I have a 1985 F150 with the 300 Inline 6 cylinder with a 4 speed Manual Transmission.
A week ago I started having problems changing gears. If I pump the clutch pedal repeatedly from anywhere to 5 to 10 times, The transmission will change into first, second, third or reverse. After a couple of minutes of driving or sitting this repeated procedure has to be started all over again.
I replaced the Clutch Slave Cylinder and the Clutch Master Cylinder. I have bleed the system more times than I care to say, But this situation has remained the same.
My question is "What else could be the problem?"

Thank You

 

Welcome to FTE.

Check your firewall where the master mounts. '80s trucks are famous for firewall flex, rust and cracks. Watch the mount area while someone works the clutch.

There was an Ford part to reinforce these. Afaik, those are all gone. Not sure if this aftermarket item is still avaiable:

Terrapin Manufacturing

 

I checked the firewall inside and out for cracks and rust, Everything looks good.
When I bought the truck back in October rust was one of the things I looked for and the lack of rust was the main reason I bought the truck.
After bleeding a few time these past few days, I checked out the C retainer and now I am wondering If I put the slave cylinder C retainer on the wrong side of the bracket.
I have looked in my Ford Truck manual and the internet for a decent photo for it's placement and none are to be found.

Thanks For the Help

 

I had something odd happen with my 80 E150. I went in a ditch when I hit pretty much glare ice (going all of 20 mph -- it was slippery). Anyway, the tow trucks were backed up for hours, so I got pulled out by some semi crazy guys with a 4WD.

Later, I had clutch issues and put it in the shop. The floorboard was cracked and flexed when I pushed on the clutch pedal so it wouldn't completely release.
Maybe you didn't check that area. A long shot, but who knows.

Also, you might try asking up in the 80- 86 section of the forum. More folks up there with vehicles of that era.

Good Luck,

hj

 

The F series, which is what the OP has, has the flex problem on the firewall where the master is located. I suggest even though the OP has no cracks or rust that he check the firewall for flex. Have someone work the clutch while you watch it, or hold on to it.

On the E series, the master is on the floor and they also flex. I made my own reinforcment for my '85, with good results.

 

If the pedal sinks and there are no visible leaks, it's a bad master cylinder. Otherwise, look for leaks. You may have an air intrusion issue at the master or slave hose connections, those o-rings are easily damaged if you did not push the hose straight into them.
Something that may work is a vacuum pump adapted to the reservoir cap, I have used a rubber drain stopper with a hole drilled in it with good results. Put this on, put vacuum to it, and have someone pump the pedal while you watch the reservoir. If there are bubbles percolating up into the reservoir constantly, you have an air leak somewhere.

 

85e150six4mtod, ford2go, Ford_Six
Thanks for the responses and advice.
In the 300,302,351 models of Ford truck(I think Ford used this type clutch system from 84-87)they used a semi clear, red plastic tubing that one can see through. With a small flashlight I can check the tubing for air bubbles.
They used pins to hold the fittings into both the clutch master cylinder and the clutch slave cylinder. No O rings, Those same fittings are pressed into the tubing and can not be replaced separately.
The tubing comes with fittings already pressed in, And costs the same as a new clutch master cylinder. When the weather permits I am going to replace that also.
I thought the throwout bearing might be the problem(lack of grease), Because an inexperienced mechanic replaced the clutch, pressure plate and throwout bearing last September a month before I purchased the truck.
I do not know if the pilot bearing was replaced during that process.
When I pump the clutch pedal enough times for the transmission to finally change into first or reverse, And then I keep the clutch pedal pressed to the floor for several minutes. I have to start pressing to pedal over again to change onto first ot reverse.
It seems to me there is still a problem with air in the system or the new clutch master cylinder or the clutch slave cylinder was bad.
Thank Again

 

Ok, if the pedal doesn't sink then there is still air in the system. There are o-rings, they are inside the bore of the master and slave that the hose ends fit into. The protruding nose of the tube fitting seals in these, and if the fitting is inserted at an angle they can be torn. Seen it happen before. I would suggest having an assistant help bleed it like a brake system, or let it gravity bleed for a few hours while keeping the reservoir topped up.