Hey guys so today my clutch started slipping, my wife was driving it and she described a problem that sounded like a badly slipping clutch from her description but the clutch has been just fine every time I’ve driven it this week so i figured theres no way my clutch died all of a sudden with zero indication of it starting to go. Well she gets home, i jump in the car and the clutch has pretty much zero pressure and i had to rev the hell out of it just to catch reverse. Its dark now and i don’t know enough about this to feel confident if its a bad clutch or if its like a slave cylinder or something like that because it was just fine yesterday and all of a sudden my pressure is absent. So does this sound like a dead clutch or something less dire like the slave or a busted hose? Thanks for any kind of input or suggestions in advance everyone. Forgot this but we’re dealing with an 04 mazda 6 2.4L 187k miles
The “no pressure” comment leads me to think it is a master or slave cylinder issue. You could have checked this yourself very easily by checking the fluid level on the clutch master’s reservoir. If the fluid is low, there is a leak and it likely the slave.
Go check. Report back, please.
It sounds like the slave cylinder is leaking and the clutch plates are contaminated with hydraulic fluid. That would explain the slipping clutch and the lack of pedal resistance. If my own similar experience with an old Corolla is any guide, you need both a slave cylinder and a new clutch.
Assuming the car in question has a hydraulic clutch. (Rather than cable activated.) If the hydraulics are leaking, shifting from one gear to another with pedal depressed and engine running will be difficult, may involve grinding noises. Is that happening? If so, does pumping the pedal a few times before shifting seem to help?
If the clutch disc itself is worn out and slipping, hydraulics working ok, shifting gear to gear won’t be a problem. The symptom for that, when driving in gear, in certain situations the engine rpm increases but the car speed doesn’t. Usually most noticed in the higher gears, 3,4,5.
If the slave is located inside the bell housing I supposed both problems could occur as mentioned above, slave leaks, fluid contaminates clutch disc which causes it to slip. My guess, this isn’t your problem. Slave cylinder very simple gadget, hydraulic problems w/slave much less common than problems w/clutch master cylinder.
How can that happen if the slave cylinder is mounted outside the bell housing? 
Tester
Good question. In the case of my old Corolla, the seal between the clutch and transmission was bad and the clutch had been contaminated with oil. It seemed like a reasonable possibility that the same thing could happen if the slave cylinder were leaking.
Someone got the clutch so hot it took the temper out of the diaphragm spring in the pressure plate. Clutch is destroyed. Try to forgive.
On my Corolla the slave is located outside the bell-housing, so if it leaked the fluid would drip on the ground, couldn’t get on the clutch disk which is inside the bell-housing. Newer cars, the slave is often inside the bell-housing.