Gary,

The measurement you need is movement at the clutch arm.
(or slave extension)

More than 5/8,.... 3/4 is better

 

Did you put a bronze washer on the outboard side?

 

Gary, the "bag" was also used by some as an emergency supply of fluid. Easiest way I used to bleed those is straight out of a Mercedes-Benz manual, use the left front caliper to reverse bleed. Take a piece of hose that fits snugly over the bleeder screws, loosen the clutch slave bleeder about 2 turns and then with the hose connecting the slave to the left caliper, bleed the caliper through the clutch system. It works well on them for two reasons, first the master cyls use a common reservoir, and second, the M-B clutch master is on an angle under the dash and really can't be bled normally.

One thing to look at, in addition to the previously mentioned firewall flex, these are famous for breaking the rivets holding the clutch fork pivot in place, and have been known to crack clutch housings and release forks. The whole idea of the hydraulic clutch when Ford returned to them was it is pretty well self adjusting as was my Mercedes-Benz 220SEb.

 

Jim - I think I understand about the "bag". But, how much fluid do you put in the reservoir? Is there a line in there that I didn't see? Obviously you can't fill it full or the bag would cause it to overflow.

As for the bushing, I cheated - the one shown was the first one I did and it did turn out to be too thin. So I made another one that was a press fit, but installed it before I took a picture. And, I didn't put a washer on it as the pushrod doesn't seem to have any tendency to move sideways. But, I could make one out of the thin bushing and install that - if you think it is needed.

And, I appreciate the measurements. The reservoir is dry, so that's surely the problem. Tomorrow I'll fill it and bleed the system. Having my wife push the pedal to the floor and then cracking the bleeder seemed to work well, although this time I think I'll put a hose on it to direct the overflow down instead of everywhere.

Matthew - It just hangs down into the reservoir as it is way too big to go into the cap.

Bill - I don't think I want to put fluid from the brake system into the clutch system as the brake's fluid is rusty. In fact, I plan to flush that system soon and file the top of the master as it is rusted enough that the seal is leaking. (Obviously I'll ensure filings don't get in the master.)

As for the rivets, I'll check that out. Thanks. But, I'm pretty sure the problem is the lack of fluid in the clutch master cylinder.

 

And, I checked out the cowl seal's RTV, which had been curing for 48 hours. The seal was well glued to the cowl, so I closed the hood and the seal appears to have fit to the hood nicely - it is easy to tell because you can see the seal in the gap between the cowl and hood.

Also, I did take a picture of the bushing that I used, but forgot I'd done so. Looks like the camera focused on the retaining pin as the bushings are out of focus. Anyway, here 'tis:

 

At least you have a retaining pin and not the four finger 'click on' bushing like my bricknose truck.

There should be a fill line or step in the master cylinder reservoir

If you find an aftermarket slave cylinder with an actual bleed nipple it is pretty simple to backfill the system with a Mity-Vac or even an irrigation syringe.
The Exedy SC729 is available on Amazon

 

I will look for the step or fill line. And, it has a bleed nipple, so must be aftermarket. However, Vernon supplied me with a replacement slave cylinder.

Which begs the question of "Why?" Why did he have a replacement, although he had a replacement for almost everything as he was making the truck new. And, why did the clutch start dragging? Is there a leak that Vernon knew about? Or, has it been low on fluid for a long time, with the top-up fluid going in the bag instead of the cylinder?

The fender apron below the clutch master was damp with something, but it looks like it has been coming from the brake master as the paint is peeling from the brake booster and the sides of the brake master were damp. I've cleaned all that up so I can see where the leak is coming from there.

Also, the boot on the clutch slave was gooey - but only on the outside as the inside was dry. So I've attributed that goo to the front main leak. In fact, I'm not seeing anything that tells me the clutch system has a leak. Given that, I'll fill it up and hope for the best.

 

I have a question that I have not been able to figure an answer to.


On a brake system if a master is bad when resting your foot on the pedal it will "sink" to the floor.


