Brake Hoses, Lines/piping, And Fittings problems of the 2003 Jeep Wrangler

Airbag cover plastic on steering wheel was breaking down. The plastic became very sticky, as if someone poured a soda on it. It would not clean off with cleaners or plastic preservers. I was not confident it would work as designed if airbag deployed so I bought new airbag unit for the steering wheel. Parking brake will not hold vehicle on minor grade. It always worked until the last 2-3 years. I have had it adjusted, the cables replaced, and the brake pads replaced. It does not matter whether my brake pads are new or old. If I do not park the vehicle with the manual transmission in gear, it will move on its own, or if it does not roll backwards, it will, if any light force is applied to it. I had to install install a hydraulic brake line lock on the rear brakes to make sure my vehicle will not move on a grade I know it is an 'old' vehicle, but I like it a lot, it is well maintained and looks new. It is mechanically simple to and inexpensive to maintain. However I should not be having to buy things like airbags who's plastic degrades. I and my mechanic have no idea why the parking brake stopped working as it had before. He is a master mechanic and an expert machinist.