Bad Slave Cylinder?


Alex_Cie

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Last week, one morning I had no pressure in my clutch pedal. From my experience I immediately thought this meant a bad slave cylinder. Checked clutch master reservoir level and the fluid was low.

I bled the system to see if i could build pressure in the pedal. The first time I opened the bleeder valve a black liquid, and a bunch of air came out. I bled for a while until clear fluid was flowing out, and pressure actually built in the pedal to my surprise!

Started the truck up to see if the shifting was working. I could shift into first through fourth gear, but 5th and reverse were impossible to get into gear. My gear pattern seemed unusual and difficult to fully get into gears.

Seems like a transmission issue because if the clutch is working properly for the other gears, then the clutch should also work for 5th and reverse. Maybe I created some new problems by driving a few times (rev matching) with no clutch (and grinding the reverse gear a bit). Also, it could just be a cold weather thing because the truck as been sitting in 0 degree weather for a few days. I'm going to try heating up the transmission and seeing if the shifting improves.

I would really prefer to not drop the tranny this winter, so I'm hoping bleeding the system can build enough pressure to get me through the winter, with occasionally filling up the reservoir . But now I'm having this weird problem with my shifting. Would appreciate any thoughts.
 


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RonD

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Welcome to TRS :)

Nothing inside a slave to go bad, it can leak but its basically just a hollow cylinder that expands when you apply pressure to the hydraulic fluid inside it.

Not sure what the "black liquid" was maybe a seal is leaking and its sucking in air when you let up on the pedal, the air in the slave causes pedal travel issues, of course, but also the black liquid, oxygen is nasty stuff, very corrosive.

If pedal travel gets bad again and you get more air from slave when you bleed it again then slave does have a leak.
Can't really get air into the slave unless the reservoir runs dry and you pump the pedal, forcing air DOWN the hose, it would normally stay at the top.
So air only in the slave would mean its sucking it in, and most likely leaking a bit of fluid out


You are probably right, hard to blame clutch system if 1-4 shift OK
When did you last check the ATF level in the transmission, yes your M5OD-R1 manual trans uses ATF
I would check it and change it if its a darker red color.
Only holds 2.8quarts bone dry so not too expensive to drain and refill
 

Alex_Cie

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Thanks for the response. I've never checked the fluid before (I've owned the truck for 3 years), so maybe all along it has been leaking slowly.

I last changed the tranny fluid maybe 1-2 years (did use ATF), but i have noticed a small leak recently so maybe my fluid is low. I'll change it this weekend and see if that improves my shifting. It is a darker red color, so could be worth a change.
 

Shran

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Black liquid is most likely old fluid that is contaminated with the rubber boot inside the master cylinder reservoir. There is almost always at least some black crap floating around in the fluid when I take these apart... the boot/seal thing disintegrates over time.

Your shift issue is most likely related to air in the system from being too low on fluid. It can be bled out.

And yes you can keep an eye on the fluid level and top it off to keep the clutch functional for now, but how long it will last is anyone's guess. I was in a similar situation years ago and didn't have a shop to fix it in so I topped it off all winter and it was fine, maybe yours will be too, but I would just expect total failure sooner or later.
 

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Black liquid is most likely old fluid that is contaminated with the rubber boot inside the master cylinder reservoir. There is almost always at least some black crap floating around in the fluid when I take these apart... the boot/seal thing disintegrates over time.

Your shift issue is most likely related to air in the system from being too low on fluid. It can be bled out.

And yes you can keep an eye on the fluid level and top it off to keep the clutch functional for now, but how long it will last is anyone's guess. I was in a similar situation years ago and didn't have a shop to fix it in so I topped it off all winter and it was fine, maybe yours will be too, but I would just expect total failure sooner or later.
Thanks for the information. Would you suggest changing the clutch master cylinder then? I saw a video where a guy actually 'bled' the clutch master cylinder by maneuvering the piston. I may try this and see if there is some air in there. Here is the video for reference.

https://www.youtube.com/watch?v=Pd1KDCAhTLc
 

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That guy's method worked because it removed the weird angle in the master cylinder/firewall/hose arrangement. You could sure try it. Be aware that there is a plastic clip that holds the master cylinder pushrod onto the pedal and it is virtually impossible to get it off without breaking it.

