1994 E320 Rear brake frozen

Hi, sounds like the problem possibly lies with the parking brake shoes. Theese are hidden within the rear brake disc and operate independently of the footbrake. The trouble with this system is that the parking brake is only used to hold the vehicle when parked so they are not used very often especially with automatic transmissin versions as people tend not to apply the parking brake but just use the 'p' park of the transmission. After a while the parking brake shoes corrode and the friction material parts company with the metal, these parts have nowhere to go and end up jamming inside the disc. To repair this you will need to remove the brake caliper and brake disc ( which may be difficult to remove and require some 'industrial language' ) also the spring clips that hold the brake shoe to the backplate if not corroded and broken are very difficult to remove and more so to refit. Finally make sure everything is well lubricated with a copper grease or brake grease and don't forget to adjust the shoes once fitted.

As fro the gas leak.... ?????

Thank you very much. I will check that out and hopefully that will solve it.