Keeping an antique truck on the road.

    I bought an F250 pickup with a diesel engine new in 1983.  It has 160,000 miles on it and gets 22-25 mpg when its bed is empty.   The conventional wisdom is that the engine can easily be run for 200,000 miles without needing major repairs.  When it passed the age of 25 it no longer needed to have biannual emissions tests done in my state.   The major cost of keeping it going is repairing the things that have simply worn out.  In 2008 the exhaust system developed multiple leaks and I fixed those by replacing the muffler and the tailpipe.   A few weeks ago I took it out on the road & had the unnerving experience of having the clutch pedal go to the floor and then had great difficulty shifting from one gear to another.  Once in gear, though, the truck ran just fine, only shifting had become very difficult.  I thought this was due to the truck’s hydraulic clutch activation system, which has already been replaced once, about 20 years ago.  I had the same problem then.  I had this done at a local shop, but this time around I’ll try to fix it myself.
I spent a lot of time on the internet informing myself about the problem.  I posted some queries at the forums on the Ford Truck Enthusiast site.

I created a video of the firewall motion
at the clutch master cylinder   from Youtube.
The problem was well known enough for Ford to have issued Technical Service Bulletins over the decades, and I came across some of these in my search.  I am posting everything relevant here to assist others in solving similar problems.

Here’s a recent thread from ford-trucks.com on reinforcing to fix the too-flexible Ford Truck Firewall.    Many good photos here.   Here’s another related thread from the same forum.

More detailed comment from that forum below:

Weird self-healing hydraulic clutch mechanism

Some months ago I had my 1983 F250HD with diesel & manual trans out for a spin. 
The clutch had been feeling stiffer and stiffer, sometimes the gears would grind when I shifted, at other times normal action.
Suddenly the clutch went to the floor as I came to a stop, I was able to pull the shift level back to disengage the transmission. 
I was able to pull the clutch pedal off the floor & get a little clutch action, enough to limp back home. 
Clutch pedal went up a bit on the way home & I backed the truck into my drive. It has been there for months.
I read up on oil-canning of the firewall, made a video of it on YouTube. The sheet metal movement seemed like very little to account for this.
I disassembled the clutch pedal & rod mechanism, no unusual wear or binding. No firewall cracks. Removed the clutch master cylinder, fluid levels seemed normal, no leakage found. The hydraulic line was translucent plastic, fluid was clear.
Slave cylinder looked OK. I video’d the action of the slave when I got the clutch reassembled, it seemed OK.
I bought Ford’s small firewall reinforcement metal plate E3TZ-7K509-A, but have not gotten around to installing it. The holes that need to be drilled in the firewall & the hump over the transmission look rather difficult to place for a person of my size & skill level.
The clutch now feels normal, so I took the truck out for a spin.
Clutch stiffness seems like new, action of shifting is normal, all is well.
I really did very little, just disconnected & reconnected the pedal linkage, dismounted the clutch master cylinder, jiggled it a bit & remounted.
Would appreciate any ideas about what happened. Never had such an apparently severe malfunction like this, suddenly get better for no reason.
Comment to above post:
When you say you “dissasembled the clutch pedal and rod mechanism”, do you mean you dissasembled the entire horizontal clutch pedal cross-shaft mechanism, or do you mean you removed the clutch master cylinder pushrod from the cross shaft pivot arm (the spot where a single spring clip holds the pushrod to the pivot arm)?

If the former, then perhaps there was binding somewhere in the horizontal cross shaft, and you freed that up by dissasembling/reassembling. If the latter, then perhaps the binding is intermittent and may occur again. It sounds like the hydraulic portion of the system is functioning properly.

Comment to first post:
I can’t offer any genius advise, but I’ll suggest that you install your repair panel BEFORE you need it. I wish I had, I might not have needed the larger repair panel.

Happy wrenching and good luck.

Reply to the first comment:
It was the latter. I just disconnected the pushrod from the pivot arm so that I could dismount the clutch master cylinder from the firewall.
The only thing keeping me from installing the reinforcement plate are the 2 holes I am supposed to drill sideways into the transmission hump – I don’t see the room for even a right-angle drillhead to bite, unless everything in the front of the cab is removed first. The other holes that need to be drilled are straight through the firewall & seem easy to do.
Reply to above response:
I found that the lower of the two transmission hump holes can be drilled or “ground through” using a dremel-type moto-tool. The upper could be drilled from the outside (engine compartment) after installing the plat if one knows the exact distance between the lower hole and upper hole.

But the directions say the two side bolts aren’t necessary unless cracking extends to the transmission hump. I only installed the lower of the two transmission hump bolts.

If you get a chance, could you measure the distance (center to center) between the two transmission hump holes on your repair plate? I forgot to do it before installation and now its kind of difficult to measure.

It’s pretty tight in there, here is a link to a thread discussing this problem, it is just one of several:

http://www.ford-trucks.com/forums/10…ex-repair.html

So, with almost nothing having been done to my hydraulic clutch, it is now operating normally.  I haveyet to install that reinforcing plate, still sitting in its box on my shelf.
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2 Responses to Keeping an antique truck on the road.

  1. The Recliner Commando says:

    From an article from Alldata: "Incomplete clutch release and/or hydraulic fluid leaking into the cab from the clutch mastercylinder may be caused by the reinforcement plate on the clutch master cylinder separatingfrom the dash panel. The separation of the reinforcement plate reduces the clutch mastercylinder pushrod travel. Reinforcement plate separation can also cause deflection of the clutchmaster cylinder that results in a misalignment of the pushrod to the clutch master cylinder.Misalignment causes the "O" ring in front of the secondary seal to leak hydraulic fluid."

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