Thursday, May 7, 2009

Replacing thermostat on 2000 Mazda 626

Recently my coolant temperature has been going beyond the max limits and my coolant has been evaporating, engine check light came on . If I switch off the AC and turn the heater on, then the temperature reduces but far away from normal. I bought a thermostat, necessary tools and repaired my vehicle as stated below.

  • Locate the radiator, coolant hose coming from the below of the radiator to the engine and air filter.

  • Remove the electrical connections closer to the air filter.
  • Unbolt the nuts of the air filter, Disconnect the air filter from the engine,removing the air filter gives space for easy removal of thermostat.
  • Disconnect the radiator hose coming from the radiator to the inlet of the engine, you would be needing a bowl or bucket to avoid coolant being spilled onto the floor.
  • There is a small steel pipe which connects the radiator hose and the thermostat housing, this steel pipe is attached to the engine housing with two 12mm bolts. These 2 bolts needs to be removed.
  • Thermostat housing comes with two 12mm bolts, thermostat could be located once the thermostat housing is removed.
  • Remove the old thermostat, replace it with a new one, ensure the seals are placed on the thermostat and the thermostat housing.
  • Reassemble all the parts as per the list, fill up the coolant tank with enough coolant to compensate the loss of coolant.
  • Start the engine and notice if the coolant temperature is showing as normal.

Reset the car computer to clear the engine light on, I got this done through Jiffy lubes. I have more pictures to show component's in detail. Mail me and I can explain more in detail.


  1. If turning on the heater returns the temp to normal, the thermostat is not your problem. Check that your electric cooling fans are coming on when the A/C is on.

    Many Mazda engines also have a bleed valve to insure that air is not trapped in the cooling system.

  2. Yes electric fans are coming on, turning on the heater enables the heated liquid to move, hence reducing the temperature. My car had about 100k miles, replacing the thermostat fixed the problem.

  3. Thank you, This has been an ongoing job for me helping people either online or in person.

  4. I am having overheating problems on my mazda 626 - 4 cyl 2001. I replaced the radiator for a new one but my car is still overheating. The coolant/antifreeze water is dissipating so quickly. I also checked the radiator FANs and they are working fine. Somebody told me to check the thermostast but I am not sure if this is the problem with...
    Help please.. I appreaciate it.

  5. I have a 2000 Mazda 626 2.5 engine that is overheating. I have replaced the thermostat, had head work done, replaced the radiator and cap, put in new double fans, replaced two sensors and my car is still overheating. After reading up on all this could my problem be as simple as a couple of bad fuses under the hood? Cecil