I bought my '03 S2000 new and just cleared 10k miles. It still has the original green coolant in it, so it's time (really past time) that I change it out. From what I've read, I need to go with the Honda blue Type 2 coolant, but what hoses should I change? I figure that I need to replace the upper and lower radiator hoses, but what others would it be advisable to do at the same time?

 

Would check lower rad hose clamp as they rust away

 

you bought it new and it has green coolant in it? it should have never had green in it. they stopped doin green in the 90's. any who you can replace the hoses if you like but I honestly would just check the clamps, and give the hoses a feel to see if they have become too soft or hard.

 

thermostat
heater core hoses
wouldnt hurt to change all those mini coolant lines that run near the intake manifold and throttle cable

Id flush it twice or three times to get all nasty prestone coolant out of there

 

It's definitely green and is the original coolant. I bought the car new and literally nobody else has ever worked on the car except one guy who changed the tires.

 

Maybe someone topped off your coolant at some point with the green stuff? As everyone said it would be blue if it were original.

 

100% it came that way and nobody else has worked on my S2000. The information you have about it being blue is incorrect. Below is a thread where others confirm that the coolant was originally green. I don't know when they changed over to blue.
What Color Is The Coolant That Originally Came In Your Car? - S2KI Honda S2000 Forums

 

I stand corrected! Thank you.

 

If you think time vs mileage is more important your 2003 Honda S2000 is long overdue for a coolant replacement. The interval varies depending on the source but no more than 10 years that I can see which was back in 2013. Especially with the green coolant which apparently has a shorter service life than the latest Blue Type 2.

First mileage coolant change isn't due until 45,000 miles, or 35,000 more miles.

I'm not convinced that the antifreeze goes sour just in the engine but it's cheap and easy to change.

-- Chuck