Hi. I'm replacing my old transmission ('02 5MT in my wrx) with a newer transmission ('07 5MT from a 2.5RS). I'm having issues with the clutch system and was wondering what could possibly be going wrong with my clutch.
The problem is: Clutch pedal falls flat to the floor after about 60-100mi of driving losing all pressure. The problem occurs only when the engine is hot, occures mostly/more-often in city driving, and if the car sits for a while the pressure in the clutch pedal returns and all is functional again. So here's a list of what has been done.
1st - trans swap
'07 5MT from a 2.5RS
RS clutch kit
RS slave cylinder
Clutch Fluid, and bled the clutch system
The clutch failed about 60mi. down the road
But pressure in the clutch had been restored by the time i had the car returned to my garage.
I figured the slave cylinder wasnt drawing enough fluid to operate properly. So I replaced the master cylinder with a 2.5RS master cylinder in an attempt to patch up any compatibility issues in the hydraulic system. This now eliminated two problems which i figured could be occuring: an internal leak in the system, or a compatibility issue between the hydraulic components in the clutch.
The clutch failed 100mi. down the road, leading to my second fix.
At this point im completely confused. I figured an incorrect master cylinder was sent to me. So I replaced the master again. I also noticed there was no return spring present on the '07 transmission. So i fabricated a bracket and installed a return spring. And finally, I made sure to bleed the system longer than i would ever consider neccessary making sure all air was completely gone.
The clutch this time failed 120mi. down the road.
So here i am now. I figure the only thing left is the clutch hose, so I'll be replacing all the lines. Maybe there's a pinhole leak that formed while i was performing the swap or replacing parts. I cant figure out what could possibly be the cause of the problem. The clutch works, and sometimes it dosnt. Any help would be greatly appreciated.