Thermostat Replacement

 

Covers:

Thermostats control the temperature of the engine coolant. This can effect engine operation, performance, and the heating system. If a thermostat is stuck open or opens prematurely, the coolant temperature will stay too cool, affecting the air/fuel ratio as well as the heating system. Symptoms include poor heating by the climate control system. If a thermostat is stuck closed or stays closed past the specified temperature, the engine can overheat, causing poor engine performance and and possible engine damage. Many people unfamiliar with engine maintenance or operation don't know what the thermostat does nor even where it's located. This causes the thermostat to be often overlooked when diagnosing coolant system problems.

 

Changing the thermostat is relatively easy and very inexpensive. Most thermostats cost between $5 and $10. The O-rings usually cost less then $3 each.

 

Overview

The thermostat is located in the thermostat housing and covered by the water inlet housing. The water inlet housing is where the lower radiator hose connects to the engine. DO NOT service the coolant system until the engine cools.

 

Parts Required

Tools Required

Removal

  1. Remove the radiator filler cap (behind the engine oil dip stick). Place a bucket or pan under the radiator drain plug (lower end of radiator, toward passenger side) and drain the coolant (See Image #1, below). A 3/8" hose can be connected to the outlet to direct the coolant during draining.

  2. Replace and hand tighten the radiator drain plug.
  3. Remove the air cleaner intake tube as follows:
    1. Remove the three mounting nuts.
    2. Loosen the clamp between the intake tube and the air cleaner box.
    3. Remove the intake tube from the vehicle.

  4. Remove the clamp from the lower radiator hose at the water pipe and disconnect the hose.

  5. Remove the water pipe mounting bolt and remove the water pipe from the vehicle by pulling it away from the water inlet housing. Disgard the o-ring.

  6. Remove the two bolts from the water inlet housing and remove the housing. It may stick, so light prying may be required, but be careful not to damage the water inlet housing or thermostat housing.

  7. Remove the thermostat from the engine and disgard the o-ring.

  8. Using a scraper or razor blade, carefully clean all the old gasket material from the water inlet housing and the thermostat housing. Make sure the surfaces are clean and smooth to assure proper sealing when reinstalled.

Installation

  1. Place a new thermostat into the thermostat housing. The tab on the thermostat should be at the top and aligned with the recess in the thermostat housing. The side with the spring should be facing the thermostat housing.

  2. Install a new thermostat o-ring.
  3. Install the water inlet housing on the thermostat housing and tighten the two bolts to 14-18 ft/lbs.
  4. Reinstall the water pipe into the water inlet housing using a new o-ring. Reinstall the mounting bolt.
  5. Reconnect the lower radiator hose and replace the clamp.
  6. Reinstall the air cleaner intake tube as follows:
    1. Connect the intake tube to the air cleaner box.
    2. Tighten the clamp between the intake tube and the air cleaner box.
    3. Reinstall the three mounting bolts.
  7. Refill the coolant system with new coolant (50/50 mix of coolant and water) via the radiator filler port (behind the engine oil dip stick).
  8. Set the climate control system to the maximum heating position. With the radiator filler cap removed, start the engine and allow it to idle until the lower radiator hose feels warm (indicating the thermostat has opened).
  9. Check the coolant level at the radiator filler port and add if required.
  10. Shut off the engine and recheck the coolant level at the radiator filler port, adding coolant if required.
  11. Reinstall the radiator filler cap.
  12. Add new coolant (50/50 mix of coolant and water) to the radiator coolant recovery reservoir (behind driver's side headlamp, right of battery). Fill to the 'F' mark on the cap.

Notes

Image #1



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