Toyota Celica, Corolla, ECHO & MR2 1999-05

Removal & Installation

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The thermostat is located in the water inlet housing that is connected to the lower radiator hose.

The thermostat is equipped with a by-pass valve. If the engine tends to overheat, removal of the thermostat would cause a decrease in cooling system efficiency.


CAUTION
NEVER drain coolant directly onto the ground! NEVER open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.



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Fig. The oil filter must be removed to access the thermostat on the 5S-FE engine

  1. Position a suitable drain pan under the radiator drain cock and drain the cooling system.
  2.  
  3. On the 7A-FE engine disconnect the engine coolant temperature switch harness from the water inlet housing.
  4.  



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Fig. Disconnect the engine coolant temperature switch wiring located on the side of the thermostat housing

  1. Remove the oil filter on 5S-FE engines.
  2.  
  3. Loosen the hose clamp and disconnect the lower radiator hose from the water inlet housing.
  4.  



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Fig. Loosen the radiator hose clamp ...



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Fig. ... then slide the hose off the thermostat housing

  1. Remove the two nuts from the water inlet housing and remove the housing from the water pump studs.
  2.  



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Fig. Only two nuts hold the housing to the cylinder head



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Fig. Pull the housing straight out to remove

  1. Remove the thermostat and rubber O-ring gasket from the water inlet housing.
  2.  



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Fig. Then pull the thermostat and gasket out



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Fig. Sometimes the gasket is stuck and has to be pried out of the head

To install:

  1. Make sure all the gasket surfaces are clean. Clean the inside of the inlet housing and the radiator hose connection with a rag.
  2.  
  3. Install the new rubber O-ring gasket onto the thermostat. On 5S-FE engines, align the jiggle valve with the upper side of the stud bolt. Insert the thermostat into the housing.
  4.  



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Fig. Only use the correct temperature range thermostat when for replacement



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Fig. Align the jiggle valve within a 10°gap of the stud bolt-7A-FE engine



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Fig. Align the jiggle valve within a 5°gap of the stud bolt-5S-FE engine

  1. Position the water inlet housing with the thermostat over the studs on the water pump and install the two nuts. Tighten the two nuts to 78-82 inch lbs. (9-10 Nm).
  2.  

Don't forget to install a new O-ring onto the water inlet pipe. Apply soapy water to the O-ring prior to installation.

  1. Connect the lower radiator hose to the inlet housing and install the hose clamp.
  2.  
  3. Attach the water temperature switch connector.
  4.  
  5. Install the oil filter and check the oil level if removed.
  6.  
  7. Fill the cooling system with a good brand of ethylene glycol based coolant.
  8.  
  9. Start the engine and inspect for leaks.
  10.  

  1. Remove the right hand cover under the engine.
  2.  
  3. Drain the engine coolant.
  4.  
  5. Remove the fan and generator V belt.
  6.  
  7. Remove the generator assembly
  8.  
  9. Remove the water inlet via the two nuts.
  10.  
  11. Remove the thermostat.
  12.  

To install:

  1. Install a new gasket onto the thermostat.
  2.  
  3. Install the thermostat with the jiggle valve upward. It can be set within 10 degrees on either side of the prescribed position.
  4.  
  5. Install the water inlet via the two nuts. Torque to 8 ft. lbs. (11 Nm).
  6.  
  7. Install the generator assembly.
  8.  
  9. Add engine coolant.
  10.  
  11. Inspect for leaks.
  12.  
  13. Replace the cover under the engine.
  14.  

 
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