How to tell if your Coolant Temp Sensor is Bad

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There are a vast number of sensors in a vehicle that can cause your check engine light to come on, but none more common than the coolant temp sensor. It has an extremely important job – telling the PCM (engine computer) how hot your engine is.

It is part of the vehicle’s cooling system, which delivers coolant (A/C refrigerant) throughout the engine compartment to absorb heat from the engine. The PCM uses information from the coolant temp sensor along with inputs from other sensors in your car to determine how much fuel is needed for optimal performance and efficiency.

If it is faulty, you may notice that the car doesn’t run quite right or you could even be stranded on the side of the road.

The Coolant Temp Sensor (CTS) may be one of the most important sensors in your car, so it is worth checking up on every once and a while. A bad CTS may cause many problems that will affect other parts of your engine. Symptoms include: overheating, lack of power, decreased gas mileage and timing issues just to name a few.

What Does the Coolant Temperature Sensor Do?

Well simply put, it’s a sensor that tells your car if the engine is running hot or not. If for some reason this sensor does not work or is faulty, then your cooling system will start malfunctioning and may cause serious damage. This sensor works by sending out an electrical signal which varies depending on how hot the engine is. So, if you check up on this sensor every once and a while it will allow you to get ahead of any potential problems before they get out of hand.

The CTS is responsible for telling the ECU (Engine Control Unit) what temperature the coolant is. This is important because when the temperature is too hot, it will send a signal to the ECU that shuts down your car’s fuel injection system. This is to prevent any further damage from overheating. So, if this sensor stops working your vehicle could be at risk of overheating which can cause serious problems for other parts of the engine.

Symptoms of a Bad Coolant Temp Sensor

The following are just a few ways that you can check on your own to see if your coolant temp sensor is bad.

Symptoms of a bad CTS are wide-ranging, but here are some things you may experience:

Check Engine Light

The dashboard check engine light is a warning sign that your CTS may be bad. The check engine light will come on and stay on until you take your vehicle to a professional mechanic. The check engine light means that the coolant temp sensor has sent out an error code that can either mean something is wrong or it isn’t working correctly.

Poor Mileage

The fuel efficiency of your engine depends on the level of heat it is producing. If you have a faulty coolant temp sensor then that means that your car’s temperature is no longer being measured correctly, which results in lower mileage due to less efficiency.

Electrical Cooling Fans not coming on

The fans present in the engine responsible for cooling the engine may not turn on if the coolant temp sensor is bad because it can’t effectively measure how much heat is in the engine.

Black Smoke from the Exhaust Pipe

If you see smoke coming from your exhaust pipe then this is a sign that your engine is producing too much heat and the coolant temp sensor has failed to detect it.

Difficult Starting Condition

When turning the ignition key the engine may be difficult to start or it may not even turn on at all. This is because the coolant temp sensor has an influence over the ignition system of your car in terms of the air/fuel mixture.

Engine Overheating

If the coolant temp sensor doesn’t work correctly, then your car will run hotter than it should due to the sensor not being able to detect the heat level properly which ends up over heating your engine. When this happens, your car’s radiator fan may activate but your cooling system can still become overheated if it begins to malfunction.

Poor Idling

If your engine is overheating while idling more than likely the coolant temp sensor has stopped working or failed. An idling car should not be getting hot, but if it is then there is an underlying issue here that needs to be fixed before you end

Poor Engine performance

If there are problems with the cooling system then this will lead to an increase in heat which will cause loss of power, hesitation, and stalling. This can be a very dangerous situation if not handled as it may lead to engine failure.

Coolant Temperature Sensor Location

The sensor itself can be found in the high-temperature coolant hose which is located between the thermostat housing unit and the engine or it can also be located in one of two places. The first place would be near the cylinder head close to where the intake manifold meets up with it, while another place for this sensor is under your car’s hood on top of your engine block.

The temperature sensor needs to be checked every once and a while no matter what type you have because they are all prone to breaking down at some point or another. Checking up on your CTS regularly will save you time and money when compared to waiting for something big like an overheat to happen.

Coolant Temperature Sensor Replacement Cost

The cost for replacement may range depending on the amount of labor, but in general, it should cost around $100-$150 to fix. Labor costs will add onto this and can cause the total bill to be anywhere from $30, for just a basic replacement job, upwards to $200 when extensive labor is performed.

Parts such as coolant sensors are not covered under warranty unless they fail within the manufacturer’s mileage limit so you might have to pay upfront in order to get your car fixed. When purchasing a new sensor consider buying one made by an OEM supplier because they tend to last longer than generics.

How To Make the Coolant Temperature Sensor Last Longer?

Generally speaking, oil and water do not mix, but that is exactly what the sensor has to work with due to its location. To prevent this from causing problems then you should clean any residue or simply make sure that you keep the reservoir topped off with coolant. To make the sensor work correctly you should drive within the engine’s optimal temperature range for best results.

Oil Contamination

If there is a major issue with oil in your car’s cooling system then this will result in overheating and can damage other components besides just the CTS which results in more repair costs overall. If there seems to be an issue with this then get everything checked out immediately because it can lead to serious long-term damage to your car.

Coolant Contamination

Another issue that you will have to avoid if possible is coolant contamination because it can cause the sensor to fail as well as potential damage to other components around it. If there is a coolant problem then you should consider changing out all of the coolant in order to save yourself some hassle at a later date. It’s better to be safe than sorry so this kind of precautionary measure may just save you from having a few hundred dollars’ worth of repair costs later on down the road.

Overuse Of Cooling System Additives and Treatment Products

If you use products such as antifreeze, radiator stop leak, and corrosion inhibitors, then be sure that they are meant for your car’s cooling system. Using the wrong type of product can cause problems with the CTS and potential damage to other components which will end up costing you more money in the long run.

Not Maintaining Your Cooling System

Maintaining your coolant regularly by cleaning out any rust or debris that may be sitting in it is necessary if you want your CTS to last. If there are not enough additives, then the water itself can become corrosive over time and eat away at vital engine parts like gaskets, valves, water pumps, etc. This will lead to an expensive repair bill which would have been easily preventable had you kept up on maintenance regularly.

Conclusion 

In conclusion, the Coolant Temperature Sensor functions to monitor engine temperature by sending data back to your car’s computer. You can tell if it has gone bad simply by noticing symptoms like a check engine light and the temperature gauge in the dash reads in an abnormal range. If this happens then consider having it replaced as soon as possible to avoid any further problems with your car’s cooling system.

There are many problems that can arise with this part including oil contamination, coolant contamination, overuse of additive products, and not maintaining the cooling system regularly. It is best to keep up on maintenance in order to avoid these kinds of issues because they could lead to you having a very expensive repair bill later down the road.

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