Why would your car heater overheat?

I have a 1992 Plymouth Sundance with 130000 miles. 4 cyl, 2.0L It has been well taken care of with regular maintenance between 3k to 5k intervals since I bought it with 58k. The car instantly overheats when turned on. The heat blows frigidly cold air. It has a thermostat that is ~5 months old. The car will shudder and shake and then cut out when left idling or when it over heats. It is not losing coolant, but the car smells like burning antifreeze when you lift the hood. It will also steam and or smoke that escapes from under the hood when you turn it on. 1.) What are the possible diagnoses? 2.) How much will it cost? (Chicago area) 3.) Is it worth spending the money on a rebuilt car that I've had since high school, or should I just give up and buy a newer car? The most common cause of simultaneous engine overheating and no heat from the heater is extremely low engine coolant level, in other Words a large pocket of air in the system. In some cars it's fairly easy to get the air out, in others it's very tricky. If there's a leak causing coolant loss, that will also have to be addressed or the problem will recur/worsen. Check 1. Your Thermostat (70%) of the time it is your thermostat. 2. Check and see if your radiator is clogged (Also very common).

Another issue is if your car overheats during idle, then it could be the electric radiator fan.

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