Thermostat Replacement

Time to install: 60 mins

Tools Required: Socket set, gasket scraper, RTV Silicon, antifreeze, Phillips Head Screwdriver, Rhino Ramps or Jackstands (to raise the car and drain old coolant).

Under most circumstances, a 180 degree thermostat is fine. Click here to view a video that compares a standard and "performance" thermostat, the results are interesting.

After your coolant is drained, unclamp the upper radiator hose from the thermostat housing. Remove one bolt on top, and the single nut on the bottom with a 10mm socket or wrench. The housing may be stuck on, a few quick taps with a mallet may loosen it.

Yuck, mine had a lot of rust. Yours should NOT look like this! I'll have to do a few flushes. Anyway, you should be able to just pop out the thermostat. Notice how it's oriented, with a small hole at the top of the thermostat and a small pin in it. That's called the jiggle pin, and is used to help get air out of the system.

On the top and bottom of the housing, Take a scraper or blade to remove all of the old gasket. It needs to be smooth so the new gasket gets a good seal. Be careful, scraping and damaging the metal surfaces can introduce gouges that allow coolant to leak out! I stuffed a rag in the bottom of the housing to keep pieces and bits from entering the engine.

Surfaces all smoothed out, put in the new thermostat, jiggle pin at the top!

Well, the Mazda manual doesn't say that silicon is needed, but the guy at the auto parts store recommended it, as does Geoff Kim in his tutorial for the 1st Generation Miata. So I put a very thin layer on between the top housing and the gasket.

Put it back together. Mazda manual states 15-22 ft-lbs for the nut and bolt to tighten it back together. Once everything is back in order drive around when the car is fully warmed, and then check for leaks.