Clutch pedal sticking down, still engaging

[Troph]

Update: It's now been 3 whole driving days since the flush procedure, and the clutch is still working... i.e., it hasn't gotten stuck yet! I'm obviously happy. I'm hoping the entire problem was just due to some air getting into the clutch line. Now that I think about it, I did notice a few months ago that the reservoir didn't seem to have any fluid, so I added some (it didn't take much at all). But maybe it had gotten just low enough to suck some air into the clutch master cylinder? (Which begs the question of where the fluid went...)

It's still absolutely possible of course that the issue is inside the slave cylinder, and the process of flushing fluid past it has just temporarily restored its function. If the symptoms ever return I'll post again.

But if this has taught me anything, it's that I need to be more diligent about flushing and checking these hydraulic systems regularly, because there was certainly no indication that anything was wrong until the pedal started misbehaving.

 

[TDavis]

Update: It's now been 3 whole driving days since the flush procedure, and the clutch is still working... i.e., it hasn't gotten stuck yet! I'm obviously happy. I'm hoping the entire problem was just due to some air getting into the clutch line. Now that I think about it, I did notice a few months ago that the reservoir didn't seem to have any fluid, so I added some (it didn't take much at all). But maybe it had gotten just low enough to suck some air into the clutch master cylinder? (Which begs the question of where the fluid went...)

It's still absolutely possible of course that the issue is inside the slave cylinder, and the process of flushing fluid past it has just temporarily restored its function. If the symptoms ever return I'll post again.

But if this has taught me anything, it's that I need to be more diligent about flushing and checking these hydraulic systems regularly, because there was certainly no indication that anything was wrong until the pedal started misbehaving.

This, literally this lol. This is me

Mine is going good so far after flushing and its been a couple weeks now. The dirtiest fluid came out of the slave compared to the calipers

 

[Intuit]

Good feedback. The design of the reservoir makes it extremely hard if not impossible to monitor levels. If this is like my prior Ford, the clutch and brake are separated by spillway and the clutch is but a tiny back corner of the reservoir. The only time my clutch fluid got low was when the master cylinder started leaking at the firewall. The slave was external to the transmission; on the bell housing. If the slave ever leaks on the FiST, we'll never see it. It is possible for a seal to leak in such a way that it "sucks" air back into the system as the piston retracts.

 

[TDavis]

Good feedback. The design of the reservoir makes it extremely hard if not impossible to monitor levels. If this is like my prior Ford, the clutch and brake are separated by spillway and the clutch is but a tiny back corner of the reservoir. The only time my clutch fluid got low was when the master cylinder started leaking at the firewall. The slave was external to the transmission; on the bell housing. If the slave ever leaks on the FiST, we'll never see it. It is possible for a seal to leak in such a way that it "sucks" air back into the system as the piston retracts.

Yeah Fords design for the FiST is weird since you have an off shore reservoir that you use to fill that goes to another reservoir since you're unable to get to that one.

Also, if the slave is leaking enough it'll drip onto the ground since it'll be coming through the mating surface of the bellhousing and engine block

 

[M-Sport fan]

If a shop or dealer is going to do a pressure flush of the clutch hydraulic system (versus a gravity flush/bleed), they would attach the cap/fitting to the main reservoir, correct??

Since the secondary, CLUTCH master cylinder one does not have it's own cap, correct?

Or is no external pressure supposed to be put on the clutch master/slave cylinders, and only the hydraulic pressure of pumping the pedal supposed to be used?

I so wish that we had a remote, check valve at the end, clutch bleeding hose available to us like the Tremec T56/TR6060 crew has for their setups.

Fully under hood bleeding/flushing, with no jacking up, or getting under the car, AT ALL, and ONE person can do it easily.

 

[Troph]

I don't know what the official Ford procedure is; maybe someone else can chime in about that. I would assume they have a pressurized bleeding system and don't resort to the old-fashioned two-mechanics approach?

I used the pressure bleeding system mentioned above, which attaches to the main reservoir and uses about 12-15psi only. I found this technique to work very well, as I was able to do the entire thing myself, and as soon as I was finished, the pedals were nice and firm. No pumping, no repeat bleeding, etc. I would imagine this amount of pressure coming in from the reservoir past the master cylinders is relatively safe.

