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Thermostat Housing: What Is It and Should I Replace It?

Thermostat Housing

A car has a cooling system that makes sure the engine maintains its optimal operating temperatures while it is being driven. The thermostat is part of the cooling system. It is responsible for regulating the flow of coolant between the engine and radiator. It stays open to let the coolant flow into the engine that helps maintain its normal operating temperature. The thermostat housing on the other hand functions as the coolant outlet and it is found on either the intake manifold or cylinder block. It is the one that holds the thermostat as it does its job.

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A car is usually equipped with either a stand-alone or an integrated thermostat housing. It is usually made of a high quality plastic composite, pot metal, aluminum, or other similar substance. Although the thermostat housing is typically made of high quality plastic or metal, it is still susceptible to damage since it is always exposed to extreme temperatures. It can become warped or cracked which can lead to a coolant leak. When this happens, you might ask, should I replace it? Yes, you should! Ignoring a coolant leak can lead to very serious engine damage. A thermostat housing replacement will usually cost you around $50 to $250 on parts and around $130 to $170 for the labor costs.



Thermostat Housing: What is a Thermostat Housing?



A car that is equipped with an internal combustion engine has a thermostat housing that functions as a coolant outlet. It is usually located on the cylinder head or the engine block. To ensure that the engine is always running at its optimal operating temperature, engine coolant is constantly flowing and it flows through the ports in the head and block. The coolant flows through these components, through the thermostat housing, and into the radiator where it will be cooled.


Thermostats in cars function by delaying the circulation of the coolant just until the engine is warmed up. The thermostat housing on the engine side is a wax-filled cylinder. It enables the engine coolant to flow through when the radiator has boiled up beyond the designated operating temperature. For the valve to open, the wax will be melted and the hose will expand so the coolant can flow. This can be achieved since there is a small rod connected to a closed valve when the engine is cold. When the wax is melted, it will expand and this pushes the rod which opens the valve, allowing the free flow of coolant.


The thermostat housing can also function as an air bleed point for the cooling system. It might be equipped with a bleed valve that can be loosed to let any air trapped in the block escape. Although not all cars have this feature, this will work great and be very useful whenever the cooling system is drained, refilled, or flushed out.


Even if you have a standalone thermostat or one that is integrated into the thermostat housing, how it functions stays the same. However, when your thermostat housing is faulty, the repair procedure can vary depending on the type of thermostat embedded in your car. For standalone systems, you will have to guess around which housing is damaged and is leaking. This causes a reduced cooling performance.


If your car is equipped with an integrated system, you can change the whole thermostat quickly and this reduces the chances of missing a thermostat housing leak. This can also help reduce the risk of possibly damaging other hoses when replacing a thermostat housing. The integrated system means that the thermostat and the housing are one. It is much easier to replace the whole unit, needing no special tools and if the thermostat has been fixed permanently into the housing, you don’t have to worry about it being installed incorrectly.



Thermostat Housing: What are the Symptoms of a Bad Thermostat Housing?



The thermostat housing plays an important role in the car’s cooling system. It is the one in charge of regulating the coolant intake inside the engine bay. Engine coolant is important since it transfers the engine heat out to the radiator bay and is dispersed into the air. If there is an incorrect amount of engine coolant in the engine bay, it can cause engine problems or even engine overheating. That is why if you notice any signs or symptoms of a bad thermostat housing, you should address the problem immediately and have it fixed.


But what are the symptoms of a bad thermostat housing? The common symptoms of bad thermostat housing include:


  • Temperature gauge high readings


Since the temperature housing functions by opening and closing at the precise times to regulate the coolant flow, if there is a problem somewhere or an electrical issue, the housing won’t be able to detect the engine’s temperature. When this happens, it might not open, causing the coolant to not flow, which can lead to an extremely hot engine temperature.


  • Erratic temperature readings


Erratic temperature readings can be one of the symptoms of a bad thermostat housing. The thermostat within the housing has an idea what the engine’s temperature is. If the system constantly misreads the temperature, it can cause problems since it won’t know when to open and close, and it needs to open and close at a very precise timing. When this happens, it can lead to an erratic amount of coolant being released into the engine or backed up, which can result in changing temperatures. You might notice these erratic temperature readings on your car’s dashboard. The moment you notice this problem, it is best to have your car checked as soon as possible.


  • Coolant leaking


If you notice that there is coolant leaking on the surface underneath your car, it is an indication that there is a problem somewhere. You need to have it checked. The faulty thermostat housing refusing to open can create a pressure that can lead to a number of leaks in the coolant hose areas.


