Flex in the fire wall do to rust

[Lorenz]

I have a 1986 jeep comanche x with a 5 speed and when you press the clutch in the fire wall flexes witch is not allowing  my clutch to fully ingage or disengage can anyone help me figure out how to fix it ?

[Pete M]

pics of the damaged area?

[Lorenz]

1 minute ago, Pete M said:

pics of the damaged area?

Truck is on its way back from my mechanic  but the damage  location  is at the master cylinder  and brake booster 

 

[Lorenz]

Will send damage pics as soon as the old girl is back home should be this week 

 

[Pete M]

it is common for a leaky master to eat up the paint and the fuse box, but I can't remember seeing one so bad as to start affecting pedal travel.  

[Lorenz]

2 minutes ago, Pete M said:

it is common for a leaky master to eat up the paint and the fuse box, but I can't remember seeing one so bad as to start affecting pedal travel.  

Yah it's got me worried  tbh hope I can fix it 

 

[Pete M]

the good news is that it's just steel.  you can add more as-needed.  

[gogmorgo]

Should be able to cut a chunk out of an XJ firewall and weld it into yours.

[Lorenz]

22 minutes ago, gogmorgo said:

Should be able to cut a chunk out of an XJ firewall and weld it into yours.

So I should  be able to take a chunk of fire wall from a 1986 xj and weld it in 

[Eagle]

Don't forget that the XJ started in 1984. '84 thru '86 should have the same firewall -- the change was in 1987, to allow for the 4.0L inline 6-cylinder engine.

 

[gogmorgo]

Would the master cylinder section of the firewall have changed for the 4.0? I thought that was just the centre section. 
 

Failing finding a matching chunk of firewall, if you figure out where it’s damaged, it shouldn’t be a ton of work to shape something functional out of new metal. Even if it’s just a plate acting as a large washer to spread the load out. Just be careful doing that that you aren’t interfering with spacing or you might affect clutch throw.

[dasbulliwagen]

 

21 hours ago, gogmorgo said:

Would the master cylinder section of the firewall have changed for the 4.0? I thought that was just the centre section. 
 

Failing finding a matching chunk of firewall, if you figure out where it’s damaged, it shouldn’t be a ton of work to shape something functional out of new metal. Even if it’s just a plate acting as a large washer to spread the load out. Just be careful doing that that you aren’t interfering with spacing or you might affect clutch throw.

 

The clutch master is different between 84-86 and 87 and later. I had that issue when I swapped an 86 AX5 with external slave into my 87. The clutch master bolts are rotated 90 degrees between them. 

[87Warrior]

Does your truck have a support bracket running from above the drivers side kick panel to one of the clutch master cylinder mounting bolts? This bracket helps prevent the firewall from moving around when the pedal is pressed. 

[schardein]

On 2/1/2022 at 11:26 AM, 87Warrior said:

Does your truck have a support bracket running from above the drivers side kick panel to one of the clutch master cylinder mounting bolts? This bracket helps prevent the firewall from moving around when the pedal is pressed. 

BINGO

 

It's common in the Jeep CJ world to see people convert to a hydraulic clutch (factory option with 4 cylinder models), which is so much better than the stock mechanical linkage (on 6 and 8 cylinder models).  What they often forget is the factory bracket that ties the pedal pivot pin into the firewall at the point where the clutch MC is mounted.  It also adds convenience, as the studs for the clutch MC are made into the bracket.

 

First pic is a late YJ bracket and an early YJ/CJ bracket (different spacing).  

 

next pic is the 86 MJ parts manual, which interestingly, doesn't show a reinforcement bracket.

 

last pic is from 87-90 parts manual, which shows a reinforcement bracket.  

 

Can anyone confirm that 84-86 XJ/MJ had the reinforcement bracket?

[1stDeuce]

 The '84-86 master cylinder has horizontal bolts, with a bracket (rod, actually) that goes from the outboard bolt over to the kick panel to stiffen things up, just as 87Warrior suggests above.  Perhaps someone took that rod out at some point?  I suppose it only helps on the outside bolt...  If the firewall was REALLY rusty, the MC could flex to the side some, and that would probably eventually break the brace... 
 
The '87-96 MJ's and XJ's have vertical bolts, and the service manual image from Schardein shows that there is indeed a brace with that one too... 
Without it I can't see how it would live, as the lower bolt hole is on a thin strip of metal between the fuse box opening and the hole that the MC rod goes through...   As I am trying to convert to the '94-96 MC and slave setup, I will have to try to find one of those brackets...  No JY's near me will let me out into the yard.  Totally sucks for stuff like this where I just need to have a look.  This thread likely saved me from having a firewall strength issue down the road...