My son has a 1993 F150 4.9 5 Speed. Randomly the clutch pedal collapses to the floor and fails to disengage fully. It has to be pulled back up and then functions perfectly until the next time it randomly sticks/collapses ... It is a hydraulic clutch and full of fluid. I did notice that the rubber diaphragm inside the master cylinder is extremely swollen. I know this is typical of having the wrong fluid put in the system ... not sure what I should do now ... any suggestions? Clutch feels great and functions perfect 90% of the time?

Thanks for any input/advise!

 

First thing is to carefully check for fluid leaks in the hyrdo system.

Second, it sounds like you may have an actually pushrod or pedal assembly issue. If there is something wrong with the pedal itself then this could happen. However if there is a fluid leak, you can search all day and it will collapse until the leak is fixed.

 

I have looked it over very close for leaks and can't find any unless the cap is leaking air because of the swollen diaphragm? No fluid loss at all. I also originally thought a pedal issue ... the truck set for 5 years ... I sprayed the entire assembly down with a good lubricant and it didn't seem to make much difference. After thinking about it I f\dont see how a pedal issue would stop it from disengaging ... push rod is completely compressed. I think it has to be in the slave cylinder ... could air in the system or someone putting in the wrong fluid cause this? What is the function of that diaphragm in the master cylinder?

Thanks,

 

Is yours an internal or external slave cylinder? My thought is the throwout bearing is hanging up. on the internal slave that is on the T/O bearing. If you can see up into the T/O & shaft try spraying some lube up on the shaft.

Craig

 

It is internal ... going out to look at it again now.

Thanks,

 

You maybe looking at tearing it down.