I have 2008 PT Cruiser; getting P0128 code; I've changed thermostat & temperature sensor; I have to fill the anti-freeze container every 2 weeks; temperature hand will not always be at half way point. I need any suggestions I can get. HELP!!!

Replace thermostat. It is stick open causing the engine to run too cold.

Has the system been flushed? Correct temperature thermostat installed? Are you getting flow through the radiator? Rad cap sealing properly and is it the correct one? Are the fans actually coming on? Is the temp sensor working properly? Rad properly filled or still have air trapped inside? Water level correct? Water pump working or seized, leaking?

try topping it up when cold ,sounds like a air lock

Get the code PT cruiser has problems with P0128,If you have that code you will need to get a ECM reflash to correct the condition

Well, I can't give you any specific information regarding your vehicle because you forgot to mention what kind of vehicle you have. (This is kinda important if you really want some help figuring out what is wrong with your car)

The "Generic OBD" of code P0128 is "Coolant Temperature Below Thermostat Regulating Temperature"

The most likely cause is a stuck-open thermostat, however, I have also seen defective Engine Coolant Temperature (ECT) sensors also cause this code.

P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

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.

Symptoms: You will likely not notice any drivability problems other than the MIL illumination.

Causes: A code P0128 may mean that one or more of the following has happened:
* Low engine coolant level
* Leaking or stuck open thermostat
* Faulty cooling fan (running too much)
* Faulty coolant temperature (ECT) sensor
* Faulty intake air temperature (IAT) sensor

Possible Solutions: Past experience indicates that the most likely solution is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:
* Verify coolant strength & level
* Verify proper cooling fan operation (check if it's running more than it should). Replace if necessary.
* Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary.
* Verify proper intake air temperature (IAT) sensor operation, replace if necessary.
* If the above items check out good, replace the thermostat
* If Nissan vehicle, check for Technical Service Bulletins (TSBs), as the ECM may need to be reprogrammed to correct the P0128 code

Hope helps (remember to rate and comment this).

CODE P0128- THERMOSTAT MALFUNCTION. POSSIBLE CAUSES 1. ECT SENSOR IS OUT OF CALIBRATION. 2. CHECK THE OPERATION OF THE THERMOSTAT IT MAY BE STUCK OPEN.3.INSPECT FOR LOW COOLANT LEVEL OR FOR AN INCORRECT COOLANT MIXTURE.

P0300 is a code for multiple misfire. Which could be created to the P0128
P0128 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.
A code P0128 may mean that one or more of the following has happened:

• Low engine coolant level
• Leaking or stuck open thermostat
• Faulty cooling fan (running too much)
• Faulty coolant temperature (ECT) sensor
• Faulty intake air temperature (IAT) sensor

Past experience indicates that the most likely solution is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:

• Verify coolant strength & level
• Verify proper cooling fan operation (check if it's running more than it should). Replace if necessary.
• Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary.
• Verify proper intake air temperature (IAT) sensor operation, replace if necessary.
• If the above items check out good, replace the thermostat

Good luck and hope this helps. keep me posted, be glad to know your car is running 100% again soon.

water pump ,its a plastic impeller and its loose on the shaft ,,,,,had one a while ago exactly the same but the first time i came across this on a saab i done the same as you ,changed everything ,felt a right you know what

Flush rad & change coolant & thermostat. Check operation of rad fan, & make sure it is coming on when engine reaches normal operating temperature. Be sure to bleed air out good when refilling rad/cooling system. Start engine & turn heater on when refilling & let rad fan come on & off at least 2 or 3 times before putting cap back on rad, and refill rad as needed as you do this. then fill return bottle to proper level & see what happens.