- My 2011 Elise SC coolant runs at 194° F during steady-state, low-load conditions like cruising at 4,000 rpm. The outside air temperature has no effect on this number. Sitting in stop-and-go traffic at 100° F, the coolant will get up to 208° - 212° F and then cycle a few degrees above and below as the fans turn on and off. Working the engine hard on the track or at high altitude, I’ve seen temperatures as high as 225° F, but only during the high load. The very minute I back off, temps come right down. I do have dual oil coolers, so that is probably relieving some of the load on the water cooling. I’m running a Radium expansion tank and a 1.3 bar radiator cap.
As far as diagnosing your problem, I’d suggest first pursuing a cause that matches your observations regarding temperature. If you haven’t noticed a significant coolant loss, then look elsewhere because a coolant loss so small you can’t detect it is an unlikely cause.
has already suggested one theory that would align with the very rapid temperature rise you’re describing: your cooling system may have air trapped in it and needs to be bled. Sorry, but all the talk about a “waterline” in your cooling system is distracting nonsense. If there is any air in your cooling system, it needs to be removed by bleeding it. After that, your (properly functioning) system will stay full of coolant whether it’s pressurized or not, hot or not, or in any other condition representative of a properly functioning cooling system. And with a full cooling system, there’s no “waterline.”
I have an Airlift system, but I’ve never had to use it to fill/bleed the cooling system on my Elise. After draining all the coolant and flushing the radiator, I fill the cooling system from the expansion tank. When it stops accepting coolant, I start the engine and continue adding coolant until it won’t accept anymore. When pouring the coolant in, I pour it in a slow, laminar flow stream that avoids adding any unnecessary air into the fluid. Then I bleed the block and coolant hose points, top off the coolant, drive it up and down a few steep hills, then check the coolant level. It usually takes about 1/2 cup more and I’m done. That’s it ... works every time.
If you want to use the Airlift for something, remove the rubber adapter and use it with an air chuck to put 15 psi on your cooling system (that’s about one atmosphere, a little less than your OEM radiator cap). It should easily hold that for as long as you want to hold the rubber cone on the tank. If it leaks down quickly, then you probably have a leak you need to chase down before adding coolant. I just did this the other day to find a (big) leak on another vehicle.
Once you have coolant back in the system and it is bled, you should also verify your electric fans are coming on at the appropriate temperatures ... this is a pretty common failure and would also be consistent with the symptoms you are describing.
Your thread started out with asking about the alternator. Having to remove the clam and wrestle with other parts in the way of a repair sucks. I’ve been there with my Lotus and many other cars. I rehabilitated the cooling system in my VW a few years ago and had to remove the headlights, front grill, bumper assembly, forward cross-member and engine mount, the supercharger, the alternator and probably a half-dozen other things I’ve forgotten just to get the radiator out. That shows a complete disregard for any sort of engineering aimed at maintenance ... it doesn’t have to be that way.