Once we were asked by a curious driver a really weird question. He said: "Guys, you know a lot about cars. Tell me please what it means when your car is always on "C"!
Engine overheating highlights
- Level of urgency:very high
- Commonreasons:low coolant, thermostat problems, coolant blockage, radiator fan problem
- DIY diagnostics:possible but complicated
- DIY repair:impossible
- Price of repair:$300 - $650
- Time for repair:3 - 6 hours
- If ignored:engine failure, low performance, cooling equipment damage
The engine temperature gauge and its important
When someone says that their car is on C, they probably mean that the engine temperature gauge always shows low engine temperature. See stands for "Cold" or "Cool" and means that the engine coolant is cold. While H stands on the other side of the same gauge and means "Hot" and shows that the coolant is too hot to keep driving.
In normal conditions, when you start your vehicle, the coolant temperature gauge should be on C showing that the engine is cold. After a minute or two, depending on the air temperature outside, the gauge should slowly go up and finally stop somewhere near the middle. This is the standard behavior of the temperature gauge which tells you that the engine cooling system is working properly and efficiently.
If you see that the gauge is lying calmly on C always or starts raising too slowly and only after a lot of time, this indicates that the cooling system has some problems.
What can make the coolant temperature gauge lie on C?
There are clearly several reasons why the cooling system may go wrong and the coolant may be cold all the time. It doesn't depend much on the air temperature outside. It may only slightly change the time of heating up your vehicle.
Here are some of the most common issues that can cause these problems:
1. Thermostat failure
A failed thermostat may have been stuck open. It means that the coolant will always circulate through the radiator. When the vehicle is cold, the thermostat should close the big circle and the coolant should be circulating only within the engine to reach the working temperature quickly. If the thermostat is stuck open, the coolant may heat up for too long and you'll see the gauge lying on C.
There is only one remedy in this situation - you may buy the new thermostat and have it replaced. After that, the engine coolant should start heating up as it's meant to do.
2. The gauge is dead
It's a not really common issue but it's still worth checking up on. Sometimes, the dash doesn't work properly and you may see the engine temperature gauge lying on C. Also, if this is the case, your main radiator in the vehicle will be warm or hot after you drive for 10-15 minutes. Just open the hood after driving for some time and carefully touch the radiator. Be careful - you may burn yourself!
Also, the problem may be not in the dash or gauge itself but in the wiring. If some wire lost connection, you may not see the dash gauge working properly although the engine temperature goes up as it should.
3. Engine temperature sensor is broken
The gauge gets all the information about the temperature of the engine coolant from the sensor that measures the temperatures and sends signals to the ECU and to the dash. If this sensor malfunctions, you will not see the gauge moving because it just doesn't get any signal and can't rely on any information about the coolant temperature.
In some cars, different sensors work for the gauge and for the ECU. If not, there will also be a check engine light on the dash because the ECU sees that something is wrong with the vehicle.
4. Some other problems with the cooling system
If the temperature gauge always stays on C, you should have the cooling system checked and diagnosed thoroughly. The system may have no coolant in it or some sensors or wiring may be damaged. Whatever happened with the system, you should make sure the problem is fixed before you drive your vehicle for more than 5-10 minutes. Otherwise, you may overheat the engine and end up repairing your vehicle for a lot of money.
So, we hope we've answered all your questions about the gauge showing engine temperature and staying on the C all the time.
About the authors
The CarAraC research team is composed of seasoned auto mechanics and automotive industry professionals, including individuals with advanced degrees and certifications in their field. Our team members boast prestigious credentials, reflecting their extensive knowledge and skills. These qualifications include: IMI: Institute of the Motor Industry, ASE-Certified Master Automobile Technicians; Coventry University, Graduate of MA in Automotive Journalism; Politecnico di Torino, Italy, MS Automotive Engineering; Ss. Cyril and Methodius University in Skopje, Mechanical University in Skopje; TOC Automotive College; DHA Suffa University, Department of Mechanical Engineering
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