What do you mean seal?

 

Should I replace the master cylinder or booster?

 

He's saying the seals inside the master cylinder maybe worn. That would be a internal leak.
I've seen a master leak out of the back seal and leak into the booster undetected before to.
You can check it by..
Unbolting it from the booster and pull it out enough to inspect the back of the piston.

 

Okay I will, are there any other seals?

 

More than likely the problem is the master cylinder. The rest of the brake system is pretty simple, and if it's not leaking out of any of the lines or the calipers/wheel cylinders, you can bet that the master cylinder is more than likely the problem.

 

Ya. What about the brake booster. I can do the master cylinder. That's only a 30 dollar part but the booster is a different story, can the booster cause this? I'm going to Colorado about a week after I get back from California and I'd like to have brakes In the mountains haha

 

No fluid enters booster not a air issue possibility .

 

Alright thanks!

 

Replace it with a dual diaphragm booster and MC.

 

That sounds exspensive and I don't have much money to blow before Colorado so I might just get the mc haha

 

96+ XJ at the JY

 

1994 jeep. Haha

 

Don't touch the booster. Not sure why that was suggested... terrible advice.

If the booster were bad your pedal would be stiff (like when you try to brake while rolling with the engine off). Booster is more than likely fine. Even if it wasn't, it wouldn't cause the problem you're having. It simply can't, that's just not how it works.

 

Didn't know. Ill replace the master cylinder when I get back.