Coolant problem, need help
 

Hi, I recently bought a 96 jeep cherokee country with 139k miles on it. i noticed the temp gauge wasn't working, but all other gauges work just fine. when i take the cap off to the radiator the color of the fluid is rust colored with some noticeable thin sludge. i figured the coolant temp sensor or the temp sending unit was bad, so i replaced both. however, the gauge still isn't working. today i took my jeep through some mud and when i came home i noticed the coolant was leaking onto the ground, it appeared it was coming from the overflow tube. the engine seemed kind of hot and noticed a slight burning smell. is it possible the coolant just isn't flowing through the system because the radiator is clogged? i just bought a new radiator, i figured the radiator probably needs replacing any how. I'm gunna try replacing the radiator and flushing the whole system to see if that works. but does anyone have any thoughts?

You can test the sending unit (the sensor at the rear of the block) with a lighter. I'd start with the old one.
Turn your key to "on" and hold the lighter to the base and see if the gauge responds. If it does, DO NOT drive the jeep until you've resolved the cooling issues or you'll damage your engine if you haven't already.
Is the coolant leaking from the hose or where it connects to the radiator? I'd replace the hose if you're doing the radiator just to be safe.

Do not forget to reverse flush out the heater core when flushing out the system.

^Yep

If it were me, I’d replace all hoses, water pump, thermostat and delete the heat control valve while I was at it.

Crossed fingers you didn’t damage your engine...

Cheers.