I live in AZ and I just bought a 54k mile 2015 IS350 F sport. I noticed the coolant reservoir only has distilled water in it.

i wanted to flush it but turns out to be difficult than I thought it would be. Is it necessary to flush out from the engine block? Why can’t I just drain it all out from radiator? I thought I can do it myself and according to some people that it’s a PITA to do.

i took it to a mechanic who my friend referred me to that worked on his ISF. He’s charging me $150 for labor but he had no clue on anything about the two drain petcock valves on the engine block and was just going to drain it from the radiator. He also told me to buy 6 Toyota coolant to completely flush it out. After I told him about the drain petcock valves on the engine he was totally clueless and told me it wasn’t necessary. Despite the fact that 6 Toyota coolant will cost me a lot of money plus the labor I’m paying this man. I might as well pay the Lexus dealership to do it at that point.

So do you guys think I’m ok to just flush the radiator?

 

Is it completely filled with water (and are you SURE it’s distilled), or was it just topped up with it?

I also wonder why it was topped up, or was the PO tracking it and using water and water wetter - which in fact cools better than regular coolant. It is in fact possible to get the thing to a healthy degree of coolant with messing with the block drains. They can be tricky and if you mess one up you are in a world of hurt. You friend is correct, it can be done w/o messing w/them given the proper technique.

If I were you, and it’s full of dH20, I would go get two gallons of concentrated AMAM coolant (Peak 10x, for example). Fully compatible w/the car.

- take the spec’d volume of the system - let’s say 10 to make the math work.
- Drain the rad from the lower hose.
- Add the concentrate with the goal of getting 6 of your 8 qts (2 gallons in).

You’re done. You know have a very protective 60/40, which gets 20% more anti-corrosion and anti-wear additives in to the solution vs. 50:50, and you get some minor boiling point elevation protection for your hot climate, but that’s not really major.

Toyota coolant is not magical; there are many compatible alternatives out there, AND: available in concentrate, unlike the Toyota, so you can protect better. It’s win:win with zero downside. All of our vehicles have 60:40 mix of an AMAM coolant, except the 2024 ES UL, which I won’t service until ~2029. And then it will start getting that.