Because the brakes and clutch share a reservoir in this vehicle, IMO it only makes sense to flush both at the same time, which would involve having access to the caliper bleed valves no matter what.

It's my understanding that dealerships and advanced shops will have a computer interface which can additionally instruct the ABS pumps to operate during the flush procedure, which will flush out those systems much better than either the 15psi pressure-bleed or gravity-bleed approaches would do. Personally, I was not too concerned about leaving that small amount of older fluid behind.

 

[TDavis]

I don't know what the official Ford procedure is; maybe someone else can chime in about that. I would assume they have a pressurized bleeding system and don't resort to the old-fashioned two-mechanics approach?

I used the pressure bleeding system mentioned above, which attaches to the main reservoir and uses about 12-15psi only. I found this technique to work very well, as I was able to do the entire thing myself, and as soon as I was finished, the pedals were nice and firm. No pumping, no repeat bleeding, etc. I would imagine this amount of pressure coming in from the reservoir past the master cylinders is relatively safe.

Because the brakes and clutch share a reservoir in this vehicle, IMO it only makes sense to flush both at the same time, which would involve having access to the caliper bleed valves no matter what.

It's my understanding that dealerships and advanced shops will have a computer interface which can additionally instruct the ABS pumps to operate during the flush procedure, which will flush out those systems much better than either the 15psi pressure-bleed or gravity-bleed approaches would do. Personally, I was not too concerned about leaving that small amount of older fluid behind.

Fords procedure is to reverse bleed it from the slave bleeder. Which to me means push fluid through?

 

[TyphoonFiST]

Fords procedure is to reverse bleed it from the slave bleeder. Which to me means push fluid through?

Correct*

 

[Intuit]

Ordinarily I never top-off because when you replace the brake pads the fluid just gets pushed back out. This past weekend (checking the brake pads) I went ahead and topped-off the reservoir. Took very little fluid to bring it back into view, despite well worn pads that don't yet require replacement.

Haven't had any issues... but it's easy/cheap insurance.

 

[Troph]

Update: After about 45 days, this problem has returned, unfortunately. I was just taking off from a red light yesterday, and after taking off in 1st gear, the pedal didn't pop back out. So in my case, bleeding the system made the symptoms totally disappear for over a month. When I checked the fluid reservoir, it appeared to be full. Similarly, the bottom of the transmission still appears dry, so I don't see any evidence of a leak. Nevertheless, I'm reasonably sure that the issue is the slave cylinder as everyone was warning.

Since that involves paying a shop to drop the transmission (which is beyond my willingness to tackle), I figure I might as well pay them to put in a new clutch too... and maybe even an MFactory LSD swap? At least that way, all the money I'm spending will feel like an upgrade rather than just evaporating...

 

[SteveS]

If you're paying to have the transmission out, definitely doing the clutch makes sense. The LSD you're getting to piggyback without paying the labor twice.

 

[our guile]

I replaced both the clutch and flywheel based on the shop's recommendation. The flywheel might be a little over the top but there's no reason not to replace the clutch while the transmission is out anyway.

And I highly recommend the MFactory LSD. It's been an amazing mod.

 

[Intuit]

Update: After about 45 days, this problem has returned, unfortunately. I was just taking off from a red light yesterday, and after taking off in 1st gear, the pedal didn't pop back out. So in my case, bleeding the system made the symptoms totally disappear for over a month. When I checked the fluid reservoir, it appeared to be full. Similarly, the bottom of the transmission still appears dry, so I don't see any evidence of a leak. Nevertheless, I'm reasonably sure that the issue is the slave cylinder as everyone was warning.

Since that involves paying a shop to drop the transmission (which is beyond my willingness to tackle), I figure I might as well pay them to put in a new clutch too... and maybe even an MFactory LSD swap? At least that way, all the money I'm spending will feel like an upgrade rather than just evaporating...

