I just recently acquired the jeep Cherokee xj. And have been experiencing quite a bit of problems like terrible ac/heat and my engine over heating. Today on my way to school i had the heat running and i was sitting in traffic for about 15min the engine started heating up for what seemed like no reason. So i turned the heat off and switched it to ac which lowered the heat to about 190 on the temp gauge by the time i made it to the parking lot the heat had picked back up to 210 this time the red light flashed check your gauges. Then the jeep let out this ear piercing nosie so i quickly parked and turned off the car and let the hood up. There was a puff of steam coming from the engine that let on for about 10secs then led by some coolant leaking out of its own tube not the engine. I proceed to wait till it cooled down then went to class. To be honest i have no idea what could be causing the heat to pick up like that. I've had the 2nd and 3rd cylinders miss fire but i don't think that's what caused it.

 

What year you have should always be included.
And leaking out of its own tube not the engine?
Not sure what you mean by that.
Overflow tank maybe?

 

What year? And what kind of sound was it making? Metal on metal squeal? A hiss? Or something else? When was the cooling system last serviced? Anything replaced? Are all fan shrouds intact? is the electric fan working? A puff of steam from the engine? Where, exactly? Coolant leaking out of its own tube? You mean the radiator? A misfire in 2 and 3 could be anything. Injectors, wiring, ignition. When was its last tuneup?

I know, lots of questions.

 

First I would question the integrity of your temp gauge or temp sensor. If it only showed 210 but was overheating and leaking and steaming, I would think the temp gauge is juuuuuuust a little off. My XJ RARELY sees 210 even on 90°F+ days in traffic. But my XJ has been meticulously taken care of and is in no way malfunctioning, so I know my coolant system is in top notch shape.

Start with an easy coolant system flush and see if anything changes. Search for coolant system flush and find steps on how to complete an in depth system flush, not just a basic flush. Unless it has been flushed in the last year, then just check the level and color of coolant to see if its still good. You can also test the coolant to see if its still working like it should. But dont ask me how to do that, I've only heard of it, not done it. Something with acidity and also something about using a volt meter with one probe in the coolant and one on the battery... or something like that.
Please feel free to make fun of me if that is a ridiculous suggestion hahahaha....

 

Turning on the AC is supposed to turn on the auxiliary electric fan; this almost certainly is what caused the vehicle to cool down initially. Running the AC compressor puts additional load on the engine, and dumps additional heat into the AC condenser, which is in front of the already-too-hot radiator, and so not helping. But the extra airflow from the electric fan evidently helped. So you know the electric fan works when the AC is on... but the fan should also come on when the vehicle gets too hot. Keeping the heat on and fan on high, along with AC on, should help, since the heater core acts like a mini-radiator.

Was the shriek metallic, or like a steam whistle? It could have been the radiator cap releasing pressure, which conceivably could sound like a steam whistle.

What is your coolant level in the radiator? (check cold- requires removing the radiator cap). The way the plastic expansion tank is supposed to operate is that when the engine warms up, the coolant expands and pressurizes, then the radiator cap lets some liquid coolant escape into the plastic expansion tank. As the coolant cools and contracts, the radiator cap should let the system suck coolant from the expansion tank back into the radiator.

It sounds like your radiator was low on coolant, began overheating and pressurizing, and blew a "slug" of water and steam through the radiator cap vent, into the expansion tank, and out the overflow tube on the tank.

If the radiator is low, you may be lucky and the problem is just way too low coolant. Fill up the radiator, leave cap off, and idle for a bit to circulate coolant and help get any slugs of trapped air up into the radiator and out the cap. You'll probably have to add a bit of coolant once or a few times as air circulates up to the radiator cap opening. But you may have other issues, and overheating until steam blows out may only be a symptom. As RockyMtn96XJ noted, a coolant flush and fill sounds like a really good idea. You'll get to see what your coolant looks like... nice and clean, or orange mud. Low coolant, muddy coolant, bad water pump, and other things could explain both overheating AND poor heat. But several other things could cause poor heat independent of what's going on with main cooling system.

Flush it out good, fill up the radiator and keep it topped off, and see what symptoms persist.

My $0.02. Your results will vary.