I just got my coolant replaced.
Here are the steps

Tools
10mm Socket Wrench
2 Gallons of Toyota Super Long Life Coolant(this is premixed so NO need to dilute)
Ramps
5/15th Inner Diamerter Vinyl Pipe.(I got mine at Lowes)
A bucket to receive the old coolant.
A crawler to get under the car.
A funnel.

Turn on the engine and set the thermometer high
so the heater is on.

Get the front wheels on a pair of ramps.

Turn off the engine.

Wait/Make sure the engine is cool.
You will be getting very close to the catalytic converter/exhaust pipe
so this is critical.

Open the coolant filler cap.

Get under the car.
Find the drain **** on the engine block.
This is on the passenger side under the
manifold, by the third cylinder exhaust(farthest back).
This is a very tight spot.
Reach in over the suspension A-Arm(wishbone).
Plug in the drain pipe.
Dangle the other end into the bucket.
Use a 10mm socket wrench with a short extension, 2 inches or so.
Put your arm into the area from above the suspension A-Arm.
Twist open the **** with one arm
just enough until the coolant starts to drain.
Half a revolution should do, do not remove the nut.
Wait for 10 mins to drain fully.
Tighten the drain nut.

Now get under the radiator.
Find the drain ****.
Plug in the drain pipe.
Open the drain ****.
This is a white plastic butter fly ****.
Turn until the coolant flows.
Wait for 10 mins to fully drain.
Tighten the drain ****.

Get above the engine.
Remove the front most engine cover.
Press the plastic fasteners
in the center and remove the fasteners.
Remove the two 10 mm bolts
holding the coolant reservoir.
Pull out the cap.
Pull out the reservoir.
Drain the existing coolant from the reservoir.
Replace the reservoir.
Replace the resservoir cap and bolts.

Fill from the fill hole using a funnel.
Go slow.
Allow the coolant to fill slowly.
When full, replace the cap.

Fill the reservoir to the full position.

You should have used almost two gallons
with a little bit left.

Check the reservoir for a few times after the
next few drives. Refill the reservoir if necessary.

Dispose the old coolant at a car parts shop.

Have a beer.

 

Here are the pics

 

One more pic

 

yet another pic

 

Whereever you see ****, the word was "c o c k"
omg, can I not say "drain c o c k"?

 

Just in case there are any 3GS owning toddlers around...

 

Thanks for this! I will try this in a bit. Also, do you know if you can purchase the coolant that you can dilute yourself?

 

LMAO@ Drain the ****! I haven't had my **** drained in awhile, am I doing something wrong? lol

 

hahahahahha

 

Yes you can, but make sure to use distilled water. So the internals do not rust out.

 

Nice write up i need this done as well.
How many miles since it was flushed last and did you see any rust in the antifreeze/coolant.

 

There are drains on both sides of the block.
Heater core is closed while the engine is off.