Although the thermostat housing is usually made with high quality plastic or metal, whether it may be a standalone or an integrated thermostat housing, it can still become damaged because of constant exposure to extreme temperatures. The movement in the rubber hose can also cause your car’s thermostat to develop a leak. When the thermostat housing becomes warped, cracked, or damaged in any way, it can also cause a coolant leak. When this happens, you should have it corrected immediately since it can cause your engine to overheat. .


How will you know if your thermostat housing is leaking? You will know if your thermostat housing is leaking when you experience any of these issues.


  • High temperature reading.


If your faulty thermostat is stuck closed, you may find a high temperature reading on your temperature gauge. If you notice this problem, you need to have it repaired immediately since it can potentially damage your engine components if you ignore this problem and continue driving your car.


  • Thermostat valve stuck open.


If the problem is a thermostat valve that is stuck open or when the valve opens too soon, it can cause a leak in the thermostat housing. The leaking can become so severe that the engine coolant can become so low. When this happens, it can cause some severe damage on your engine when the problem is not addressed immediately.


  • OBD II trouble codes present.


Since the thermostat is faulty, it can happen that the engine won’t be fully warmed up and will be running cold. An engine that is healthy usually runs just above 200 degrees that is right near the center of the temperature gauge. If your engine is running cold, it will set off the trouble codes P0128 or P0125. When you see this trouble code, you need to have it fixed immediately since it can cause the engine to develop sludge over time which can damage the engine.


  • Illuminating low coolant warning light.


If your coolant level drops below the normal range, the low coolant warning light on your car’s dashboard will be turned on. When you notice that you have an illuminating low coolant warning light, it can be an indication that you have a leaking thermostat housing. You might also notice that your check engine light is illuminating since it can also cause your engine to overheat.


  • Car heater does not work.


The heater of your car relies on the hot engine coolant to function properly. If your thermostat housing is leaking, it can lead to a low coolant level, which can cause your heater to not function.



Thermostat Housing: Should You Replace Thermostat Housing?



When your thermostat housing is damaged and is starting to leak, a replacement might be needed to fix the problem. A replacement will also be required if there is a pitting developing on the gasket surface that can be spotted once the housing is removed for a thermostat service. Coolant that has broken down can become acidic and can also attack metal such as the water pump’s internal components or the thermostat housing’s mounting surface. If this problem occurs, a thermostat housing replacement is necessary.


If you are asking if you can still drive a car with a leaking thermostat housing or if you should really replace a faulty thermostat housing, then here’s what you need to know. While it is possible that you can still drive your car even if it has a leaking thermostat housing, the experts are not recommending it. You should not attempt to drive it since your engine will be more prone to damage since it does not have the right mechanisms to protect your engine. If you ignore the problem, it can lead to irreversible damage to your engine and it is something you don’t want to deal with. It is best to take your car to an auto repair shop and have it serviced as soon as possible.


What happens if you don’t replace your faulty thermostat housing? If you ignore the problem, you will most likely experience these issues.


  • Your engine will overheat.


If the faulty thermostat remains closed, the engine bay won’t be able to receive the cooling it requires. When this happens, it can cause your engine to overheat and this can be very harmful to your engine. If your engine continues to overheat, it can result in its components to become damaged or even total engine failure that can render your car undrivable. Depending on your car’s condition or its market value, it might not be worth it repairing if this problem happens. Selling your damaged car might be your only option.


  • Improper coolant flow.


If you suspect that you have this problem, you can check if you have a faulty thermostat housing yourself. To check it, you will just have to pop your hood open, lift it up, and find the radiator cap. Make sure that your engine has cooled down before you touch anything under the hood. Open the radiator cap, and start your engine. Then look closely at the opening. You should see no movement, with the coolant not flowing through an opening thermostat housing. If you see some movement, then it means that there is a problem and you need to have it checked.


  • Coolant hoses are cold.


Another thing that you can check when you have a faulty thermostat housing is when you turn on the engine, after not driving it for a few hours, and feel the coolant hose’s temperature. Make sure that you won’t touch the engine when feeling the hoses. Then feel the hose again after 10 minutes. The hose should be a bit hotter this time but if it is not, it means that the thermostat housing is not opening as it’s supposed to.


If your car needs a thermostat housing replacement, you need to have it done as soon as possible. The replacement will usually cost you around $50 to $250 on parts while the labor costs can be somewhere around $130 to $170. You should also expect that the total cost can be a bit higher when you have to repair some other related components as well. The thermostat housing is an important part of your car that is why you need to make sure that it is always in good working condition.



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