I found a few posts on this and I think I know what it is, but I'll ask anyway.

Sometimes, usually after sitting in traffic with the clutch depressed, it doesn't come back up. If I pull over and shut off the engine and pull it up with my toe, it seems to be fine (for awhile). My interim solution was to shift into neutral at stoplights. The other day I went to move it to the other side of the driveway and it did the same thing straight away, so now I think I have to act on it.

It seems like the hydraulics may be going out. Lots of people mention what a PITA it is to bleed the system and others talk about pre-bled master/slave combinations.

Can anybody recommend whether or not this is a task for a person who doesn't do a lot of work on their own vehicles? Can I get a pre-bled system for a 1986 F250 6.9L IDI engine?

 

First check all the bushings and pedal pins for wear on the clutch/brake frame assy under the dash. Check the firewall for flexing near the booster (cracks also).

 

do u have feuild in the clutch

 

That was my first thought - check the fluid.

The reservour was pretty full, but it had this real funky piece of rubber in there that didn't seem to be connected to anything. It didn't look like the ones I have seen in the brake's master cylinder.

 

try this blead out ur hole sysyem

 

No use to try bleeding the system, I bleed mine by driving it.
The master cylinder is the high point in the clutch system, as you drive any air in the system will work it's self to the master cylinder.

When you say it sticks.
Is what you are seeing is the pedal returns about 1/2 way up, and then just stays there?

My guess is one of two things.
There is an assist spring that helps you hold the pedal down.

Either the firewall is cracked, and letting the master cylinder move away from the pedal arm enough that the assist spring is holding the pedal down or the master cylinder is bypassing fluid internally which then lets the assist spring hold the pedal down.

Have someone push the clutch to the floor while you watch the master cylinder.
If it moves more than a very tiny amount, you have cracks in the firewall around the master cylinder.
Ford used to have a mend plate to fix this, but it may be discontinued by now.
I fixed mine with a 3/16" thick steel plate about 4" square.
Drill a hole for the master cylinder bolts and the piston rod, un bolt it and unhook the rod.
Slide the plate over the rod from inside the cab, reinstall the nuts and hook up the rod.

If the master cylinder is bypassing fluid internally, you need a new master cylinder.

 

Thanks Dave, I'll try your tests this weekend.

It does seem like the pedal comes up a little, but maybe not half way. When it is stuck the transmission is engaged so I guess that means it must be coming up a little. I used to have a perfect little piece of metal to use for a reinforcement plate otherwise I've seen that Ace sells them.

In some ways though, it seems like it might be the master cylinder has leaky seals. My son and I theorized that this is why the problem occurs when you've been sitting on the clutch for awhile.

I have the factory repair manuals and I'll have to see if changing the master cylinder (if necessary) is within my capabilities. And I didn't see anything in there about how to bleed it, but there must be a bleeder valve on there somewhere.

I will post back once I have a diagnosis.

 

My 90 F250 is doing the same thing and I know it has a bad master cylinder. If it sits for a while and I want to drive it I have to "PUMP UP" the pedal to get it to where I am able to disengage the clutch with it. I am going to have to put a new master and slave cylinder setup on it (after my new tranny with external slave cylinder goes in this month with the 7.3l).

By the way if you have the external slave cylinder (located on the outside driver side of the bellhousing) then "yes" you can get a pre bled system for your truck. If you have an internal slave cylinder (located inside the bell housing of the transmission, all you will see is a line going in and a bleeder valve sticking out) as far as I know you cannot get pre bled setup because it has to come apart to instal the concentric slave cylinder (this is the setup that mine currently has, because it still has the orignal 5.8l and matching ZF5 which is coming out this weekend).

If you have the externall slave cylinder then it is a very simple install and I would say that you would have no trouble at all changing it. If you have the internal then you have to pull the transmission or engine (your choice) to change the stupid slave cylinder (might as well change the clutch while you are there, if it worn much at all). For your sake I hope you have the external.

If you need I can scan the pages out of my shop manual and send them to you with the procedure for changing out the slave master cylinder setup. Bleeding is not too bad if you have an internal but as others have said it will take care of itself after you drive it for a while, you just need to bleed it good enough that is actually depresses the clutch fully at first and the rest of the air will come out in time.

 

if the master cylinder was leaking internally the clutch would engage while holding the pedal down , liek dave said the overcenter spring could be an issue also the pedal bushings are probably completely worn out which will cause the issue and there is also the firewall cracking
bleeding the slave cylinder , whether its an internal cylinder or an extrenal
pump the clutch system up with the pedal
then go under the truck and compress the slave cylinder with a pry bar and release it slowly do this several times
you are not trying to release the clutch just the opposite
it forces the air back up to the master cylinder and out into the resevoir

 

I spent some more time looking at the Ford this weekend. I rechecked the fluid and found it was actually a little too full. The shop manual warns of overfilling and says that it is especially important to leave some room in there as the clutch gets older and more worn out.

So, I took out a little fluid and the clutch seems a little "looser" if you will, but still was functioning well. I did not see any problems with the firewall being cracked and I did watch the slave cylinder while my wife pushed the clutch in and it does move the required .53" or better.

By looking up under the dash, I could not really see the spring that assists with the release. The clutch pedal seems to be a one-piece unit and I now suspect that the problem lies in there somewhere. I'm hoping that maybe just a shot of WD40 will fix everything!!!

Thanks for all the pointers - I need to check the pedal bushings next I think.

 

I actually had to replace the clutch lever.
The bushing wore out, and the pin on the clutch lever was almost half gone before I noticed it.
That is the only thing I had trouble with under the dash in 430,000 miles with lots of shifting.