A thermostat is an essential component in the car’s cooling system that monitors and regulates the flow of coolant in the entire engine block. You may hear a phrase like ‘the thermostat was stuck open or closed.
When the car engine is running and gets to a specific temperature, the thermostat will be forced to open, enabling the coolant to travel to and from the radiator and keeping the engine at a standard temperature.
In contrast, the coolant keeps recirculating back and forth the engine. In addition to other cooling components, this recirculating process helps the engine work at a standard temperature.
The opening and closing of the thermostat enable your car engine to run at optimum temperature.
In case the thermostat becomes stuck open, there will be a steady flow of coolant to the engine, which will not allow the engine to reach a certain level of heat, resulting in performance issues.
If the reverse is the case, there will be no coolant passage to the radiator for cooling purposes, resulting in engine Overheating. Knowing the symptoms of a bad thermostat will help safeguard the life of the thermostat and engine.
Understanding the Role of the Car Thermostat
The thermostat is a small but crucial component in your car’s cooling system. It regulates the flow of coolant to maintain the engine’s optimal operating temperature.
When the thermostat malfunctions, it can lead to serious engine problems and costly repairs. In this blog post, we’ll explore the signs of a bad car thermostat, how to diagnose the issue, and the importance of timely repairs.
The car thermostat is a valve that controls the flow of coolant between the engine and the radiator. It ensures that the engine warms up quickly and maintains a stable operating temperature.
When the engine is cold, the thermostat stays closed, allowing the engine to reach its optimal temperature faster. Once the engine is warm, the thermostat opens to allow coolant to circulate, preventing overheating.
How does the Thermostat Work?
The car thermostat’s job is to keep the engine’s temperature within its working limits. This small part sits between the engine and radiator, regulating coolant flow between the two parts.
When the thermostat closes, the coolant isn’t able to flow. When it’s open, coolant flows to dissipate heat.
Most car engines from the past few years operate at the same temperature range to ensure maximum performance.
In general, the car engine should be around 195 to 220 degrees Fahrenheit. When it doesn’t run within these temperature guidelines, it’s not operating efficiently.
When coolant is kept from flowing to the radiator, the engine temperature increases rapidly. On the other hand, as the coolant flows into the radiator, heat is quickly dissipated.
The car thermostat operates as a gatekeeper. It’s either allowing or blocking coolant from flowing from the motor into the vehicle’s radiator. It’s the job of the thermostat to read the temperature of the engine and determine if the coolant needs to flow or not.
If the engine is hot, the thermostat opens up and allows the coolant to move. Otherwise, when the engine remains cold, the thermostat stays closed.
What Does a Thermostat Do for Your Car?
The thermostat is a valve that regulates coolant temperature and helps it stay at a certain preset level for optimal engine operation. It is located between the engine and the radiator.
Although a stuck closed thermostat can cause overheating, modern thermostats more often fail by opening too soon or sticking open, which generally causes the engine to run too cool.
Pro Tip: If, in the winter, you notice your engine running cooler than expected and you don’t have good cabin heat, the thermostat is most likely at the root of the problem. Emissions and fuel economy are also negatively impacted by a cold-running engine.
But other than the obvious impact a cold running engine can have on emissions and fuel economy, an engine that runs too cold for too long can begin to develop crankcase sludge even if the oil is changed regularly.
Why is it important to check the thermostat for failure symptoms?
Preventing our vehicle’s thermostat from failing requires taking into account some considerations.
One of these will be to ensure that the coolant is replaced regularly and carefully so that air does not enter the system as this would lead to overheating and/or faulty sensors.
Another factor to consider in preventive maintenance is visual inspection. Dolz recommends inspecting the thermostat at the same time as the water pump and timing belt.
Replacing them in one single operation will ensure that the valves are mounted in the correct position and that necessary fixings are avoided.
Types of Thermostats
Thermostats come in various types, each with its own set of features and functionalities:
- Mechanical Thermostats: These are the traditional dial-based thermostats. They use a bimetallic strip that expands and contracts with temperature changes to activate or deactivate the heating or cooling system.
- Digital Thermostats: These thermostats offer more precise temperature control and often include programmable features to adjust temperatures based on time of day or day of the week.
- Smart Thermostats: These advanced thermostats connect to Wi-Fi and offer remote control, learning capabilities, and integration with other smart home devices. They can learn your temperature preferences and automatically adjust settings for optimal energy efficiency.
