How to Install a Miata Thermostat
The installation is easy. (forgive me if you know some of this).
Begin with the engine cold.
- Follow the upper radiator hose from the top of the radiator to where
it attaches to the front of the engine. This is the thermostat housing.
- Remove the two bolts (1.6) or bolt and nut (1.8?). You do not have to
disconnect the radiator hose.
- Tap up from under the neck of the housing lightly to disengage the
old thermostat gasket. Remove the housing. You will see the thermostat directly. You will
also note that nasty green fluid will pour out from between the mating surfaces, this is
cool. If the antifreeze has been in there more than two years, it is probably time to
replace it also. While everything is apart, it is very easy to flush the engine and
radiator. Please do not let that green slime antifreeze release itself into the
environment. It tastes very sweet and will poison and kill (very violently) anything that
consumes enough of it. For years we used to "taste" the fluid to see how
concentrated it was. A chemistry professor told me the substance NEVER leaves your body.
It just builds up till there's enough to kill you, then it does. Be Careful.
- LOOK and SEE which way the thermostat is mounted in the engine. The
new one must go in the same way. Remove the old thermostat and launch over your left
shoulder. Loudly proclaim that you are the planet's greatest Miata mechanic, evoking
absolute confidence in yourself. Open 1 (one) bottle of your favorite malt and hops
beverage, and consume exactly one half of its contents in one big gulp. This will prepare
you for step 5.
- Procure one DULL single edge razor blade. Take said blade and proceed
to scrape off the old gasket from both the thermostat housing and the engine. DO NOT gouge
the aluminum, or you will have a leak! This is a time honored practice, this "gasket
scraping". Be sure to clean out the recess for the thermostat. Do not let any pieces
of old gasket fall down into the engine. All of our great mechanic forefathers started by
learning how to scrape gaskets correctly. (If you lived closer, you could swing by here,
and I would provide beer and scrape the gasket for you....I love to scrape gaskets!) When
you are done with the ceremonial scraping, raise the aforementioned refreshment bottle and
empty its bounty into your digestive tract.
NOTE: The next
step deals with very complicated mechanical processes, and I want you to be aware that
there are many different methods to complete many automotive processes. I would hate for
someone to tell you what I said was wrong when it isn't. There are many ways to seal a
gasket. I myself use numerous ways, depending on the condition of the materials being
sealed. Since we were blessed with peel and stick gaskets, we can dispense with the other
time honored practice of smearing gorilla snot lightly over the housing side of the
gasket. All we have to do is Peel-N-Stick our gaskets to the thermostat housing. By now
you are a true pro. Go to the fridge/snowbank (It is Canada, right ) and grab another
bottle of liquid WrenchMeister, find the opener (a screwdriver will do), and down that
- Drop the new thermostat into the recess where the old one came out.
Be sure to orient the new 'stat the same way as the old one. Git yerself some o'dat fine
sealant material, blue silicone. Put a very light coating of this on the gasket that is
attached to the housing. Do not let the silicone get so thick that it is opaque. Spread it
with your finger about as thick as a sheet of very thin paper, that's it. Place the
housing over the top of the 'stat. Then insert the bolts (nut), and torque them down
EVENLY. Do not worry about undertightening, just make them snug, and if it leaks later,
you can always make them a LITTLE tighter. We don't want to strip or crack anything. If
you prepared the surfaces correctly, there should be no problem sealing.
- Fill the system from the radiator cap opening. The procedure for
opening the rad' cap is as follows: Turn one quarter turn counter-clockwise. Push down on
the cap and continue turning counter-clockwise till the cap stops. Lift the cap off and
fill the system with your favorite antifreeze mixture. Mine's 60/40 Prestone/water. Start
the car, let it warm up. If you are watching the level through the filler neck, you will
notice that when the engine reaches operating temperature, the level in the rad' will fall
and the contents will appear very hot. This is the time to fill the system with more
coolant. Wait a few minutes (I wait for the fan to come on) and fill the radiator all the
way up and install the cap. If you have any remaining coolant, put it in the overflow
bottle if it needs it.
Relax, have fun. At least it's not a British car that you HAVE to