pulling the transmission just to write off that possibility, but hey... live and learn.

I will be flushing the whole system with Castrol SRF and plan to vacuum bleed the clutch a couple of times a year so hopefully, this will not happen again.

Did you check that black clutch line connection on the left side of the master cylinder?

https://www.mustang6g.com/forums/showthread.php?t=84132
When I first bought the car, that was one of the first things I corrected. I pushed that line all the way back in and zip tied it. Has been snug ever since. It is also on my pre-track day checklist every month.
 

cop on my back

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This thread caught my eye. I am about to put a 4th clutch in mine, only about 25k miles on the car! First clutch blew on the road course at a high RPM shift, like many other factory clutches have on here. 2nd clutch was a McLeod RST and after one track day it was dragging, not fully disengaging. Took clutch out and sent it to McLeod, they replaced it with a new one under warranty. That clutch did one track day and it too is now dragging. Seems the heat from hard shifting warps the floating disc.

I now have the same clutch the OP has ready to install in his car, along with a lightened steel flywheel. Mine is not installed yet, too many other projects.

Not sure why yours was dragging, I also suspect the TOB started to fail. I know my TOB was new and the reason for the McLeod clutch failing was the heat warped the floating disc.

I hope the Exedy clutch will end my ongoing saga.
 

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AlbertD

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Jeez, sorry to hear that... sounds awfully frustrating. I get all the parts in this Monday so hopefully I will have it all buttoned up and ready to go by Monday night. I will report back with my results. My next track day is beginning of April so I plan to get those 500 miles of city driving in before then... ugh.

I am thinking it was the fluid that boiled as someone mentioned before, which potentially lead to the cascading failure of the rest of the system. Well... that is hopeful thinking...
 

BmacIL

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This thread caught my eye. I am about to put a 4th clutch in mine, only about 25k miles on the car! First clutch blew on the road course at a high RPM shift, like many other factory clutches have on here. 2nd clutch was a McLeod RST and after one track day it was dragging, not fully disengaging. Took clutch out and sent it to McLeod, they replaced it with a new one under warranty. That clutch did one track day and it too is now dragging. Seems the heat from hard shifting warps the floating disc.

I now have the same clutch the OP has ready to install in his car, along with a lightened steel flywheel. Mine is not installed yet, too many other projects.

Not sure why yours was dragging, I also suspect the TOB started to fail. I know my TOB was new and the reason for the McLeod clutch failing was the heat warped the floating disc.

I hope the Exedy clutch will end my ongoing saga.
Your driving seems exceptionally hard on clutches. One? Sure, defect. Two? Eh, bad luck but it can happen. Fourth one? It's you, buddy.
 

cop on my back

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I'm nearly 50, driven stick since I was 16. Ever road coursed, pushed a car hard? When you up shift hard on a track for 20 minutes things get hot. My 05 GT had no clutch issues on same road courses for years, so no, it is not me. Oh, and 4th one is not in car yet.
 

jasonstang

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Time for some steel clutch lines?
Could it be bad slave cylinder?
I had a Jeep would do exactly the same thing.
 

BmacIL

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I'm nearly 50, driven stick since I was 16. Ever road coursed, pushed a car hard? When you up shift hard on a track for 20 minutes things get hot. My 05 GT had no clutch issues on same road courses for years, so no, it is not me. Oh, and 4th one is not in car yet.
Yes I have.

Just to be clear, I don't think you're a bad driver, just the upper end of the design criteria. It's extremely odd for one person to have three separate, albeit similar failures and them not be a part of the problem. You might need something a little beefier to handle how you like to drive on track. Or, adjust your shifting to be less harsh on the clutch.
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