I'll second the reverend, and cdelena can back this up. We were at Texas World Speedway this summer and over the course of two days put the cars through their paces in as much as 108 degree temperatures. I was on the track for more than a dozen 20-30 minute sessions and I didn't hear of anyone in an S2K getting overheated even at 130MPH. Of course, I can't say the same about the drivers!

I would have been surprised, honestly, if I had seen an S2K overheat, due to the fact that the cooling system in these cars (along with everything else) is so new. The problems with overheating typically occur after the cooling system has gotten the chance to get gunked up over time and heat transfer through the radiator goes way down.

 

I've never seen more than 3 bars either.

But there is a governer buint into the engine control system. If you try to push the engine before you reach 3 bars, it will not go over 7000 RPM (I think, could have been 6000). Try it next time and you'll see the speed drop when it hits the limit.