Fluid is much more dense than air. It's possible that the seal on the slave is not leaking fluid out, but air in, as the fluid behind the piston retracts. Had a cooling system with a cracked radiator that for a time, found it easier to suck in air, over pushing out fluid. The caliper bleed screw seats on the prior motorcycle just about drove me batty trying to figure out what the hell was going on... https://www.r6-forum.com/threads/resolved-brake-bleed-screws-wont-seal-leak.444882/

 

[M-Sport fan]

Update: After about 45 days, this problem has returned, unfortunately. I was just taking off from a red light yesterday, and after taking off in 1st gear, the pedal didn't pop back out. So in my case, bleeding the system made the symptoms totally disappear for over a month. When I checked the fluid reservoir, it appeared to be full. Similarly, the bottom of the transmission still appears dry, so I don't see any evidence of a leak. Nevertheless, I'm reasonably sure that the issue is the slave cylinder as everyone was warning.

Since that involves paying a shop to drop the transmission (which is beyond my willingness to tackle), I figure I might as well pay them to put in a new clutch too... and maybe even an MFactory LSD swap? At least that way, all the money I'm spending will feel like an upgrade rather than just evaporating...

Has it been very hot there for the past month?

 

[Troph]

Has it been very hot there for the past month?

Actually, it was much warmer here when I first bled the system in September, and prior to that, it had been a particularly hot summer when it was acting up. However, when it acted up again for the first time this week, it was a "cool" morning (for central FL) around 65 degrees... down from the 90+ days in September. And I had only driven the car for maybe 5 minutes up to that point, so I don't think the fluid was particularly hot either, but of course it's hard to know.

My dad had a 2005 Altima SE-R with a manual transmission, and back in like 2010 that thing had a different clutch issue where in the dead of summer and after driving in heavy traffic (i.e., the hottest possible conditions, worst possible cooling), the clutch would lose pressure and sink all the way to the floor. Flushing the system didn't seem to help. The only workaround was to pull over, turn off the car for a few minutes, and then when you restarted it, everything would be fine. So based on the symptoms, it was pretty clear it was heat-related. None of the shops could help, but eventually after some forum research, I learned that car had a poor hydraulic line design where the clutch line was routed right past the exhaust manifold, and there was no heat shield separating the two. So the heat would eventually start boiling the fluid, hence no clutch pressure. The fix was to add shielding on the line and make sure to use proper DOT4 fluid, and it never happened again.

Unlike that case, my Fiesta clutch issues don't seem to be related to heat soak or ambient temperatures. But it is true that this hot summer is when the clutch was misbehaving the most.

 

[Troph]

This morning it stuck multiple times on my way to a doctor's appointment. When I got back home, I ordered a new master cylinder, slave cylinder, clutch, axle seals, MFactory LSD, and a LSD install kit from Whoosh. Working on finding a good local transmission shop.

 

[fST]

I think I may have posted in this thread earlier so just as an update, or a datapoint if I haven't posted here.

I had this issue and it was getting progressively worse up until the end of last summer (noticed it only happened when it was very hot/humid outside) when I had this brake issue where I ended up needing new brakes as well as some brake sensor/module replaced (can't remember the exact name of it). The shop had to do a complete brake/clutch fluid flush.

Since I got the car back from the shop when that work was done, I have not had a single instance of the clutch pedal sticking to the floor. I went through the entire summer with no issues. It's now been just over 1 year.

I had spent last winter researching and calling shops to have the clutch, master cylinder, slave, replaced, plus a LSD installed at the same time. Luckily I decided to wait for the issue to pop up again (I expected it to do so when it started getting hot this past summer). I'm glad I decided to wait. I would like an LSD though lol

 

[M-Sport fan]

^^^Which brake fluid did you use for that full flush of the systems?

 

[fST]

^^^Which brake fluid did you use for that full flush of the systems?

I had it done at a local Ford dealership so I assume they just used Motorcraft fluid. I'm not sure if the paperwork would have that detail or not. I could check it when I get home, if I can remember to do so.

Also, I just remembered that what failed was the ABS control module on the passenger front wheel. They told me due to that, they had to do a complete brake fluid flush of the entire system, more than a regular brake fluid flush. I don't know if that's true or if that makes sense but that's what I understood of what the Service Advisor told me.