One problem related to brake master cylinder has been reported for the 1998 Jeep Grand Cherokee. The most recently reported issues are listed below.
During normal driving down a mountain road, break pedal went to the floor. Attempts make to pump break with no effect. Emergency brake was pulled with no effect. Vehicle slammed into rock wall and then landed into a 10+ foot ravine. Was informed by mechanic the master cylinder failed which caused a near fatal accident with 5 people in the vehicle. I recently found out there was a recall on a replacement master cylinder for that make a model but cannot verify if this was a replacement part or not. I cannot not find any information with casting numbers of effected parts. The recalled master cylinders it reports the part was affected in cold weather but this happened on a warm summer day. The recall I am referring to was initially reported in 2006. All that happened and the airbags did not deploy. I do have pictures of the accident and the master cylinder as well as documentation re the accident reports, I am having a hard time uploading them.