I would plan on replacing the master cylinder and the slave cylinder at the same time - getting these things bled is enough work that you probably don't want to do it more than once.
 

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That guy's method worked because it removed the weird angle in the master cylinder/firewall/hose arrangement. You could sure try it. Be aware that there is a plastic clip that holds the master cylinder pushrod onto the pedal and it is virtually impossible to get it off without breaking it.

I would plan on replacing the master cylinder and the slave cylinder at the same time - getting these things bled is enough work that you probably don't want to do it more than once.
I agree with this statement, do both the master and slave, get prefilled if possible. make sure you only purchase a motorcraft slave cylinder I have heard that most others fail after 10-20k miles. and If it's been a while since your clutch was changed might as well do it too. If it's too cold to drop the trans just keep topping off the reservoir.
 

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I agree with this statement, do both the master and slave, get prefilled if possible. make sure you only purchase a motorcraft slave cylinder I have heard that most others fail after 10-20k miles. and If it's been a while since your clutch was changed might as well do it too. If it's too cold to drop the trans just keep topping off the reservoir.
I agree with what everyone is saying. Temperatures have been around -20F, even lower here in Wisconsin this week, so I really don't want to drop the trans right now.

I'm gonna try some more bleeding on the weekend and see if i can't get it back in commission.
 

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New Information

So today I began to disassemble the clutch master cylinder behind the clutch pedal inside the vehicle with the attempt of bleeding it like in a YouTube video previously shared.

Interestingly, when I pulled the push-rod and piston combo out of the master cylinder under the assumption fluid would start pouring out, nothing came out. From the looks of the push-rod piston.... well, there is no rubber piston. Now I'm not exactly sure what it is supposed to look like, but it appears the rubber has been completely corroded away. And this would explain initially why I saw black fluid coming out of the bleeder valve!
 

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It'll be a couple more days until I can dig through the trash for the one I just removed. But if I recall correctly, what you are looking at IS the Piston. The end with the black seal is what pushes the fluid.

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By the way. I would like to join the others and encourage you to replace both master and slave at the same time. Get a pre-filled system. The one I used is working flawlessly. I didn't have to bleed anything.

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Alex_Cie

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It'll be a couple more days until I can dig through the trash for the one I just removed. But if I recall correctly, what you are looking at IS the Piston. The end with the black seal is what pushes the fluid.

This message composed solely of recycled electrons. Go green!
I talked to a friend that works with brake systems for his job. He said typically on the piston there should also be a rubber seal on the top, which as seen in the photos would be missing in this case.

Tonight I got a new clutch master cylinder installed. Didn't feel like bleeding it, so I'll tackle that tomorrow and see if I get any promising results.
 

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I am going through similar issues. 97 Ranger, 220,000 miles, 2.3, five speed. I checked the fluids about a month ago and clutch reservoir was dry. Topped it up. Saturday went out to drive it and could tell the clutch pedal did not feel right. Topped it up, saw bubbles come up, then it worked great again.

I figured I need to replace the clutch master or slave or a hose, no big whoop, my first Ranger, but have done similar on plenty of other cars. So I look for parts. WTH, the thing uses an internal slave cylinder?

I am living with Sub-Zero temps too. Too cold to drop the tranny or even look for a leak. Hoping it is the master cylinder, for those with experience is one or the other more likely to fail? Still holding out hope.

Alex keep us posted, will be watching and hopefully learning, good luck.
 

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Most likely the slave. Keep an eye on the fluid level until it warms up or you can find a garage.
 


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