Whats up guys. I just bought an 87 300TD Turbodiesel Estate with only 150k and 3 owners the second of whom was a Benz mechanic. Beautiful car and it gets me around town without any major issues. It does have a few glitches though which I want to resolve the most major of which is overheating because I want to take it on road trips and use it as a travel car. I am not very knowledgeable about these cars but I really want to learn and get it up to spec. Any advice would be greatly appreciated. Thanks.
PROBLEMS:
1. Overheats when climbing hills on the highway. Driving in town the temp will stay at 90 C and it will usually stay at 90 C even going fast on the highway. When climbing hills going fast on the highway though the temp starts to slowly climb. If I turn the heater blower on full blast this usually drops it down and helps it stay at 90-100 for a while. Eventually though the temp gauge starts climbing again and I have to pull over. The coolant reservoir will be pressed full and boiling and it will usually be leaking out behind the front passenger side wheel which is where the overflow tank drain is I guess. And this happens even when I am not going very fast and in very cold weather. It has a bastard Nissan radiator fan and apparently the original Merc fan works better, but this can’t be the only issue.
2. Rough Startup and starting idle. Revs high and sputters for a few minutes. Valves too tight? Needs valve adjustment? This is during cold temp in Montana winter.

3. Delayed/Hard shift from 1st to 2nd. Jerks. All other gears are fine. Surges at low speed or idle. In 1st gear or reverse rolling slowly or at a stop the engine will rev up to 10 rpm if it is just idling at 5. Might kick up twice while sitting at a red light. Going slowly in reverse this happens a lot.
4. When slowing to a stop the ABS comes on, you can feel it in the brake pedal and it makes its noise.