Problems A Thermostat Can Experience
The thermostat isn’t a maintenance or wear-related item that requires replacement at any pre-set level.
Instead, it’s usually only replaced if failing, or whenever the water pump is replaced. The main problems a thermostat can experience are being stuck open, stuck closed, or leaking.
#1. Thermostat Stuck Open.
If the thermostat is stuck open, an optimal engine temperature is never going to be reached, and there will be no or little heat available in the passenger compartment, and engine wear can increase.
#2. Thermostat Stuck Closed.
If it’s stuck closed, the engine is going to overheat because coolant isn’t moving to the radiator. Debris or a broken spring in the thermostat could be responsible for it being stuck in either the open or closed position.
#3. Leaking.
Finally, the thermostat housing can fail and begin leaking coolant.
Symptoms of a Bad Thermostat
#1. Overheating Engine.
When the car thermostat remains stuck closed, the hot coolant cannot flow to the radiator. Because the hot fluid cannot be cooled down, it keeps the temperature of the engine up higher than normal.
Coolant needs to make its way to the radiator to be cooled down. Once this occurs, it comes back to the engine and dissipates more of the heat. However, with the stuck thermostat, the coolant remains stagnant, continuing to build up more heat.
If the engine overheats, it can cause serious damage. For example, if you end up with a blown head gasket, you are looking at massive repair bills.
However, an overheating engine isn’t always caused by a bad thermostat. You want to check the coolant levels to ensure you have enough fluid in the system.
It could also be due to a bad water pump or a cooling system leak. Additionally, the radiator could become clogged. Still, the thermostat should be one of the parts you examine.
#2. Trouble Reaching Operating Temperature.
If the opposite were true from the above complaint, the thermostat would be stuck open. When this happens, the coolant is able to flow freely to the radiator.
Without coolant sitting in the engine for an extended period of time, the operating temperature might fail to reach normal limits. Not only will the engine struggle to increase temperature, but it will also have trouble maintaining its range.
When the engine doesn’t get warm enough, it’s going to be less efficient. You might notice that the motor is using more fuel than usual, costing you additional money at the pump. This problem can also lead to premature wear of the engine components.
#3. Temperature Fluctuations.
When the thermostat starts to fail, it might operate erratically. Sometimes, it could be stuck open when it should be closed and vice versa. This malfunction leads to temperature fluctuations in the engine that aren’t normal.
When the thermostat doesn’t fail uniformly, it can create mixed signals. You will notice strange temperature readings, leading you to wonder what is causing the problem. However, a quick check of the thermostat might reveal that this is the culprit.
#4. Heater fluctuations.
The coolant heats up the heater in your car. Therefore, if the thermostat is not doing its job properly to maintain an even temperature in the car’s engine, you may experience temperature fluctuations inside the car from the vents.
If both your temperature gauge and the heat inside the car fluctuate, it is definitely time to check the thermostat.
#5. Possible Leakages & Steam from the engine.
If the thermostat is not working properly, the hot coolant in the engine coolant chamber will find a way to escape because of too high pressure. We all know that hot air rises and that water boils and forms steam when it heats up.
When the coolant heats up, and the pressure gets too high, it can attack the weak points and cause a leak. The coolant is often pressed out of the radiator tank.
Leaks are often straightforward to detect because they are visible and often show up in white steam smoke.
#6. Rising Temperature and Full Expansion Tank.
If the thermostat flap remains closed, no coolant can escape from the radiator. The coolant inside heats up and begins to convert to steam, while the coolant inside the radiator remains unchanged.
So if you see the temperature gauge rise and the radiator tank is filled with water, you most likely have a problem with the thermostat. A rising coolant level can also mean that the car is about to overheat.
#7. Poor Performance.
The thermostat is a critical component designed to ensure that the engine is always running at its optimal temperature. Without it, the engine won’t operate as it should.
When the motor isn’t running right, you are going to notice performance issues. Most notably, the fuel economy is going to suffer as the engine works harder to compensate for the temperature discrepancies.
If the engine is overheating or unable to reach temperature, there could also be increased emissions from the fault. Not only is the bad thermostat putting the engine at risk for failure, but it’s also contributing to a polluted environment.
Causes of a Bad Thermostat
A bad thermostat can be caused by a range of factors, including:
- Wear and tear: Over time, the components of your thermostat can wear out, leading to faulty readings and inconsistent temperatures.
- Corrosion: Corrosion can occur when moisture enters the thermostat, causing damage to the internal components.
