Odd Clutch Behavior (pedal to floor when hot)
 

I have a 1992 F150 4x4 with 5 speed manual transmission. The clutch works great until I travel ~30 miles at highway speeds (~65/70 mph). Upon exiting highway the clutch goes to the floor. I can pull up pedal with foot and pump to get a little bit of clutch. Once cool the clutch works great again.

I've replaced the pedal bushings and the bushing to the master cylinder rod.

The fluid level is fine and there is NO fluid on ground or on bell housing.

Anybody have a solution for this?

Master/slave? I hope it is not the slave cylinder.

Thanks,
David

just joined this forum, my 94 f150 4x 4.9 5spd has the same problem, same solution. My pedal went to floor but temp is around 7 degrees.. when ford put the slave inside the bell they did not do us any favor.. I am hoping to slide it all back and access slave.. Its a job I am not looking forward to at 7 degrees, hope you are in a warmer place..
David from Goldendale wa

Same problem? Does it only happen after driving long distances without stoping and going (for example, Interstate)?

I don't have a solution. Don't want to replace slave until I know that is the issue because it is not easy and it is cold.

you have a problem with clutch that occurs when hot, the slave is inside the bell and subject to extreme heat, the master is not as for my problem happening at sub freezing temp the master could be the problem doubtful though. The pedal moves freely. The slave is subject to extemes and more likely to fail.. Just co miserating, Sorry if I have wasted your time.. David

You are never waisting my time :)

I was thinking about the heat within bell housing but it has never failed during a LOT of stop and go driving.

Hi David
I had worked my truck hard day before no issues no indication of problem.
Next morning with temp at 7 degrees I started truck, pushed clutch in once to start still no issue, let warm up a good twenty minutes.. came out to go, pushed clutch in and it stayed on the floor. same as you, resivior full and no signs of fluid anywhere else.
have you tried to bleed slave? you can get a master cyl at amazon for 30.$ part #
LuK LMC177 Clutch Master Cylinder

slave part #
LuK LSC003B Clutch Slave Cylinder

comes with brg for 44.$
Soon as I quit being disgusted I will go try bleeding system.
I am going to youtube to continue my education.
good luck, if I find somthing helpful I send it your way