I have an F150 1990 model 2wd 4.9 liter. and I am having clutch problems. I have replaced the clutch slave and master cylinders. I have bleed about a half gallon of fuild through the system yet I still can't achieve a consistant firm pedal. The pedal will pump up, then go soft again after a moment. The pedal will go to the floor and return slow or not at all. The fliud will drop then literally gyser out the top at times. It has the 3/4 bore master and no bleed screw and forget taking the retaining pin out to bleed at the line. Any suggestions?.....

 

Try "Pumping" the slave cyinder 20-30 times WITHOUT opening any bleed screws. Depending on the trans (4 vs 5 spd) it may have an internal slave inside the bellhousing. You can pump that slave with pry bar by removing the inspection plate. Doing this, forcesany air bubbles to the top of the system and out the master cylinder vent. Generally works. Let me know how it works out.

 

How did your clutch problem turn out? I have a very similar problem with my 1990 2 wheel drive F150 with the M5R2 manual transmission. I recently put a new clutch in, but did not change the slave cylinder or the clutch master cylinder. I have a very low pedal and have tried bleeding it several times to no avail. Jim