- Power surges: Power surges can damage the electronic components of your thermostat, leading to faulty readings and inconsistent temperatures.
- Incorrect installation: If your thermostat was not installed correctly, it can lead to a range of issues, from faulty readings to inconsistent temperatures.
Understanding the potential causes of a bad thermostat can help you identify the root of the problem and take steps to fix it. In the next section, we will explore the steps you can take to troubleshoot and potentially fix a bad thermostat.
How to Diagnose a Faulty Thermostat?
Diagnosing a malfunctioning thermostat is complicated and risky. You have to deal with hot engine components and perform a series of diagnostic steps to identify the issue.
This can be demanding for inexperienced people and is best left to a professional mechanic.
Here’s how they’ll verify a failing car thermostat:
- Monitor the temperature gauge: They’ll start the engine and observe the temperature gauge. If it steadily rises into the normal range (195°F to 220°F), it indicates proper thermostat function. But if they notice rapid overheating, temperature drops, or slow warm-up, it may suggest a stuck or failing thermostat.
- Scan for error codes: They’ll use an OBD-II scanner to check for codes like P0128 (faulty engine coolant temperature).
- Listen for noises: If they hear rumbling or knocking noises from the engine bay, it could indicate the thermostat is stuck closed and restricting coolant flow.
- Feel the radiator hose: Next, they’ll carefully touch the upper radiator hose when the engine is warm:
- If the hose is cold, the thermostat may be stuck closed.
- If it becomes hot too fast, the thermostat may be stuck open.
- Use an infrared thermometer: If they don’t want to touch the hot hose, they’ll aim an infrared thermometer at the thermostat housing to measure the temperature change. If the temperature jump is around 195°F to 220°F, the thermostat may be working, but a delayed reading may point to a failing unit.
- Check for leaks: Inspect the thermostat housing, nearby hoses, and radiator cap for a coolant leak.
NOTE: Another common method a mechanic may follow is submerging the bad thermostat in a boiling pot of water. If the thermostat opens, there’s no issue, but you’ll have to replace it if it stays closed.
How to Fix Bad Thermostat Issues?
Fixing or replacing bad thermostat issues might be a pretty easy job for most DIY lovers, while others don’t know where to start.
I will show you how to replace a bad thermostat in a simple step-by-step process. Before you proceed, you will need some common mechanic tools to carry out this job easily.
Tools Needed
- A wrench
- A socket set
- Screwdriver
- Plastic gasket scrapper
- Pliers
Other things Needed
- New thermostat gasket
- Drain pan
You have to make sure that you’re using the right coolant. Check your vehicle repair manual and see the specified coolant for your car.
Step 1: Park your car: Park your car in a safe place and engage the hand brake.
Step 2: Allow your car to cool: Like I always recommend, when working under your car hood, ensure you allow your car to cool down.
Step 3: Remove battery terminal cables: Ensure you remove your battery terminal cables when working under your hood. However, if your car computer requires programming after removing the battery terminal cables, you may consider leaving the terminal cables in place.
Step 4: Place a Drain pan under your car: You want to place a drain pan under your vehicle and catch the coolant that will escape when you pop off the thermostat.
Step 5: Locate the thermostat housing: The thermostat housing can be easily traced by following the upper radiator hose. However, the housing may be in a different spot in your car.
Step 6: Unbolt the thermostat housing bolts: Usually, the thermostat housing is fastened with two or three 10mm or 12mm bolts. Grab the right socket and break the bolts free, then unfasten the bolts with your hand.
Step 7: Pull off the faulty thermostat: Once you take off the thermostat housing, you easily pull off the faulty thermostat by sliding it back and forth. Some might easily pull off, while some might prove stubborn. If the thermostat proves stubborn in your case, grab your pliers and tap them back and forth so they’ll easily come off.
Step 8: Clean the mounting surface: Take your plastic gasket scraper and scrape off debris or rust on the surface so the new thermostat will not leak after replacement.
Step 9: Install the new thermostat: Ensure you reinstall the thermostat the same way you pull it off. You can check your owner’s booklet to see how to install the thermostat if you lose track of how you pull it off.
Step 10: Tighten the Bolts: Tighten the bolts the same way you take them off. Run the bolts with your hand and torque them down with your wrench.
Step 11: Cross-check your work: Fix other things like the battery terminal cables. Cross-check your work, and add coolant to your reservoir. You can start your engine and examine the thermostat again.
