They put a gasket there for a reason: to keep engine bay fluids (water, hydraulic fluid etc) from leaking into the cabin and staining the carpet. It wouldn't help a catastrophic master cylinder failure but they usually fail internally first, and show it as inability to maintain pressure (sinking pedal or dragging clutch etc.).

There is an issue if the brake master cylinder sits too low. There's a metal plate that is under the master cylinders and if that's not in place you will have major brake issues. You see, the pushrod goes up to push fluid through the lines. After the peddle is released the pushrod must come down enough to open up the hole that allows fluid to return to the can. Without that metal plate the fluid can't come back out of the lines into the can. I don't know if not having the gasket would cause the same issues, but I wouldn't chance it myself.

No, but if you use a custom cork gasket for example, you will compromise the clutch operation...

 

...guess how I know ?

With the master out, the pedal is pulled all the way back by its return spring. When you install the master, you have to push the pin through the master's pushrod clevis and through the hole in the pedal.  If to install the pin, you have to push the pedal down slightly to get the pin inserted, that means the pedal/spring is going to fully retract the master pushrod.  If you have to push the master cyl pushrod up to get the pin through the bottomed-out pedal hole, then you have a problem needing the master to be lifted up.

I would not think it would make a difference as the gasket is rubber/foam and is going to compress when installed.

Hey all,

 

I had to replace the clutch side upper dogbone engine steady, and as a part of that, removed the clutch and brake masters, dicovering that I didn't have the seat gasket that goes between the bulkhead and the metal plate stabilizer bracket that the master cylinders bolt on top of. 

 

Not the individual gaskets that go under each master cylinder, but rather the larger gasket that goes under the plate between the plate and the body.

 

I'll be installing this gasket,  but my question for this crew is, can not having this gasket in place have an effect on braking, by changing the throw of the pedals?  Can I expect a different feel once the gasket is installed?