First, I was under wrong impression that Toyota RED coolant (the one that needs to be diluted 50/50 with distilled water) lasts some 50k miles. It doesn't. It seems that the official lifespan is 30k miles, or 2 yrs whichever comes first.
The Toyota PINK coolant lasts much longer, I believe 50k miles. That one is bought pre-mixed, and used as-is. No mixing with distilled water.

During the past week I flushed my cooling system. First I drained all the original Toyota red coolant, and it looked relatively nice - almost as good as new. I refilled with distilled water and 1.5 bottle of Prestone radiator flush liquid. Drove like that for a few days, around 100 miles total. Then, yesterday, I drained that and found the water coming out was dark gray! It looked like really bad laundry water. I flushed again with distilled water only which came outt clean and then filled it up with 50-50 Toyota red.

I don't know if that gray dirty water was normal; the only thing I can think of is that when I initially bought the car, the previous owner had that green stuff in the cooling system. I wonder if that started a corrosion that is still going on... or maybe the dirty flush water was normal?

In any case, flush your cooling system even when it seems pristine, and do it with Prestone.

 

1999 LS400 270k miles
i am thinking about getting a new radiator and change a bunch of things at the same time- radiator, timing belt, water pump, fan bracket, tensioner, idler, coolant temperature sensor, thermostat, upper radiator hose is new, will change the lower one.
I have a bottle of chemical for cleaning cooling system, forgetting the brand.
Shall I clean the system Before changing all those components?

 

I would say yes. That way if anything is gunked up, say in the heater core, then none of that would go through your new radiator. You should do what peter did by flushing. Drain, fill with water and flush, drive, drain again, fill with water, drive and drain again. At the last drain is when you should change out all those new parts.

 

A mechanic nephew cleans using dishwasher soap.Swears by it.

 

I doubt it beats Prestone. Prestone is made to neutralize the oxydation that happens in the cooling system, which is pH dependent and the chemicals are geared strictly toward that. I fail to see how a dishwaher soap which is made from enzymes meant to remove fat deposits and such can beat it.

 

He's told me stories of cleaning out systems that are a 'mud' slush.Use the info as you will.

 

Sure, I appreciate your sharing it, just don't think I'd like to experiment with it.

 

I saw this on the internet. It must be true. (actually, I do believe this one)