1998 Ford Escort Diagnose a Bad Thermostat

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The thermostat in your 1998 Ford Escort controls coolant flow to help the engine operate at a predetermined temperature. It is common for coolant thermostats to get stuck open or closed after years of service. However, if you suspect the thermostat in your Escort has failed, you need to diagnose the problem before it leads to serious engine damage. You can do the job yourself in a few minutes to save time and money.

Tools Used[edit]

Large dial kitchen thermometer (if necessary)
Small drain pan
Phillips screwdriver
Short ratchet extension
Needle-nose pliers

Diagnose a Bad Thermostat[edit]

  • Open the hood. Make sure the engine is cool, then remove the radiator cap.
  • Start the engine and let it idle. Walk around to the front of your Escort and watch the coolant through the radiator neck. The coolant should not flow. If you see the coolant flowing, go to step 5.
  • Wait about 15 or 20 minutes to let the engine warm up. Once it reaches operating temperature, you should see the coolant beginning to flow through the radiator neck. This means the thermostat is working properly. If not, go on to the next step.
  • Check the engine temperature by placing a large dial kitchen thermometer on the cylinder head next to the thermostat housing, which the upper radiator hose connects to on the engine side. Check the temperature on the thermostat housing itself, next to the upper radiator hose. These two temperatures should be close to each other. If not, the thermostat in your Escort is not opening. Turn off the engine.
  • Wait about 20 minutes for the engine to cool down, if necessary. Place a small drain pan under the radiator. Open the radiator drain plug at the bottom and remove about two quarts of coolant to bring the level bellow the thermostat.
  • Detach the negative (black) battery cable with a wrench.
  • Remove the air intake tube to gain better access to the thermostat housing, using a Phillips screwdriver.
  • Unplug any electrical wires from the thermostat housing and those around it to gain better access to the housing. Label the wires if necessary.
  • Loosen the upper radiator hose clamp at the thermostat housing using a Phillips screwdriver. Detach the hose from the thermostat housing.
  • Unscrew the thermostat housing mounting bolts using a ratchet, short ratchet extension and socket.
  • Lift the thermostat housing off the cylinder head. Remove the thermostat and gasket from the cylinder head.
  • Visually inspect the thermostat. It should be closed. If it is open, replace it.
  • Bring water to a boil in a small kitchen pan on your kitchen stove. Grab the thermostat with a pair of needle-nose pliers and submerge the thermostat in the boiling water. The thermostat should now open. If the thermostat remains closed, replace it.