Smart Thermostat Issues: Advanced Troubleshooting Tips for Modern Devices
Smart thermostats bring convenience and advanced features to your home but also come with challenges.
It can be frustrating if you’re facing smart thermostat troubleshooting problems, especially when unsure if the issue is with the thermostat itself or the connected systems.
So, if you’re wondering, “why is my smart thermostat not responding?” we’ll walk through some of the most common problems and how to fix them.
#1. Wi-Fi Connectivity Problems.
- A smart thermostat not working properly can often be traced back to weak or dropped Wi-Fi signals. This causes delayed responses or prevents the thermostat from connecting to its app.
- Solution: Restart your router and check if other devices in your home can connect to the Wi-Fi network. If the thermostat still has trouble connecting, move it closer to the router or install a Wi-Fi extender.
#2. Unresponsive Thermostat Display.
- A frozen or blank display is one of the most common smart thermostat troubleshooting issues. This may be due to a software glitch or a power issue.
- Solution: Perform a reset by holding down the power button (refer to your user manual for the exact steps). If the display remains unresponsive, check the power source to ensure it’s receiving adequate voltage.
#3. Incorrect Temperature Readings.
- If your smart thermostat is not working properly, it will result in incorrect temperature readings, which may be due to interference from heat sources, direct sunlight, or faulty sensors.
- Solution: Ensure the thermostat is installed in a central location away from heat-producing appliances. If the problem persists, run a calibration check through the app settings.
#4. Software Malfunctions and Firmware Issues.
- Why is your smart thermostat not responding? It could be due to outdated firmware or a software glitch. Regular updates ensure the thermostat functions properly and communicates correctly with other smart devices.
- Solution: Check for firmware updates via the thermostat’s app. Make sure the device has a stable Wi-Fi connection during the update process to avoid interruptions.
#5. Geofencing and Smart Features Not Working.
- Some smart thermostats use geofencing to detect your presence and adjust the temperature accordingly. If these features fail, the problem might lie with the app’s settings or location permissions.
- Solution: Verify that location services are enabled for the app and that the thermostat has been permitted on your smartphone. If geofencing is still inconsistent, restart the app and reconfigure the settings.
#6. Integration Issues with Other Smart Devices.
- Smart thermostats often integrate with home automation systems like Amazon Alexa or Google Home. If your thermostat isn’t responding to voice commands or schedules, the issue may be compatibility or setup errors.
- Solution: Re-link the smart thermostat to the voice assistant app, and ensure all devices use the latest software versions. A compatibility check through the manufacturer’s website can also help pinpoint the issue.
#7. Thermostat Keeps Losing Its Schedule.
- If your smart thermostat frequently forgets its programmed settings or resets to default, this is typically due to a power outage or software bug.
- Solution: Check your thermostat’s backup battery or power source. If power is stable, try performing a factory reset and re-entering your schedules.
If you’re still experiencing smart thermostat troubleshooting issues after trying these solutions, it may be time to consult the manufacturer’s support team or a professional technician.
How do I test my thermostat?
See how to tell if the thermostat is bad in a car. There are several ways to know if a car thermostat is working or not. You can tell if a thermostat is working by checking the coolant flow.
- Open the radiator back.
- Turn on the engine and allow it to idle.
- When you start the engine, the thermostat will not allow coolant passage to the radiator because the engine has not heated up. If the thermostat is passing through, you have a stuck open thermostat.
- If there is no coolant passage at first, and even when the car heats up, you have a stuck close thermostat.
Preventive Maintenance Tips for Extending the Life of Your Thermostat
Preventing faulty thermostat symptoms starts with regular care and attention. Regular maintenance can help you avoid sudden issues and keep your HVAC system running smoothly.
If you’ve ever wondered how to prevent a thermostat from going bad, follow this troubleshooting guide and apply these preventive tips to maximize your thermostat’s lifespan.
#1. Clean the Thermostat Regularly.
Dirt and dust buildup can interfere with your thermostat’s sensors, leading to inaccurate readings and erratic temperature control. Clean the exterior and interior components at least once a season.
- How to Do It:
- Turn off the power to your thermostat.
- Gently remove the cover and use a soft, dry brush or compressed air to clean the inside.
- Avoid using water or liquid cleaners, as moisture can damage the electrical components.
#2. Replace the Batteries Annually.
Weak or dead batteries are common culprits behind faulty thermostat symptoms like an unresponsive display or incorrect temperature readings. Replacing batteries at least once a year ensures your thermostat functions properly.
