Mazda MX-5 Repair: Lazy Thermostat

People say that the Mazda Miata is a cheap car to own and maintain. It is not. Ford Crown Victoria was a cheap car to own and maintain. I should know, I’ve had ten of them. In fact I have replaced a thermostat on a Crown Vic, a few times. I even went for the cooler 195 degree option. Between going to the store to pick up the $7 part, removing the two bolts on top / front part of the engine, and dropping the new one in. It would take no more than 20 minutes for the whole process, including the drive to the local parts store.

With the Miata this process is slightly longer.

mazda-roadster-eunos-mx-5-miata

I bought the car in December, just days before my trip to Portugal to marshal the Maxi Endurance 32 hour race at the Algarve Circuit. Before I could even make it home in my newly purchased car from central Long Island I got the Check Engine light illuminated. So I rerouted to the nearest AutoZone store to see what was going on. Code P0126: low coolant level. Hmm!

So I quickly researched the solution to this code on Miata.net and based on the recommendations of people there, rushed out to the nearest Advance Auto Parts store to pick up a new Stant 48728 thermostat. This one listed for about $31 plus tax. Hmm! I used one of the deep discounts Advance always offers, picked up a pair of Mechanix orange gloves with my order, and the box sat on my desk at home for several months, as the Check Engine light went on and off with about five or six cycles of the engine start/use of the car. Admittedly I didn’t use the car too frequently because of the snow/ice situation this winter, so it didn’t get too many miles put on it with the lazy thermostat. But the jist of the problem is the fact that the thermostat gets stuck open, and it takes a while for it to close, at which point the system checks out when you turn the ignition key and the CEL goes off.

With further research from Miata.net it was deemed that replacing the thermostat is not your 20 minute job like with a Crown Vic. This was more a two or three hour affair requiring the removal of a bunch of parts and trying to thread your tools through a variety of tubing just to get to the thermostat on the lower part of the engine, under the throttle body. People recommended to clean the throttle body in this process, why not? It’s already off. Might as well replace the air filter with all that access. People were also recommending to replace the overflow coolant reservoir, because unlike the thermostat which triggers the check engine light, coolant tanks experience catastrophic failure without any warning…. other than an explosion under the hood with the smell and steam from spraying antifreeze. So I ordered the overflow tank, for another $50 + $8 shipping from TASCA Parts a Mazda dealership in Rhode Island. Someone mentioned that their local dealership matched the online pricing of their competitors, but with three dealership within 20 mile radius of my house, none would price match. None of them had the part in stock either. It would have to be special ordered, at a full $70+ list fee, plus $14 shipping for expedited delivery. So I swore off the local dealerships and ordered online. Thanks but no thanks: Mazda of Lodi, Ramsey Mazda and Wayne Mazda!

The dealers did have something in stock that I almost bought, FL22 antifreeze/coolant. But at $26 per gallon I thought that was ridiculously expensive compared to $12 or $13 for Crown Vic antifreeze. So I researched a cheaper alternative and Zerex Asian Vehicle Coolant only carried by NAPA Auto Parts came highly recommended, and at $14 a gallon, a lot more reasonable than Mazda OEM FL22 coolant. Zerex is a Valvoline product.

Anyway, fast forward to this morning and before the mail man delivered the coolant reservoir from TASCA, I rushed out the door to pick up some distilled water to do the coolant flush, and realizing that the radiator/engine capacity for coolant is higher than just one Gallon, I bought another bottle of Zerex Asian coolant.

coolant
engine compartment still very dusty, this is how it was when I bought it… part of the reason I like buying cars from private owners, dealers do a great job of cleaning the engine masking any potential problems in the process.

Got home, dad helped me to jack up the car, and provide all the mismatched tools in his collection to get the job done. I wasn’t trying to rush things instead focusing on doing it right the first time. Everything went like clockwork. I noticed that I didn’t actually have to remove the throttle body and could just lift it to the side to get to the thermostat, neither did I have to undo the brace that sits on top of the shock tower. Didn’t drop any bolts into the abyss while removing the thermostat, and before you know it everything was back in place. Remarkably uneventful install. While the car was still jacked up we filled a bit more than a gallon of distilled water, ran the engine for twenty minutes, then flushed that water out and put in the Zetex. Lowered the car, ran the engine at about 2,500 RPM until the heater started blowing hot air out of the vents. And then went for a drive to fill up the car and see how it goes. It goes perfectly! For a brief while the heater started blocking cold again, which was weird, but then it became hot and even extra hot with a little more driving.

Tomorrow I will top off the coolant to the appropriate level, and the car will be ready for my first big Road Trip to Watkins Glen for NASCAR training next weekend.

thermostat

Voilà, c’est fini!