So I'm about to dig into my new radiator / tranny cooler replacement and I discovered that the previous owner used green coolant. It's nice and neon and I'm not completely concerned that it has green instead of red after all I've researched here...but, at this juncture I want to replace it with Toyota Red.

So, obviously much will drain out of the system when I drain and pull my old radiator...and I'll also pull the reservoir and empty it out.

But, how do I get as full of a flush as I can of the block AND the heater cores (both main and rear seat heater)?

I'd like to get as much of the green completely out of there to make way for the new red stuff. I've done this kind of thing before but never had the need to do a really thorough flush like this.

The only thought I have is maybe do the radiator, add enough coolant to drive it and take it to a shop where they (I believe) can cycle all that through with a machine with heaters on etc.?

Help?

Just put in all distilled water, drive it a day, drain and fill with water only again, then fill with a gallon of red and top it off with distilled.

That is, assuming it won't freeze while you are doing this process.

-Charlie

Don't forget the block drain:

Location of engine block coolant drain plug on '97 V6

I also will be changing back to red after a radiator \ timing belt replacement.

Main concern is removing all the old green coolant from engine and heater cores. Even after a drain and fill with water for a few cycles, seems there would still be some residual diluted green hiding in the block or heater cores. Has anyone used the flush kits that tee into your heater core lines for a more thorough flush?

I would rather not have to do a engine block drain unless totally necessary. After flushing I'm assuming there would be some amount of water in the block and cores. Any idea of how much would remain? Asking the question because I will be refilling with premixed 50/50 Zerex red and am worried the ratio may be way off with a large amount of only water in the system before adding new coolant.

Also I'm assuming I should do this flush process with the old radiator, then remove radiator for timing belt replacement, then install new radiator already having had the system flushed. Right?

Apparently there's barley any left in the block.

You dont even have to drive it for a full day but it is more conveniant that way, after draining and filling with distilled water, just run it for about 10 mins running the heat and when the thermostat opens up the coolant in the core and block will flush...
i bought 5 gallons of distilled water (very cheap) and flushed my system using evapo-rust to get rust out of the block and cooling system, done with the engine running being sure never to let the rad. become empty...I did have to shut it off once or twice to let everything cool down and take a break, but after running 5 gallons of distilled water/evapo rust the coolant was draining clear and then I filled it with prestone EG coolant, didnt use the red stuff...
dont forget to burp the system too
I also used evapo rust and distilled water in the resovoir, let that stuff set in, flushed it with distilled water and cleaned it out as well

Noticed that in the pics of the engine block drain. Any idea how much is left in the heater cores? Wouldn't be as concerned staying with green, but I'm converting back to red after a previous owner.

Just do a couple quick rounds with distilled water, then put in the Toyota Red. You'll see how clear the water is through this process and you can have confidence that there won't be any issues with mixing. I've done it on multiple Toyotas by now with no hints of problems.

-Charlie

Good advice to do two drain/fills with distilled water before changing to your final coolant fill. Just make sure to keep both front and back heater levers on full hot and you'll get complete flushing.

My guess is you'd only have at most a percent of the old stuff left after that procedure. Fresh coolant has chemical buffering (don't ask me how that works, I have no idea) that can more than compensate for any trace amounts of leftover.