hey everyone, hope you are doing fine as i am slowly going crazy. my truck is an 08 4.0 5 speed sport. i got it in 2015 and around late 2016 i had the master and slave cylinder's replaced as well as the new clutch/pressure plate. ever since then my truck has had 3 masters and 4 slaves in and out of it because the clutch is either not completely bled upon getting it back and WONT completely bleed or will keep good pressure for a couple of weeks, then the pedal slowly starts to loose pressure and clutch will start to engage closer to the floor. we just replaced lines a couple months ago. the entire clutch system, from the rod to the pressure plate, is under 5 months old and im at square one. i started with my local garage but moved on to a ford dealership last year in hopes they knew what they were doing, but they can't figure out wtf is wrong. they even called in "ford specialists", all they suggest is throwing another slave in....
i know the system has a gremlin but i can not be the only one battling this pos. i love this truck, i never planned on getting rid of it but ive had autotrader open more than i'd like to admit. this truck is perfect minus this. most of the work done has been under warranty, however im still thousands of dollars deep into trying to fix this.
thanks guys any help is appreciated.

p.s. only diy fix i tried is sucking the air out from the reservoir, both with my mouth and a vacuum tool. both did nothing.

 

I know this doesn't help, but I have also been through 5 or so slave cylinders since 2014. They last for a little while and then they fail.

I just recently had the same issue as you are currently having. I replaced my third slave a year or two ago, because it was leaking fluid externally. Not long after, the 4th one that I put in as a replacement seemed to be taking in air every two weeks after bleeding it. I didn't want to pull the transmission AGAIN, so for almost a year I just left the inner fender out of the truck so I could remove the master every two weeks to bleed it. Last month I purchased a slave cylinder directly from Ford and threw it in. So far, it has fixed my issue and I no longer have to keep bleeding the clutch. We will see how long this one lasts.

The reason you're having this issue is because there are only two or three companies making slave cylinders for these trucks. They are all making an inferior product and every time you buy one, you are taking a chance on whether it will work or not. You may get lucky, or you may go through three before you find one that lasts awhile. It's just the unfortunate truth. I've been holding out hope that one of the reputable clutch companies would offer a high-quality slave cylinder for our trucks, but so far that has not happened and likely won't.

 

i was ready to accept the fact that it's just not a well made part lmao this does bring a little peace to mind though. after reading this i realized i never checked this slave and its all dry in there so i guess its just air getting in the system.
at this point ill just go back for warranty repairs, until then, when you were bleeding every two weeks how would you do it? bench bleed? trying to avoid that but sounds better than pumping the literal life out of my clutch for pressure at this point. thank you for your input

 

Mine was dry as well, with no visible signs of failure. I just guess it was machined poorly and that's why it leaked.

As for bleeding, I was removing the master cylinder and line from the truck and bench bleeding it utilizing the process outlined by Perfection Clutch on Youtube. Thats always worked to get the bubbles out and the clutch was fine for about two weeks but by the 14th day I was back down to the floor. I guess it's better than the slave cylinder just leaking all of your fluid, but it was still annoying having to bleed the clutch so often.