Hi y’all, I know there are already a lot of threads about this, and I’ve read through many of them, but I’m still pretty confused about what’s going on with my S.

I bought my S2000 in December, and since I live in Illinois, I haven’t driven it much until recently. Now that the weather’s nicer, I’ve been taking it out more. I recently replaced the OEM radiator and hoses with a Koyo Aluminum Radiator and Mishimoto hoses, and I transferred over the OEM fans and temperature sensor.

After reinstalling everything, I burped the cooling system and took it for a drive around the block, but it started overheating. I let it cool down, burped the system again, and got more air out. Yesterday, I drove it again and it stayed at about 3 bars. I kept driving it—ended up going around 50 miles in about 80°F weather—and had no overheating issues at all.

Today, though, I drove it to work. It was much cooler, around 44°F, and after about 15 minutes the car started overheating. It jumped from 3 bars up to 7 bars pretty quickly, so I pulled over right away and shut it off. Someone picked me up, and they drove the car back. They said it would stay at 3 bars for about 10 minutes, then suddenly jump to 7 again, so they pulled over as well.

I’m just really confused. Yesterday it was hot out and I was driving it harder with no issues. Today it was cooler, I was driving calmly, and it overheated.

If anyone can help point me in the right direction, I’d really appreciate it.

Thanks,
Cole

 

It sounds like you still have air trapped within the coolant system. It took me around 35 minutes at idle (after the engine reached operating temperature) to get all the air out of the system.

The key is if you get hot air out of the vents, minutes after you start the car in the morning — then air bubble are no longer trapped in the system.

Park the car so the front is higher than the rear. This will help remove the trapped air bubbles from the system.

I used the Lisle funnel system.


Good luck!

 

99% chance you still have air in the system.

When it is properly bled, if you hold the RPM up a bit from idle, turn your heat and fan to max and hold the back of your fingers against the vent, it should get uncomfortably hot on the back of your fingers. If not, you have not finished bleeding it.

What is your bleeding process? The Billman coolant bleed process works well. And you can also use the lisle funnel along with it (makes less mess and helps bleed the system). Any coolant bleed funnel will work, Lisle just makes one.

I use a combo process like the below

1) I park with the front wheels on my short race ramps to help out the process
2) I put the bleed funnel on the radiator, fill up the system with the front bleeder (the one near the front of the head) open to push out any air up front. I never use the rear bleeder on the firewall like the shop manual states.
3) Start the car and let it warm up to 3 bars (Ap1. If AP2 the number of bars is different but same process). I hold it at 2000 rpm to speed it up
4) Turn car off, crack front bleeder again slowly until you hear air hissing out. Once air is done coming out and it is just liquid, squeeze the upper radiator hose with your hand (wear gloves or use a rag if too hot) and HOLD it that way as you close the bleeder. Top off radiator (if using a bleed funnel you wont need to top it off)
5) Turn on car, hold at 2000 rpm again and put the back of your hand (fingers curled down so the backs of your knuckles are against the vent) against the vent
6) Unless it gets to the point where you need to move your hand within 2 minutes, then shut it off at 2 minutes and repeat step 4 again and repeat
7) Once the air is very hot, like nearly burning your fingers hot right at the vent, then you are done bleeding. If you did not use a bleed funnel, top it off before driving. If you did use a bleed funnel, just put the plug in it and remove/drain the funnel.

Sometimes if I have good hot air I will let it idle a few more minutes with the bleed funnel on it to make sure no more bubbles come out. Just be careful as this will be boiling temp liquid, so take precautions of course.

If you are not getting air to the point it is that hot, then try this process before troubleshooting further. But a car that is fine and then randomly overheats like you are seeing is many times due to air in the system.

 

Thank you, I appreciate your response and ill give it another go.

 

Thank you, I'm going to keep trying that and see if I can get the air out.