- Tip: Consider adding battery replacement to your seasonal HVAC maintenance checklist to prevent unexpected power failures.
#3. Recalibrate the Thermostat When Necessary.
Over time, your thermostat may become miscalibrated, leading to incorrect temperature readings. Recalibrating it ensures it accurately senses and adjusts to your preferred settings.
- How to Do It:
- Access the calibration settings (refer to the manual for instructions).
- Compare the thermostat’s reading with an accurate room thermometer.
- Adjust accordingly to eliminate any discrepancies.
#4. Ensure Proper Thermostat Placement.
Placement affects your thermostat’s ability to read temperatures accurately. Placing it in direct sunlight, near drafts, or close to heating vents can cause faulty thermostat symptoms.
- Best Placement Tips:
- Install it on an interior wall, away from windows, doors, or direct sunlight.
- Keep it centrally located in a room representing your home’s average temperature.
#5. Perform a Seasonal System Check.
A comprehensive thermostat troubleshooting guide should include routine checks on the entire HVAC system to ensure all components function properly.
- How to Do It:
- Inspect the thermostat’s wiring connections and look for loose or corroded wires.
- Test the HVAC system’s response to changes in temperature settings to confirm the thermostat is communicating correctly.
#6. Protect Your Thermostat from Power Surges.
Power surges can damage the sensitive electronics inside your thermostat, leading to sudden faulty thermostat symptoms.
- Tip: Use a surge protector for your entire HVAC system, or consider installing a dedicated surge protection device for the thermostat.
Car Thermostat Replacement Costs
The thermostat car replacement cost can vary immensely. Some cars have complex engines, making it more difficult and time-consuming to access and replace the thermostat. Luxury or performance vehicles may have higher parts and labor costs.
The cost of a new thermostat can range from under $10 to $175 or even higher, depending on the brand and vehicle.
Consider the cost of coolant too. As well, labor costs for professional installation typically add $100 to $300, depending on the complexity of the job.
Repair costs can vary by region, with urban areas typically charging higher labor rates than rural or suburban locations. And don’t forget to factor in that labor rates are higher in areas where cost of living is higher.
Plus, if your thermostat failure is accompanied by other cooling system issues such as a faulty radiator or water pump, the overall repair cost will increase drastically.
Generally, you can expect to spend between $50 and $200 for a DIY thermostat replacement.
FAQs.
Q: How do you know if a car thermostat is working?
The easiest way to know if your car’s thermostat is working is by turning on your engine and allowing it to idle. Look into the radiator filler and observe if the coolant is flowing.
Since you’re just starting up the engine, the coolant should not be flowing now because it has not reached its operating temperature to open up.
If the engine runs for a while, the coolant is not flowing; it means the thermostat is stuck close. When you hear that the thermostat is stuck open or close, it means the thermostat is bad.
Q: What Happens When a thermostat fails?
A bad thermostat will not allow adequate coolant flow when required, resulting in engine overheating or lowering your engine temperature if it stays at a stuck open position, affecting your engine lubricating force.
When the engine is not functioning correctly due to low engine oil temperature caused by a stuck-open thermostat, the engine will experience rough idle; hence, the phrase, bad thermostat rough idle.
Q: Can a bad thermostat cause engine to Overheat?
A stuck-close thermostat will not allow coolant passage to the radiator for the cooling process, thereby causing the engine to heat up swiftly and eventually cause an engine to Overheat.
Q: Why would the thermostat stop work?
What causes a water pump to fail? Several factors could cause the thermostat to stop functioning correctly, such as a blown a fuse in your fuse box, or tripped breaker, or a dead battery. If these components are working in order, it could be a faulty inner component.
Q: How do I know if my thermostat or water pump is bad?
A bad water pump and thermostat will give similar symptoms when any of them go bad since both components help recirculate and allow coolant passage in the engine, respectively.
When you see any of the following signs, it is an indication that you have a water pump or thermostat.
- Engine Overheating
- Temperature gauge fluctuations
- Coolant leaks from the front of your car
- Steam coming from the front of your car
- Nosey or loosened water pump pulley
- Coolant leaks around the thermostat housing
Final Thought
At this point, you must have known the symptoms of a stuck open thermostat, symptoms of a bad thermostat, and how to fix bad thermostat problems.
You might notice just one or two of the outlined symptoms when your thermostat goes bad.
So, once you notice any of these symptoms, you want to diagnose and replace a bad thermostat, or better still, contact a professional mechanic for proper inspection and repair.