How do I change the coolant in my 1990 Jeep?
YOU'VE GOTTA PULL THE LOWER HOSE OFF YOUR RADIATOR WHEN EMPTY COOLANT GOES IN RESERVOIR
The drain petcocks fill with crud anyways. Replace the wire clamp with a new stainless hose clamp. Flush it out with water a couple of times. When ready to refill, pour in half the coolant volume with straight anti freeze. Fill the rest of the way with distilled water. That way, any water remaining in the block will be added to the 50/50 mix.
Most people forget to open the coolant drain on the block when changing ar flushing their cooling systems. Unfortunately the drain plug on the 4.0 is cleverly hidden under the manifols and can be a bugger to spot. Also, be careful when the engine is hot. Before changing the coolant are you going to run some cooling system cleaner before draining, flushing and refilling the system? As tenspeed intimated, a lot of crud builds up in the system.