Cooling system flush



Hello, I want to flush my cooling system in my 2001 Jeep Grand Cherokee 4.0L. My manual says to remove the engine block drain plug, I’m having the hardest time finding it. Is it necessary for me to remove this plug? Can’t I just do repeated water-flushes thru the system to get at the old fluid behind this engine plug?



If you can’t find or remove the engine block drain plug, I suggest draining as much coolant as possible, then filling the system with water and running the engine until the thermostat opens. This will allow water to enter and flush the block.

Then drain it again and refill with 50/50 water and antifreeze. I also suggest installing a new thermostat every time you flush the cooling system.


Thanks for the tip. I think I’ll flush the system with water twice and then add my antifreeze back in. Any idea if replacing the thermostat is difficult?


Change the thermostat when engine is cold. Remove the upper radiator hose ( do this after the flush). Remove the thermostat housing (like a 90 degree elbow). There are usually 3 bolts. The housing, by the way, is at the other end of the upper radiator hose (engine side). The thermostat is inside. Enjoy.


[b]If you fill the system with a 50/50 mix of water and anifreeze after flushing with water, you won’t end up with a 50/50 mix in the system… That’s because there’s still pure water in the engine block after flushing.

Instead after flushing, drain as much water out of the cooling system as possible. Now pour pure antifreeze into the system that equals 50% of the capacity of the cooling system. Then fill up the rest with water. You now end up with true 50/50 mix of antifreeze and water.



You said “and then add my antifreeze back in.” I’m just making sure that by “back in” you are not intending to re-use the old antifreeze.


With some vehicles it is easy to just run the engine with the rad drain open and a hose in the fill opening. Just be careful you are not adding cold water to a very hot system.