Originally Posted By: JustinH
Here is what I do. Many of the coolant geeks on here will call me an idiot, but I have never had a coolant related problem, or any gunk in my radiator.
I drain the coolant using the petcok or pull the lower radiator hose.
I fill the system up with hose water, then run the car for a while, then drain again. I repeat this a third time, then I refill with 50/50 Walmart supertech all makes coolant, and distilled water.
The walmart coolant is 7 dollars, there is no need to spend big dollars on coolant unless you have an odd import with a weird coolant spec.
I do this once every fall, total cost is under 10 dollars.
For my '94 LS400 I use T-Flush with garden hose and radiator petcock open, it took only 2-3 minutes to flush out all old coolant.
Turn off water and let radiator petcock open for a couple minutes to drain as much water out as possible.
With the radiator petcock still open I start to pour in concentrate Prestone/Peak all makes/all models via the T-flush, after a gallon had been in I close the radiator petcock and add coolant until full to make 50-50 coolant-water.
I flush my coolant every 2-3 years, the car is more than 230k miles now and has no problem with over heat, leaking ... Thermostat, water pump, upper hose and some heater hoses had been changed once, but that was expected. Those items do not lasted forever.