Question about 2004 Ford Focus
2004 focus with 2.3l has had two new water pumps, 3 thermostats, two new head temp senors & all new hoses... used NAPA parts first and now motor-craft parts. Keep get engine light with code P0128. Local Ford shop said check alignment of thermostat... I am at the point of disconnecting engine light or trading it off. Any suggestion?
Posted by Anonymous on
Unusual for an engine in good condition and running well to run too cool and not complete a warm-up cycle, almost impossible in fact if the thermostat is sealing properly, except in arctic temperatures, though it is worth noting that switching on the heater fan too soon can considerably slow the warm up.
Sometimes gas bubbles escaping from the cylinder head gasket can't escape through the degassing system congregate in a trap or crevice inside the water jacket, usually the build up of gas is under the thermostat and will cause overheating but sometimes it insulates the temperature sensor fooling the electronics into believing the engine temperature is low.
Failing this possibility it is worth noting a temperature sensor can only be accurate if the circuitry has the correct voltage delivered to it. In these modern times of computer control, at the business end it is more about digital stuff and duty cycles than voltage but the digital circuitry must be delivered the correct voltage in order to work correctly. I suspect the voltage regulation will be buried inside the main ECU.
It is easy-ish to check the degassing system and that the thermostat is functioning correctly and using an infrared thermometer check the engine temperature is exceeding the thermostat opening value. If it is genuinely running cool a radiator mask might be necessary but if the temperature is normal the problem clearly relates to the electronic/electrical system.
Posted on Nov 10, 2017
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Posted on Jan 02, 2017
There seems to be an air pocket or no antifreeze in engine block. Try this method disconnect upper radiator hose and pour water directly into hose down into engine block until it full. when its filled reconnect hose and fill up radiator. as the vehicle warms up open bleeder valve on the thermostat housing and release air from system. open slowly and BE VERY CAREFUL WATER WILL BE HOT, bleed until you get a steady stream opening and cosing valve. However if all of this don't work. You may have a bad pump. Good Luck
Posted on Dec 27, 2008
PO172 means that an oxygen sensor in bank 1 detected a rich condition (too little oxygen in the exhaust). I would replace the thermostat first. The computer could be injecting too much fuel because it thinks it never gets to operating temperature. That may keep the light off.
Posted on Jan 28, 2009
I recommend flushing the radiator thoroughly if not done recently. there seems to be some sort of blockage in the radiator at this time. if you get lots of metal fragments that are flushed out during this flush, i will then recommend a rebuild on the radiator or replacement of the radiator. make sure the cooling fans are cycling on time as well.
Posted on May 21, 2009
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.
Posted on Jan 06, 2010
Did you burp the air out of the system after changing those parts? It sounds like the thermostat isn't opening which is why the lower hose is still cold. Click my screenname, go to my tips and tricks, and choose the one about burping the cooling system - it may help you out.
Posted on Jan 28, 2010
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