I have a 1991 XJ and my brakes are not working super well. I have to put a lot of pressure just for it to stop and the pedal feels pretty stiff. I don't know if it is because of the ABS system or what. I haven't checked to see if there's air in the brake line or if there is low brake fluid but it doesn't leak fluid so I don't think it's that. But I was wondering what you guys would think it is and I want to see what you guys would do. Thank you!

 

Have you brake booster checked.

 

Booster is suspect as mentioned above.
Have you ever inspected and adjusted your rear brakes?
If not, you need to do that.

 

Yes that is one of the things I'm going to try!

 

Have the brakes always been crap or is this a recent change? I ask only because XJs 94 and older only have a single diaphragm brake booster, resulting in less braking force than most people are used to, certainly less than any vehicle that isn't eligible for classic tags in most states. If you do find that the brake booster needs replaced, you should seriously consider the dual-diaphragm upgrade...