Alright, I need some talking into this one, I just don't WANT to do it, but I'm almost positive that's what it is. No leaks, no bad coolant seals, no nothin, just starts to overheat unless I run with the heater on, radiator's clear and no debris are stuck in it, clutch fan is ok. Someone convince me this is my problem

 

You got a bad water pump. But its cheaper to change the thermostat first.

Did I appeal to your pocket?

 

Hah, I do have a spare waterpump, so that's no big deal.

 

Just do it and ask why later.

 

Hah, I'm almost positive that's what's wrong, I'm just not in the mood to swap it, and need some talking into to do it

 

Replacing your thermostat will make you more attractive to the opposite sex, make you more intelligent and convince your boss you need a raise.

Did that work?

Seriously, thermostats are a common cause of overheating (and overcooling) problems, and it's a cheap, easy job to replace it. Eliminate the easily fixed problems first instead of tackling the difficult stuff unnecessarily. Even if it's not the problem, you know it won't give you trouble later.

 

It's much cheaper to replace the thermostat then the engine. Less work, too.

 

Alright, NZ wins Haven't replaced a FC thermostat yet, am I gonna get coolant everywhere if i don't drain it?

 

No, you will get a little bit, what is left trapped in the filler neck, but its not a whole lot. Seriosly, the thermostat costs a few dollars and take a whole 5 min to replace, so why not? Make sure you get a OEM Mazda one though

 

And the jiggly thing should be as far up as possible. People have told me it goes all the way up at 12 o'clock, but i've never been able to get it to fit higher than about 2:00.

 

Correct, the jiggalin-pin should be as close to 12 o'clock as you can get it.