Clutch pedal sticking to the floor when cold

[PCho222]

Hi guys, just posting this to document an issue I had with my clutch and what the fix ended up being since I haven't seen definitive threads/answers about my exact problem. Hopefully this can help somebody else someday.

Problem: Car was fine until one day I went to start it in the morning and the clutch pedal was hovering a few inches off the floor. I'd previously removed the pedal assist spring and so I could pull the pedal up with my foot and it would stay at the top, but have barely any resistance and stay if I pushed it back down. The first ~3/4 of pedal travel felt like air and pumping the pedal did nothing. The last 1/4 of travel had clutch pressure and I could get in/out of gear so I drove it. Five minutes down the road as the car warmed up, the pedal slowly started rising. A few more minutes later, the clutch felt normal again. The problem wouldn't repeat itself unless I let it sit overnight. This went on for a few weeks before I ended up fixing it.

Diagnosis: I never saw any drops of fluid under the car and nothing was wet underneath suggesting a leak. The brake fluid reservoir was filled to the max line and never fluctuated. My aftermarket clutch line was still tightly secured. I had no reason to believe air was in the line as it'd driven fine for a year until now. Most threads I read on M6G had physical leaks from either the clutch master or slave cylinder, thus identifying the culprit. In my case, I suspected there was an internal leak in the slave or master cylinder where the fluid was able to slowly leak behind the piston overnight until the fluid/cylinder warmed up enough to seal itself again.

Solution: I replaced the master cylinder (actually the whole pedal assembly since nobody stocked the cylinder at the time), pumped it a hundred times to bleed it, and it fixed it. Car's been driving fine for months ever since then. In my mind, it was a 50/50 shot between the master and slave cylinder being the cause. I chose the master cylinder off of a hunch. With the issues I've experienced over bad slave cylinders in cars and motorcycles, the problem's usually much less consistent, the clutch will feel all over the place, and the vehicle often tends to be undriveable. Also, there was no way in hell I wanted to get under the car and tear into the trans again, so there's that

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[Elp_jc]

Glad to hear your problem is over. And yes, with no leak, it HAS to be an internal one, and glad it was the easier of the 2 to fix . Hey, one question, since you apparently already tore into the tranny: How the heck do you bleed the slave cylinder? I only see one line going in, so the bleed valve is probably right on the slave cylinder itself, but want to make sure. Ford should have put a remove bleeder, to be able to easily do that from under the car, rather than having to remove the damn thing. Hope I never have problems with it .

 

[PCho222]

Glad to hear your problem is over. And yes, with no leak, it HAS to be an internal one, and glad it was the easier of the 2 to fix . Hey, one question, since you apparently already tore into the tranny: How the heck do you bleed the slave cylinder? I only see one line going in, so the bleed valve is probably right on the slave cylinder itself, but want to make sure. Ford should have put a remove bleeder, to be able to easily do that from under the car, rather than having to remove the damn thing. Hope I never have problems with it .

I don't ever remember having to bleed the slave or even the master. When we put in the new transmission a few years ago, I don't believe there were any nipples or bleed valves in there. We were told by the local performance shop that it's a "self-bleeding" system which sounded too good to be true but as a matter of fact, all I remember doing was pumping the clutch pedal a hundred or so times and getting one hell of a left-leg workout until resistance came back. Usually by the 2nd or 3rd day, the air is gone and it behaves normally. I agree it sounds wrong, but after having air in the clutch line of my bike and spending a week trying to get every last air bubble out with a cheap bleeder, I can appreciate the fact that the Mustang "figures itself out" without worrying about it.

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