I recently purchased a 1986 300E. Yesterday while in a parking lot, someone backed into me and all of the sudden I had coolant spewing everywhere. It turns out that a previous owner had cut and spliced the hose from the engine to heater core. It popped off at the splice. So I went and bought a new hose and clamps and filled the radiator. Drove home 13 miles no problem. Later on drove 3 miles to the store and all the coolant overflowed out the expasion tank. I filled it back up with water and drove back home with no issues. What gives? How do I prevent this from happening again?