New owner here, there are two different color coolants under my hood. Any idea?

Are you sure the blue one isn't windshield washer fluid?

 

You can't see the windshield washer fluid, tank is buried in the fender well.

By "battery's tank" I'm thinking you mean you mean the reservoir next to brake fluid reservoir? That's the inverter coolant reservoir.

Probably previous owner replaced engine coolant, but not the inverter coolant; the Toyota USA spec is 10 years/100K miles for first engine coolant change, 15 years/150K miles for inverter coolant change. And 5 years/50K miles for both, after first change.

Maybe just buy Toyota Super Long Life coolant, from dealership, keep it simple?

If you don't know the history, maybe best to replace both asap. If the engine was done at 100K it's overdue again, and the wrong stuff. And I wouldn't doubt the inverter coolant's original.

When draining the engine coolant in particular, do your best to get as much out as possible, clear out what's in there. Besides the radiator drain, there's a drain on the engine block as well, round back, towards passenger end ("front" of engine). You could also pull the lowest accessible hose off the exhaust heat recovery system, might get some there.

A 3~4 foot section of 1/4" ID surgical rubber tubing is the bee's knees for draining, in particular the engine block.

Watch @NutzAboutBolts coolant change videos, link in thread pinned at top of 3rd gen maintenance forum.

Attached is relevant Repair Manual info:

 

+1

I got quite a bit there. The full capacity of the heat exchanger and the hoses. I'd guess about 3/4 of a quart.

 

Good to know.

 

Isn't it true that mixing even small amounts of one type of coolant with another causes problems?

When I bought an '89 Supra in 2001, I discovered the previous owner had filled the radiator with green anti-freeze. I was determined to replace it with Toyota Red, which was sold in concentrated form and was supposed to be diluted 50:50 with water. My solution was to hook up a hose to our hot water tank, stick it in the radiator neck, open the drain-cock, start the car and let the water run until what was coming out the bottom was perfectly clear. Toyota SLLC is not the same as Toyota Red, as I discovered recently when I went to change the coolant again on the Supra, but still I would think that even though it is not supposed to be diluted, having a little water mixing with SLLC would be better than mixing some coolant with unknown characteristics. Since we are talking about coolant for the ICE rather than the inverter, I might be tempted to try something like that again, if I were in the OP's position.

 

Yeah protracted water flush followed by achieving 50/50 mix with Toyota Long Life coolant (comes concentrated) is the best course.

It was suggested here, due to unknown amount of residual water after flush, to start refill with just the LLC, put in 50% of system capacity, then switch to water (preferably distilled) for top up.

AFAIK LLC is completely compatible with SLLC, just change interval is shorter, maybe 1/2.

 

Ok, I guess I got hung up on Toyota recommending LLC (aka Red) for cars 2004 and older and SLLC for newer. Now, on doing some more reading, I see you are correct. That makes me feel better. I had some SLLC left over from changing the inverter pump on the Gen 2 Prius and added it to a container of diluted LLC I had used in the Supra, but then after seeing Toyota's recommendation, thought I had ruined both batches. Luckily I didn't throw it away. So you think I could use it in either car?

 

Yeah I think the only diff is the change interval. Play it same and use LLC interval, which IIRC is 1/2. Just in case you need it, 4th gen coolant capacity is in attached.

Interesting, they say nothing about draining the block with 4th gen engine. Maybe block drain eliminated? I've heard nothing much came out, with 3rd gen.

Addendum, seems to be debate regarding LLC vs SLLC. I'm sceptical they're not compatible, but who knows.

SUper Long Life vs. Long Life Coolant - Toyota 120 Platforms Forum

Toyota red long life & pink super long life same? - Bob Is The Oil Guy

It's just a shame you can only get SLLC pre-mixed. (Is this true?) FWIW, in Canada, SLLC is 55/45 mix. Maybe we should bootleg it to Alaskans?