Today, I was cleaning up the firewall in preparation of more work. I removed the brake booster and pedal assembly in the cab. I was trying to undo the nuts that hold the clutch master cylinder to the firewall, but was having a heck of a time getting my socket around the nut due to some interference with the sheet metal. I went to the outside and after scraping the old cracked seam sealer, I found the dreaded firewall crack that we have all heard about.

There are several threads about how to repair these cracks with the reinforcement plates, but some of us might not be sure what we are looking for, or exactly where to look, so I decided to post some pictures of what they look like and where they occur. Be sure to scrape away all that cracked seam sealer, too, because it will obscure the cracks. If you don't have any cracks, consider yourself lucky, replace the seam sealer, and definitely consider the installing the clutch master cylinder reinforcement plate.

Crack found after removing the cracked seam sealer.


Closer view of the cracked firewall.


View of the separation inside the cowl resulting in water leaking into the cab.


View from the inside of the firewall.


So if you weren't sure before, now you know what you're looking for. As you can see, the seam sealer covered the crack, so definitely clean up the cracked seam sealer as that can definitely cover up developing cracks.

 

Rep points sent to you Ron, thanks for posting this. Sorry your firewall is cracked, I guess you might have to install the larger-style repair plate.

Is that a crack I see in the last photo from inside the cab, extending downward from the lower master cylinder mounting hole?

 

Thanks, Galendor,
I don't think that is a crack below the lower mounting hole, but I need to get better access to confirm. I was planning to smooth the firewall, and so was going to remove the outer reinforcement plate and move it to the inside of the firewall. At that point, I will be able to examine both sides. I still need to get a wire wheel on the interior side to help determine the extent. Since I will be moving the reinforcement plate from the outside to the inside of the firewall, I may just use thicker stock for the entire plate.

It is amazing how well that seam sealer hid that crack, though.

 

Yes, thanks for the post, and reps for that. Makes me think that doing all the work to rebuild my mechanical linkage wasn't for naught. At least my firewall isn't going to crack.

 

Thanks for the reps, Gary! Hopefully, it will help someone else find whether or not they might have a crack hiding under that ancient seam sealer.

 

Reps given by me as well. Fortunate for me but unfortunate for you, this post only reinforces (no pun intended) my decision to buy the full plate kit from Terrapin Manufacturing and install it when I am working on my conversion. I would make a plate, but I really don't have the time to do so and I don't think his (Jason, I believe) price is unreasonable for what you are getting.

 

If you were going to use the normal plate everyone else uses, you could add those pictures here and make a nice tech tip article for the top of the forum. Post's like this one could be taken out.

Or, it still could be a nice article if your modifications were not too radical. I am not sure what you are doing from your previous description. You have to be careful adding plates, since it can change the pedal geometry. That's why the factory repair plate is mounted on the inside, so it won't move the clutch master cylinder position.

 

I am going to smooth the firewall, and was planning to remove the larger reinforcing plate from the front of the firewall and move it to the back. Because of the bends at the edges, I was thinking about using it as a template and making a new one out of even heavier gauge steel. I may extend the reinforcement panel to match the profile of the aftermarket reinforcement plates wrapping up under the cowl and around the bend into the trans tunnel. While the reinforcement plate is off, I will patch the cracked area. I was planning to plug weld the reinforcement panel to the firewall in a similar fashion to the current panel. I will be posting pictures and descriptions of that in my build log for El Guapo.

So I don't know how useful it would be for a sticky, but I did want to make sure folks knew to look under the seam sealer, and where to look to find the cracks.

 

With the firewall reinforcement plate removed, I discovered that the crack was far more extensive than I would have imagined.



Looks like I've got some significant bodywork to repair this mess.

 

This is the factory plate - right? I'm asking because people are wondering if they need a plate for sure, and if they do will the factory plate do the job. Just wanting to lay it out explicitly for those who might be coming later.

 

He took the factory plate off, which fails to do the job and lets it crack. They add a big plate on the inside with bolts running up through the top to fix something like this. It looks like a real pain to install if you are not tearing it down like in the above pictures.

Here's a link from another board with more info on the whole deal.
http://www.oilburners.net/forums/sho...at-to-do-PART1

http://www.oilburners.net/forums/sho...p?44519-Part-2

 

Thanks. I thought that was the situation, but wanted it documented - especially since someone on here is thinking about that issue.

 

The last picture in #9 is the firewall, after I removed the factory firewall reinforcement plate on the front side of the firewall in the engine bay. I was going to smooth the firewall, anyway, so was planning to remove that factory plate (the one with the edges bent at 90 degrees).



And with the plate removed.



As you can see, the plate also covers the crack where it extends into the upper section of the firewall forming the front of the cowl and did result in leaks in the cabin, but fortunately, my floorboards are not rusted.

To install the reinforcement plate on the inside you don't have to remove this plate that is on the engine side of the firewall, but I removed it because of what I am doing as part of my resto-mod. Here is the plate that I removed from the front (engine) side. You can see all the spot welds that I had to cut to remove it.



Based on my experience, I would recommend anyone who plans to keep their truck with a manual transmission, to install the reinforcement plate that goes on the inside of the firewall. At this point, I think Terrapin Mfg. is the only source for those plates. It will be a pain, but it may keep you from having to deal with this.

 

Heres my write up on it.



https://www.ford-trucks.com/forums/1...l#post11358654

 

Good advice. But, don't forget the other option - mechanical linkage. I've not had a hydraulic linkage nor had to repair or even reinforce a firewall. And, I do remember the problems I had getting my mechanical linkage up to snuff. But, in comparison to the problems with a cracked firewall I'm wondering if my pain wasn't minor. Having added Oilite bushings I'm fairly confident the wear is under control, and I don't have to worry about cracks.