1999 Toyota Tacoma 2.7 Liter Change the Thermostat

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Replacing the thermostat on your Toyota Tacoma will ensure its coolant system runs smoothly and keeps the engine cool. A properly maintained coolant system will keep your truck running at optimum levels for many miles. The thermostat is located at the end of the top radiator hose and is responsible for opening when the engine gets hot, and releasing coolant in to the motor. The thermostat closes once the motor is cooled down. If your Tacoma starts overheating it may be time to replace the thermostat.

Tools Used[edit]

Crescent wrench
Drain pan
Socket wrench
Socket set
New thermostat
3 gallons coolant

Change the Thermostat[edit]

Removing the Thermostat

  • Open the hood to access the engine compartment. Locate the petcock valve at the bottom of the radiator.
  • Unscrew the petcock valve with a crescent wrench, to drain the coolant out of the radiator. Allow it to drain in to a drain pan large enough to catch up to three gallons of coolant. Close the petcock valve when the radiator stops draining.
  • Locate and follow the top radiator hose to the motor. Loosen the hose clamp with a socket wrench. Pull the hose off the thermostat housing assembly with your hands.
  • Unbolt the thermostat housing with a socket wrench. Slide the housing cover off the assembly once the bolts are loosened and removed.
  • Pull the thermostat out of the assembly. Remember the exact position it was sitting before it was pulled out.
  • Take the old o-ring off with your fingers. (You must replace the o-ring to prevent the possibility of the housing leaking in the future.) Replace with the new o-ring.

Installing the Thermostat

  • Place the new thermostat in the housing. Ensure it is positioned the same as the old thermostat.
  • Bolt the thermostat housing cover back on to the housing with a socket wrench. Tighten both bolts tight to seal the housing.
  • Place the new hose over the inlet pipe. Tighten the hose clamp to secure the hose.
  • Open the radiator cap to add coolant. Add two gallons of coolant to the radiator. Start the truck and allow the engine long run enough to open the thermostat. Add coolant as the fluid level drops. Pour in coolant until the fluid is visible from the neck of the radiator. Apply the radiator cap once the level is full.

Tips & Warnings[edit]

  • You can purchase the new thermostat and the o-ring from any automotive parts store.
  • Do not work on the vehicle while the engine is hot. Allow the engine to cool down.
  • Contact your local recycling center for disposal of the old coolant.