What would be the most likely cause of the clutch pedal suddenly losing resistance?


alwaysFlOoReD

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You made sure the rubber diaphragm wasn't sucked into the master?
Yeah, that's what I did. No change in pressure, very little fluid movement down/out. Dead MC right? If it was the slave would it feel different? I imagine you wouldn't be able to tell.
 


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Josh B

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Haha, sorry to laugh but that would a really big blob going down that line, haha, sorry still laughing, I never woulda thought it
 

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I know there's a lot of pressure produced by that master cylinder, and rubber lines will expand and diaphrams will compress, as well as fluid will not, but I really just never woulda thought about that one either.

Must have looked like a snake had swallowed an egg if you had seen it
 
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alwaysFlOoReD

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No it doesn't go down the line. Vacuum sucks onto and down the walls of the master so it looks like its a part of the master. If you don't know about the diaphragm (like I didn't) you would just full it up with fluid and wonder why there was no fluid getting to the slave....
Kind of like a vaginal condom.
 

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You made sure the rubber diaphragm wasn't sucked into the master?
Ah hah! I remember you saying something about that but not quite understanding it was what I was looking at. Okay. I'll see what happens now. Thanks...
 

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alwaysFlOoReD

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That diaphragm is supposed to be squished accordion-like into the cap when everything is working correct. As fluid is lost it extends down into the master. This is to keep oxygen from contacting the clutch fluid.
 

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Now how on earth do you get the push rod off the end of the pedal linkage there? Again the book says just work it off. I need a tip or two before I break something. I was lucky enough to get that fuel plug off the tranny without a special tool without breaking anything. Don't want to push my luck. Anyone remember how they did this one or just in general how to remove these? The little black cage there grips the piece on the pedal like a nipple on four points into a groove. What's the trick?

And yeah, no luck after removing diaphragm. So fingers crossed the MC is the issue. I don't see how it would be anything else at this point
 

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Josh B

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They lock in, it won't come out, hence the brake booster, take it off and you can turn it upwards and get it out.
Did you get a master cylinder? Look very closely at the instructions, it will give a warning to most Ford applications, along with an 800 number. Call that number, and after you talk to them I'll tell you the gory details ;)
 

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Ahh, the little clip thing. Looks like you need some long nose pliers to squeeze the tabs, then pop it out with a screwdriver

Sorry, I overlooked the photo and jumped right into the moat :D
 

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No no, nothing special. Just stick a screw driver in and pop it off. Thank God.
 

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So how do you test this thing out? I'm about to fill it with fluid and see if I can make it rise to the top of the reservoir. Pressing the rod is got good spring resistance. I just want to check whatever I can before I install this $60 part

I'm kinda lost at this point. I was expecting it not to depress with such resistance. I thought it would be loose if there wasnt a leak or failure in the slave. Should I have bled longer? I'm assuming bleeding should immediately almost move the fluid either to the reservoir or out a leak point but nothing happened when I tried.
 

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That was probably a dumb presumption on my part. Of course there will be tight spring action from the rod. I'm just holding out now before I pop this new part in. Any ideas on anything I could look for to determine the likelyhood(is that a word?) the MC is faulty? I've just got this fear it will turn out to be the slave in which case I'm selling this truck with a new extra MC I just paid for.

Edit: Guys help me understand this: if it was the slave, I'd still be able to get pressure built up in the system no? And this soft peddleness should be due to fluid slipping past the cylinder inside this MC right(since no external leak)? This assumption is correct? Gonna take some time and research more. If no other ideas on this I'll just cross my fingers and pop in this new MC tonight

Edit: apparently people have had problems bleeding the MC. This guy:


had a soft pedal problem he fixed by fully decompressing the MC piston my releasing it removing the c-clip as that somehow let fluid go all the way in there whereas air had apparently been stuck in there despite bleeding attempts and that proper bleeding fixed his issue, so that might be what I got going on. I'll look into it more and probably end up trying to bench bleed it and reinstalling it. Saw some vids on bleeding this truck. I guess it's a little trickier than other vehicles...

This mechanic right here explains it clearly about the bad angle the MC is installed and how he bled it similarly to the other guy in the other vid.


... if anyone's interested following this thread. I've got a good feeling this is what I'm dealing with and I'll be able to return this MC.

And yet again!


Another creative bleeding solution. Or is it? He uses an auto bleeder (which I have in my garage somewhere) and sticks it straight into the reservoir with a little skinny cone adapter which I guess is strong enough to force the air out of the MC. Well this is good news. I'll take my whole removed system home and bench bleed it with my auto bleeder then bring it back out here tomorrow. Hope this is the answer...
 
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Josh B

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On mine I had to also pull the line going on down to the transmission, gravity bleed them while together and twisting it all around to work the air to the top. Then close the reservoir and install it as a unit
 

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On mine I had to also pull the line going on down to the transmission, gravity bleed them while together and twisting it all around to work the air to the top. Then close the reservoir and install it as a unit
Gravity bleed? Work it around to the top?

First of all, when you normally bleed a system, does the air travel faster than the fluid at all or do you just gotta have the air basically wait in line to exit?

Before googling I'm guessing gravity bleeding is letting gravity pull the fluid to the bottom and the air rising to the top, reservoir in this case right? No, then everyone would do that.... Oh, bubbles get stuck where the lines do a turn like what your sinks do underneath. I think I get it. Wait, so as long as it's some inclined with no up turns it bleeds on it's own?
 

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There are twists and turns and little nooks and cranny's in mine that just don't seem to be bleed-able short of pulling the complete line out, hanging the entire set-up high enough it doesn't touch the ground, and constantly filling the reservoir while wriggling all the parts and hoses around to allow all the air to escape. Then close it up and install it as one complete unit from the reservoir to the slave attachment, then simply gravity bleeding the slave cylinder.

I'm not sure if yours is the same. Look in the instructions that came with your MC very closely, somewhere in there should be a note to Ford applications about calling their 800 number for information on bleeding the system. If not, maybe they've corrected it, but if you're having problems I'd think it hasn't been addressed, and you should get their info specifically to those models.

They knew about it in 2006 the first time I did mine, but I found out very late in the game. I had begun with parts store parts, and maybe a bit from Ford. Early in my ordeal a Ford parts clerk had run into numbers that he couldn't understand. Later in that project I was again at Ford dealership and being helped by their parts manager. He understood what was going on, but I was too far along at that late date to change courses.

They had a newer system even for my vehicle that addressed the difficult bleeding problems, but it required using only the newer systems parts thru the entire process, they were not interchangeable.
I did mine again maybe 6 months ago, and all the parts I got readily worked on my system, so I suppose if I'd had the newer system, all Ford parts would have been my only option.
 


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