You Notice Erratic Temperature Changes
If you notice sudden and erratic temperature changes from cold to hot or hot to cold, then it could be a sign that your thermostat has stopped working correctly. Get your vehicle inspected if you notice these extreme temperature changes in your vehicle interior.
Signs of a Bad Thermostat
If there's no change in your home's temperature when you adjust the temperature, or the display is unlit or unresponsive, your thermostat may be broken, or the batteries need replacing.
Due to corrosion or aging, your car's thermostat can get stuck in a closed position. If this happens, the thermostat will not let the coolant reach the radiator, and, as mentioned above, the engine will overheat, causing severe damage. One of the lesser-known issues is the polar opposite of overheating.
A defective water pump cannot be repaired, it must be replaced with a new one. It is a common practice to also replace the vehicle's thermostat when doing a water pump replacement. It is not always needed, but if you suspect that your engine got hot when the water pump failed, it's a good idea to take care of it.
If your thermostat has fresh batteries but suddenly lacks power, flashes, or isn't responsive to adjustments, it may need replacement. If resetting the thermostat doesn't resolve the problem, you may have wiring problems or faulty components causing your thermostat to not turn on.
Standard thermostats: Enlist a friend or family member to assist, Position one person by the thermostat and one person by the furnace. Slowly turn the thermostat from off to heat and increase the temperature. Both the thermostat and furnace should make a sound.
A broken thermostat is more than an annoyance – it could quickly cause your house to get uncomfortably hot or cold, and it often leads to substantial energy waste as well. However, similar problems can occur if the AC unit or furnace has an issue or if the ductwork in your house is leaking.
While there is a small chance that there is an issue with the running temperature of your engine, by far the most common issue with trouble code P0128 is a faulty thermostat. The exact location of the thermostat and issues related to a damaged thermostat may vary depending on your vehicle.
Engine Overheating
The most obvious sign that your radiator is damaged is if your car overheats frequently. If the temperature gauge in your vehicle is rising higher than usual or if the engine warning light comes on, these are both indications that your radiator needs to be checked out.
Temperature Fluctuations: One of the most common signs of a bad thermostat is erratic temperature readings on your dashboard gauge. If you notice that the temperature gauge moves from normal to hot quickly or fluctuates unexpectedly, it's a clear indication that your thermostat may be malfunctioning.
Leaking or residue from the front of the engine, overheating, and whining or squealing noises from the engine can indicate a bad water pump.
Engine Sputtering and Hesitation
If there's water in the fuel, your engine might sputter and hesitate when accelerating. The irregular combustion can make the engine sputter as the engine struggles to maintain a consistent acceleration.
Coolant level sensors report low radiator coolant. Symptoms of a bad coolant level sensor include an illuminated check engine light, an untriggered coolant level sensor, and an overheating engine.
The most obvious sign is your engine overheating. If the thermostat is stuck closed, the coolant can't circulate, causing the engine temperature to rise. A stuck thermostat can cause the coolant to boil over, leading to leaks around the thermostat housing or other parts of the cooling system.
It's not recommended to unplug the coolant temperature sensor unless necessary for diagnostic purposes, as it can adversely affect engine operation and potentially cause damage if left unplugged for an extended period.
Another problem that a carbon dioxide test could possibly reveal is a ruptured cylinder head, which causes similar symptoms to a failed head gasket. In many cases, a cylinder head crack will be too tiny for the human eye to spot, yet it could still be a major problem.
A failing water pump can usually be characterized by coolant coming out of the pump seal orifice or by internal noise - if a pump gets really bad and seizes, your engine will probably stop turning due to belt friction.