Check Engine Light

[Stone17]

My Check Engine Light is on in my 03 Lincoln Town Car.
I got the code scanned and it is for engine thermostat.
Is that right?

How easy is it to change?

[Dereck]

Hi Stone17

What is the code?

If it is P0118 then it is more likey it's the coolant temperature sensor.

Regards

Dereck

[ABE]

The thermostat is very easy to replace. Here is the procedure for a '01, which should be the same as yours:
"Thermostat

Removal and Installation

1. Drain the coolant below the water thermostat (8575). For additional information, refer to «Cooling System Draining, Filling and Bleeding» in this section.

2. Remove the engine appearance cover.

3. Remove the bolts, the water outlet adapter and hose and position out of the way.

4. Remove the water thermostat and the O-ring seal from the intake manifold (9424).

Inspect the O-ring seal, install a new seal if necessary.

5. To install, reverse the removal procedure."

Note the torque setting for the mounting bolts is 18 ft lbs. I think the thermostat mounting bolts are very long and go through the intake and into the head. The lower threads can get corroded and stubborn to remove so work them out carefully. Use some penetrating fluid and alternately loosen and tighten to free up any corrosion.

The reason Dereck is asking for the DTC code is that there are so many of them that relate to an engine temperature issue. Here are some examples:

1. There are 3 codes related to the thermostat operation: P0125, P0126 and P0128. These tend to show the thermostat stuck open and the PCM detects the low ect (engine coolant temperature) sensor readings as problematic. Temperature gauge may show low readings.

2. There are 5 codes related to problems with the engine coolant temperature sensor: P0115, P0116, P0117, P0118, P0119. These codes relate to PCM self testing the ect sensor and finding a problem. Temperature gauge may show no readings, since the PCM provides engine temperature info (from ect sensor) to the gauge for display.

3. Ford also have specific codes: P1116, P1117. And there may be a number of codes that I have missed.

The code descriptor can be looked up in a table provided you know the DTC code. Without the code, diagnosis is very difficult. Very few people can document the exact descriptor.

Hope this helps.

[ABE]

I should have added the coolant fill procedure to the thermostat replacement procedure:
"
1. Remove the thermostat. For additional information, refer to «Thermostat» in this section.

2. Disconnect the heater core coolant supply hose from the fitting at the rear of the manifold.

3. Add the coolant/water mixture through the thermostat opening until coolant appears at the heater core coolant supply outlet fitting at the rear of the manifold.

4. Install the heater hose, using an appropriately sized worm style clamp in place of the constant tension clamp.

5. Reinstall the thermostat gasket (O-ring) and the thermostat. For additional information, refer to «Thermostat» in this section.

6. Add the corect engine coolant mixture to the degas botle until the coolant level is between the "COOLANT FILL LEVEL" marks.

7. Select the maximum heater temperature and blower motor speed settings. Position the control to discharge air at the A/C vents in the instrument panel.

8. Run the engine until it reaches operating temperature.

9. CAUTION:
If air discharge remains cool and the engine coolant temperature gauge does not move, the engine coolant level is low in the engine and must be filled. Stop the engine, allow it to cool and fill the cooling system.

Add the correct engine coolant mixture to the degas bottle until the coolant level is between the "COOLANT FILL LEVEL" marks.

10. Repeat steps 7 through 9 until the engine coolant mixture is between the "COOLANT FILL LEVEL" marks on the degas bottle. Turn off the engine and allow it to cool.

11. Check the freeze protection of the engine coolant mixture with Fluid Tester 014-R1060 or equivalent. Adjust freezing point range if necessary. For additional information, refer to «Engine Cooling» in this section."

[Stone17]

Hi Stone17

What is the code?

If it is P0118 then it is more likey it's the coolant temperature sensor.

Regards

Dereck

Here the code P1028

[Stone17]

I found this.

This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125

In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.

[Dereck]

Hi Stone17

Do you mean P0128 or P1288, my first check would be to test the resistance of the CHT (Cylinder Head Temperature) sensor and the ECT (Engine Coolant Temperature) sensor, also check the sensor connectors for corrosion.

Regards

Dereck

[Stone17]

I cleared the code.
If the code come back I will look into it.

I mean P0128.
Sorry about that.

[ksurf_k]

Hi Stone17

Do you mean P0128 or P1288, my first check would be to test the resistance of the CHT (Cylinder Head Temperature) sensor and the ECT (Engine Coolant Temperature) sensor, also check the sensor connectors for corrosion.

Regards

Dereck

this is also what i would do, very good advice right here!

[ABE]

An alternative approach is to check for a thermostat that is sticking open a little. Two checks:

1. The PCM reads the ECT sensor and uses it for its calculations and also to display the engine coolant temperature on the gauge, so monitor the gauge for lower than normal readings. My gauge shows normal temperature in the center of the gauge, exactly half way up the white pictograph.

2. Monitor the top rad hose temperature as the engine warms up from cold. The small hole in the thermostat top will allow only a very small amount of coolant into the top rad hose, and it will not migrate to the rad. When the thermostat opens there will be a rush of hot coolant to the rad. If your top rad hose gets progressively warmer, especially close to the rad then you have a partially open thermostat. Usually one side mounting fails and the unit twists and will not close fully.

Just another point of view that is easy to check.

[dickwells]

Shouldn't you be able to just observe the temperature guage on the dash and see if it is getting up to operating temperature or not? Maybe the later ones don't have a guage like my 94.

[ABE]

Shouldn't you be able to just observe the temperature guage on the dash and see if it is getting up to operating temperature or not? Maybe the later ones don't have a guage like my 94.
I think your '94 has 2 sensors, one for the gauge and one for the "PCM". The '03 has one sensor that supplies the info to the PCM which then updates the gauge.

Test 1 would do as you say, but is based upon the same info as the PCM has when it generates the P0128 code. Test 2 would also work and is independent of test 1 and the PCM, and for checking purposes gives an alternate view.

The owner can choose the test that suits him/her since neither require test equipment or much knowledge of the location of components.