Alright. So here's the deal. A few weeks ago, the bottom bolt of the clutch master cylinder in my '85 F350 (460, T-19, 2WD) ripped through the firewall, leaving the clutch system hopelessly inoperable. I had to get to a place that I could fix it somehow, right? So I had no choice but to start it in gear, and shift without the clutch to get to the shop. In doing so, I destroyed both the ring gear on the flywheel and the gear on the starter. Well, I knew that those were both toast, and the clutch was starting to slip. However, I didn't have the time to send the flywheel off to have it turned so I ordered a new one, and I figure if I'm doing a flywheel and a clutch, I might as well change the slave cylinder too, right? Well...

I got all the necessary parts on Tuesday. Flywheel, slave cylinder, and starter came from O'Reilly's, and the clutch kit came from Napa. Long story short, the past two days have been spent changing this clutch, flywheel, starter and slave cylinder, and now my clutch won't disengage, the pedal will only return part of the way from the floor, and the truck won't go into gear at all... Great.

So Immediately, we eliminated a few possibilities. We bled the clutch. And bled it. Flushed it, and bled it again, to no avail. I checked to be sure that when the clutch was pushed in, that the slave cylinder was engaging the clutch fork, and that the clutch fork was properly engaging the throwout bearing. All is well on the bottom side. The only thing that I can think of is that there's enough flex in the firewall that the master cylinder pushrod isn't long enough to make up the difference... Any ideas???

Jeez, don't you love it when your only vehicle leaves you stranded?

-Jake

 

Oh, and I forgot to mention that a piece of the bellhousing broke off, too, where the top clip of the slave cylinder clips on to it. However, there's a solid piece of metal behind the broken piece that's rather solid, and it looks pretty obvious to me and the rest of the shop that I didn't break it, rather it was broken a long time ago. But, broken piece or no broken piece, the clutch still operated before I swapped in the new clutch/slave/flywheel, although the pedal sometimes had trouble fully returning to normal position from the floor. I was able to place the piece back onto the bellhousing and clip the new slave cylinder over it and the slave cylinder seems to hold it in place pretty well.. Maybe that's making a difference, who knows. I'm just stuck, and I need to figure it out.

Thanks, guys.

 

If the firewall is ripped out, that will cause a clutch problem.

I had that happen to my 84 F250, after fixing the firewall, a few weeks later the clutching problem came back! I found a bushing on the clutch pedal push rod wore totaly out, that gave the same thing as the firewall flex issue.

I fixed that problem and years later the clutch MC blew on me while pulling a 37' class-A motorhome home, that was fun to tow without a clutch!

 

Attached is the .pdf of the Ford Clutch Firewall Repair Technical Service Bulletin, in case you don't have it.

 

How did you fix the fire-wall? You never said. Is it still flexing?

 

Well. To re-attach the master cylinder to the firewall, I first smashed the existing one off the firewall with a hammer. In part, because the nuts on the inside of the firewall were being very stubborn, in part because the bottom stud on the master cyl. was spinning freely inside the master cylinder, and partly out of sheer frustration. I then took a torch and went to the shop's wrecked parts car (a 2000 something model Crown Vic) and cut a plate out of a flat part of the frame. I drilled a hole in the plate for the bottom bolt hole to come through, and just kept cutting and grinding until the plate fit, and bolted in a new master cylinder. It worked great, but the pedal still wouldn't return all the way every time it was pressed. I've had a problem with the clutch pedal hanging up in the middle of the travel since I bought the truck..

I shot a few emails back and forth with Jason at Terrapin MFG about one of his firewall re-enforcement kits, but they're back ordered and won't be available to ship until Monday, and it'd be here by Thursday or Friday at the earliest. I may still order one, but I'll be working Thursday and Friday, so I'm thinking about trying to see if I can't fabricate a larger re-enforcement plate of my own during my off days on Tuesday and Wednesday. I don't have, nor do I have access to or the money for, a CNC machine or a plasma cutter, however, I do have access to a torch, a grinder, a cutoff wheel and various other pneumatic tools. So if I can find the proper metal, I might be able to make one..

To answer your question, yes, the firewall is still flexing, though not as much as it was before I put a band-aid on it, but that still seems to be what's keeping the clutch from dis-engaging. Unless the piece that broke off the bellhousing is making a difference, but I doubt it, as it looks like it had already been broken, and was being held on by the slave cylinder. I suppose that it's entirely possible that either I got the wrong slave cylinder, or the slave cylinder doesn't have a pushrod long enough to move the clutch fork far enough forward for the throwout bearing to fully release the clutch.

 

On that plate you put on, what was the thickness of it?

Here's what I'm thinking: If you put it on the engine side of the firewall, with the added thickness, the pushrod may be too short to complete the stroke resulting in an incomplete disengagement.
Possible?

