Coolant Flush on a TJ
Run engine till thermostat opens and circulates thru system. (CAUTION with hot fluid) Remove the freeze plug (cylinder drain plug) if you want to do it right. Also, you need to carefully loosen the plug on the bottom side of the radiator. Flush the system with lots of water from say the garden hose. Some will tell you to siphon the fluid out of the overflow container also.... When the system is throughly flushed, drained and drains closed, fill the radiator with distilled water and radiator fluid. Also available is a premix that has 50/50 radiator fluid with water.
IF you cannot get the plug out or radiator drain open, just buy yourself a Prestone flush kit or similar kit which has a plastic one way valve that goes on the radiator cap location and you hook your hose to it and flush the system. Using this quasi closed system method is an alternative to pulling the cylinder drain plugs. Caution use your garden hose with little pressure as a garden hose has pressure enough to damage a radiator. Flush the system with lots of water. Some will tell you to siphon the fluid out of the overflow container also. When the system is throughly flushed, drained and drains closed, fill the radiator with distilled water and radiator fluid. Also available is a premix that has 50/50 radiator fluid with water.
..Makes NO sense to try and flush a radiator with a couple of gallons of distilled water as proper flushing takes lots of fluid and some pressure.
When you flush with regular water very little regular water will remain in the block. More important then that little bit of regular water left behind is the fact that you did a very good flush with LOTS of water. This water helps break loose sludge, etc.. For best results they have a fluid you can buy that you use with the flush water.
By the way, radiator flushs with a machine at a local shop are quite effective and inexpensive these days as I mentioned earlier. Another bigge with having a shop do your flush with a machine is you do not have to worry about getting into it with local environmental police, etc. that will ticket you if they see you flushing a radiator into storm drains, etc
Hint: To avoid air pockets in the cooling system have your engine running when you add the last few quarts of fluid into the system.. When you fill a radiator you put the fluid in the opening at the top of the radiator (radiator cap) NOT into the overflow bottle!