Overheating is the most common symptom of a failing thermostat. 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.
A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.
One thing that can happen that damages the thermostat is it can develop a slow week through a closed valve. If the valve refuses to open, the coolant will eventually seep out of the thermostat and pool around its housing. Unfortunately, because it is a liquid, it will corrode the thermostat housing.
The main symptoms of a failing thermostat are related to engine overheating. It can be easily noticed because the temperature gauge in the vehicle will probably read unusually high. This can be caused by the valves being stuck in a closed position.
Stuck Valve
The most common issue a thermostat valve can have, which will cause it to cease functioning, is it it becomes stuck in the open or closed position. This will cause your engine to either become too hot or too cold, severely affecting the performance of your car.
It could be displaying an inaccurate temperature. In this case, your car may not be overheating, but your temperature gauge won't be able to warn you. Thermostats can often go bad after about 10 years of use.
You can try to clean or knock on a thermostat to get it unstuck. However, that's only a short-term fix you should not rely on. Remember: a stuck thermostat is terrible news for your engine, regardless of whether it's stuck open or closed. So, the best thing you can do is replace your stuck thermostat with a new one.
The average cost of a new thermostat, including installation, ranges in price from $50 to $500 or more based on several factors including the type of thermostat, labor costs, the complexity of the installation, and more.
Generally, repairing a thermostat costs around $200 to $500. This is the price range you'll find for most vehicles, although some may be higher or lower depending on the circumstances. But if we're talking complete replacement, expect the price to increase by $50.
Turn your thermostat to the 'off' position... Then venture off to your home's breaker box. Find the breaker to your HVAC system, flipping it 'off'. Make sure the breaker is flipped all the way 'off,' then wait for 30-seconds. Turn the breaker back 'on.
If your temperature gauge shows a consistently high reading, it could be due to a thermostat that's stuck closed, preventing coolant flow and causing your engine to overheat. Poor Fuel Efficiency: A faulty thermostat can lead to inefficient fuel usage.
The Lifespan of a Thermostat
On average, most thermostats last about 10 years, depending on the model, usage, and proper maintenance. However, many people decide to replace their unit sooner to take advantage of new energy-saving technologies.
A malfunctioning thermostat will have trouble keeping your home's temperature at the right setting. If there's something wrong with the motherboard, it may change its own settings at random. You can test the thermostat by lowering the settings to see if the problem persists.
In most cases, installing a new thermostat is a relatively simple do-it-yourself project that can result in improved comfort and convenience and one that can help you save energy.
As the engine heats up, the thermostat should open up and allow the coolant to flow from the radiator to the engine. If you see the coolant flowing through the radiator, then the thermostat opened and is working properly. If not, then it is most likely stuck closed.
This is an easy problem to solve yourself by simply removing the plastic outer casing and, with a very soft brush, delicately brushing off its coil and contact surfaces. It is most effective to clean the thermostat first at its lowest setting, then again at its highest setting.
If the valve is stuck open, your engine will not get a warm start because the exhaust will be channeled straight out the tailpipes, instead of around the base of the carburetor to warm up the engine. You will find your engine is slow to start and will not stay warm.
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.