2000 Miata starting to overheat

Has it ever had a flush? If not, then it needs it anyway, but it may not be the problem. Overheating can be from a number of reasons. I would check the coolant level first. If it is normal, I would suspect the thermostat, which is another item that should be replaced by 85K miles.

If it is low, I would replace the thermostat, radiator cap, and make sure the coolant reservoir overflow system is properly hooked up. That would be after making certain that there wasn't another obvious leak somewhere else like a pinhole leak in a coolant hose or the radiator itself. If it is leaking internally, it is time to look at the oil for coolant and the coolant for oil, but that is your worst-case scenario.

It could be the fan, it would be unusual at this age and mileage, but not impossible. Is the heating intermittent? Does it go all the way to the red? Does it overheat only at low speeds or at highway speeds as well? Do you have A/C and does this affect the gauge? Finally, are you certain that it is not the temperature gauge or sending unit itself? Someone here can probably point you in the right direction with a few more details.

Pat

Maybe your thermostat or water pump gone wrong. It is recommended to replace it when you do the timing belt change. Check this article.

-j

Your fan is working if the car is staying cool at low speeds. At highway speeds, the faster movement of air through the radiator should be providing adequate airflow to keep the car cool.

Have you checked for any obstructions on the grill and radiator area? The fans provide air from the back, so the symptoms would make sense if something is partially blocking the front airflow through the radiator.

I would still replace the thermostat, it may be going out but is still partially working, and replacing it is cheap and easy. A full coolant flush as well if it has been 2 or more years.

Pat

It's always best to start with the cheap stuff. A new thermostat and a new radiator cap took care of my 1990's intermittent overheating problem. And that was a whole lot less expensive than a new radiator!

Iva & Belle.) '90B Classic Red.) #3 winkin' Miata

95K on my '96. No problems with thermostat, fan motor, nor radiator cap. Had to replace the radiator, though. So any of the former may be more likely, but don't be surprised if it's the latter.

While I might replace a radiator that has plastic tanks--(because every one I've had has failed with a split in the plastic) A simple removal and good flush should have cured the problem with the radiator. If the radiator was previously repaired, the shop may have used the wrong black paint, and screwed up the heat transfer.

To posting beacause you did:

How is a a good flush going to cure a leaking radiator?

The original poster has a cooling problem, not a leak.

"The coolant level hasn't dropped. The temp goes midway between the half way mark to the off the scale mark and only above 80 mph especially with the a/c on. It will stay cool all day if you just putt around."