Your brakes are bad. Just yankin’ your chain. Could be any thing from no brake fluid to bad brake cylinders to a broken brake line. From the pictures it looks like it has normal hydraulic brakes, not air brakes.

How are you going to get this beast home?

__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine