Question about bleeding both coolant circuits on a 2020 GR Supra after a complete coolant drain

[potater1]

I recently drained both the high-temperature and low-temperature coolant circuits on my 2020 GR Supra, so both systems are currently completely empty.

I have the workshop manual and understand that there are two separate bleeding procedures:

1. Low-temperature circuit: ignition on, engine not running, bonnet open.
2. High-temperature/engine circuit: bonnet closed, engine starts and runs the automated bleeding procedure.

My main question is: When both circuits are completely empty, does the order of bleeding matter? Should I bleed the low-temperature circuit first and then the high-temperature circuit, and does one procedure help fill/bleed the other circuit at all?


I also have a question regarding the coolant reservoir caps during the filling and bleeding process. I understand the official procedures specify the cap being closed for the bonnet closed procedure, but it seems like you want it off for the other bleed procedure.

So hypothetically, if the low temp procedure does also bleed the high temp. Should I keep both caps off to see if I need to top off both reservoirs while running?
Since both circuits are completely empty, I want to avoid running either pump dry/mostly air.

Thanks!

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[SJ-Ray]

Start with the low temp one.
Since the engine won't be running you don't need to fear that the high temp one will run dry.

 

[razorlab]

They are completely separate circuits. Do what SJ suggested, low temp one first since the engine won't be running.

 

[rwense]

If you have the tools, definitely vacuum fill first. When I installed my intake manifold it made the whole process easier. I ran the factory bleed procedure three times for good measure and once more at the track after a session and had zero air pockets

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