How can you tell if the same is happening to the clutch system?
What if it was the slave that was doing the same thing and the piston was letting fluid pass by but not leak out?
Dave ----

 

On a master, depending on where the leak is, if the fluid leaks past the piston it'll go back into the reservoir - as shown below. But on a slave cylinder there's no place to go but "outside" if the fluid leaks past the piston.

 

Thanks Dad had a Mazda that it now looks like the clutch master was bad. Truck was scraped because of it as I did not have time to look into it deeper.
Dave ----

 

You guys were right - the hydraulic brake system is a pain to bleed, and it takes driving it to get the bubbles out. My wife and I bled and bled but in spite of getting a stream of fluid w/o air out of the bleeder we still had too much play and the clutch wasn't releasing. Finally I started it in gear and drove it around the neighborhood for about 10 minutes. By the end of that drive you could put it in Neutral w/the clutch down, wait a few seconds, and then put it in Reverse w/o clashing the gears. And, the engagement point has moved up significantly on the pedal. Plus, shifting is much improved.

Also, along the way we found another problem. When I was watching the clutch master and asked my wife to push the clutch pedal down I saw the brake master move. But, she assured me that she was pushing only the clutch pedal. And, when she hit the brake pedal the brake master really moved. So, I slid under the dash and found this:




Tightening those isn't easy, but it isn't that hard. So, why would someone leave them that loose? Even the bottom ones weren't tight. But, they are now all TIGHT and the brakes are much more firm. Plus, the click or clunk that was up under the dash when using the clutch has gone.

 

Maybe someone forgot to torque them and then vibration loosened them. Just guessing

That truck is really coming along!

 

From what I remember those are what is called "prevailing torque" nuts, they look like someone (Godzilla) stepped on them and take a bit of effort both on and off. The top ones are a pain because you need either a medium depth socket + a universal or a medium depth socket with a universal in it in order to get more than a very small amount of rotation.

 

Amen, brother! That's exactly the combination I had to use, and the rotation was very small. And that's exactly why I'm pretty sure they didn't get tightened originally - meaning whenever the master/booster was replaced. But, they are now.

Ok, two other things. First, the fuel gauge reads Full or Fuller. IOW, it reads from the Full mark or higher. I assumed that the wire is grounded somewhere, but today I pulled the 4-pin connector off the tank and the gauge (nor the pump oddly enough ) worked. So I put a meter on the sending unit and got 63 ohms. If I remember correctly the sending units for these should be 12 ohms at full scale to 72 ohms at empty. So, the gauge should be reading about 1/4 tank. Right? Gotta go study that a bit.

Edit: The tank probably has 16 of its possible 19 gallons so the gauge should be setting on about 3/4's. And, if my math is right, that should be around 27 ohms, assuming the senders are linear.

Also, since I got the truck the front tank's filler looked like this, with no cap:




Without looking at it I've tried to put a cap on it, but none of mine worked. Then I found a threaded cap that Vernon sent, brand new in a box, and installed it. So, obviously, the filler neck has been changed out, which may explain why it is almost impossible to fill the tank w/o tripping the station's pump off. Is this a later model neck? If so, did maybe they put the earlier central hose in? Thoughts, please.

 

Gary, the earlier filler has the filler pipe going down the outside if I remember correctly and the later design is reversed, filler is the inside tube and vent goes up around it. If the inside tube (hard plastic) was left out of either style it will be a royal bitch to fill. I would first look at the parts CD and see if it has a good picture of the filler hoses.

Yes, that does look like a later filler neck, and may mean the tanks were updated. Since Big Blue has the in-tank pumps I think from what I remember on Darth, removing a tab on the pump/sender assembly will let it fit the 1987-1993 tanks. Dead giveaway is the permanent "unleaded insert" Darth had a place for one which was a plastic one in 1986 but they were never installed as these trucks did not have to have unleaded only. My fillers use the same screw in cap with no restrictor since I took them of a 1996 Powerstroke dually. I can get a picture of one tomorrow for you, it is dark and damn cold out right now.