who dailies their miata in the winter? I am COLD and it's only November

Dashpot said:

One last thing:

If you have an upsized/aftermarket radiator installed to cope with the supercharger heat, you'll lose more heat there than the motor will generate in chilly temps. Try blocking 1/2 the rad area with a piece of cardboard before swapping out a thermostat. You may only hit thermo opening temp for a very short time before it closes down again if your radiator is oversized for winter. 

As someone with oversized al radiators on multiple Miata - this won't come into effect with a properly working thermostat within any of the temperature ranges discussed here. I've never even seen my exocet "drop below working range" after heated up in ~38* temperatures on track and it's all holes and has an oversized radiator. 

Dashpot said:

One last thing:

If you have an upsized/aftermarket radiator installed to cope with the supercharger heat, you'll lose more heat there than the motor will generate in chilly temps. Try blocking 1/2 the rad area with a piece of cardboard before swapping out a thermostat. You may only hit thermo opening temp for a very short time before it closes down again if your radiator is oversized for winter. 

That won't be a problem if the thermostat is working correctly.  In cold weather, any radiator is massively oversized, especially when you're not beating on the car.  That's why there's a thermostat to limit how much coolant goes to the radiator to be cooled. 

I don't know anything about miatas so take this with a grain of salt. With a cold engine take the radiator cap off. Start the car and let it warm up. Unless the neck is weird you can see when the thermostat opens and the water begins to circulate. If the thermostat is stuck you'll see the water circulate immediately.

Don't block the radiator with carboard. It can get wet and get stuck in the fins. It's not actually cold enough where you are now to ressort to blocking things off. If you aren't warming up, get clean out that stop leak and get a new thermostat. 

I drive ours throughout the winter, but it does have a hardtop, so it is pretty much like any other small car in the winter in regards to cold. But definitely not a snow car without winter tires!

Does that look right to you?

In reply to thedoc :

That's the problem. Should be closed at ambient temperature. It doesn't look like it even can close.

In reply to thedoc :

Lol, that's most definitely broken. Great news! Easy fix.

thedoc said:

Does that look right to you?

lol. Replace thermostat and behold, heat. 

This may have happened when it was overheating last summer. I’ve had bad thermostats before, but this one takes the prize.  I feel like putting it in plastic for a paper weight.

Oh, yes, the heat is now really nice.