 

Absolutely possible!
Heck, even the thickness of the plastic retainer clip is enough to defeat pedal return and disengagement.


Jake,
Some new user here had a pic of their 'new to them' truck with a length of 2x4 wedged between the clutch master and the radiator support!

But hey, if it works on a temporary basis until you can take the time to fix it right...
At least it will get you to work.

This is an issue with all these trucks, and the more times it flexes the worse it gets.
Adding the small reinforcement plate to mine -before- any damage was done helped my clutch action immensely.

With the kit at least the holes will be in the right place and you can set to R&R instead of spending hours to cut, fit, mark, trim, fit, mark, drill, etc.....

Sounds like you have a pretty short fuse already.
Why put yourself through all that?

 

Sounds plausible, however, the plate was put on the cab side of the firewall. It's not very big, either, about the size, or maybe just a bit bigger than a fender washer. I'm not sure how thick the frame of a Crown Vic is, but I'd say it's about 1/8" thick. The plate's basically just big enough to cover the hole that the bolt ripped in the firewall and give the MC something to bolt to.

I might have to try that 2x4 trick. I never thought about that. But you're right, it'd get me to work. Fortunately, my dad's been gracious enough to let me borrow his truck for the next few days, so at least I'm not without a vehicle yet.

I'm going to hit the boneyard on Saturday and see if I can find a re-enforcement kit for it. If not, Tuesday and Wednesday are going to have to be spent fabbing up a re-enforcement plate, as I can't wait until Friday to get a kit, nor do I have $100 to spend on one.

And generally speaking, I'm pretty patient about everything. But after spending two days, having to go through three different flywheels to get the right one, having to make a pin that holds the shifter in place after the original was somehow lost, still owing Napa $150 for the clutch, and getting it all back together to find that it doesn't work, I'm pretty frustrated about it. But, having a day to cool off and come up with a solution is going to do me some good.

Thanks again guys, for the ideas and wisdom.

 

As stated in the TSB, you can check the release bearing travel distance to determine if the pushrod is moving far enough to disengage the clutch.

Tools required are an assistant to push the clutch pedal in while you measure the distance traveled using a ruler underneath the truck. Release bearing travel, measured at the clutch slave cylinder, should be 11mm or more if working properly.

If the slave cylinder is loose in its broken mount, and can wiggle around, then that amount of wiggle room will also not be going into clutch travel. Any movement at either the master or slave cylinders when you push the clutch pedal down is movement that is not being put to work disengaging the clutch.

 

Gotcha.

I was thinking something was fabbed up that went under the whole master.

 

Success! ...kind of. I finally got the truck to go into gear! ...sometimes...

So, I went down to a junk yard in Griffin (my new favorite boneyard, so many Ford trucks, so many great parts.), and found one of Ford's 'minor' reinforcement plates, and grabbed it for $5. I took the plate back up to the shop in Stockbridge where the truck currently sits, and "installed" the plate. I just unbolted the clutch master cylinder, installed the plate, and bolted it back down. I haven't drilled the proper holes for it yet, but that's coming. It did take about 80% of the flex out of the firewall, and I'm sure that when I bolt it down and fully install it, the flex will be gone.

So, with most all of that flex gone, I was excited. Fired up the truck, went to shift it into gear, no joy. I spent the next hour or so pumping the pedal, bleeding the slave, pumping the pedal, bleeding the slave, flushing the system and repeating the process until I finally got a great pedal feel. Even though the pedal felt great, it still wouldn't go into gear. So I sat there, motor running, pumping and pumping on the pedal, and finally it slipped into first. With the pedal still depressed, I was able to move it in and out of all four gears, plus reverse freely. I released the pedal and stepped on it again to see if it was cured, and it wouldn't shift into any of them. Pumped it a few times and held it again, and I could again shift into all gears. So my problem now is that I can shift into all gears, but I have to pump the pedal a bunch of times first... That leads me to believe that either air is somehow getting into the system, it's leaking fluid somewhere, or that it was improperly bled. I'm suspecting the O-ring in the inlet of the new slave cylinder... Any ideas?

 

Can you get help to measure if you have 7/16" of throwout arm travel as Galendor stated in post #10?

 

I did forget to mention that I put a tape measure on the clutch fork, and measured 12-13mm of clutch fork travel, so I think I'm good to go there. However, while I was taking my measurements, I repeatedly had my dad push the clutch in and let it out so that I could measure the travel, so that 12-13mm might only be that much because the pedal had been pumped a few times.

 

Okay, I just wasn't clear that you had the required travel.
Sorry if I missed that.

I bet things will work once you get those bolts in the tunnel and cowl.