engine overheating causes

Engine Overheating Causes & Solutions

In Coolant by Josh SLeave a Comment

engine overheating causesAs you may know already, overheating are really bad for your engine and can cause serious damage to it and result in very high repair costs. But what are the most common engine overheating causes to know before you are starting your troubleshooting? Knowing the most common causes can speed up your troubleshooting and make you find the problem a lot faster and it will help you to not replace the wrong parts.

In this article, you will learn the most common causes of engine overheating and you will learn how to repair it as fast and cheap as possible.


Engine Overheating Causes & Solutions

ProblemCommon CausesSolutions
Engine OverheatingBad thermostat

Bad Waterpump

Bad Engine Coolant temperature sensor

Air in the coolant system

Faulty Radiator Fan

Clogged Radiator

Head Gasket

Clogged coolant hoses
Replace thermostat

Replace waterpump

Replace Engine coolant temperature sensor(S)

Bleed your coolant system

Replace Radiator Fan

Repair Radiator Fan wirings/relays/fuses

Replace Radiator

Replace Head gasket

Replace/Flush the coolant system


Engine Overheating Causes

There are many possible causes of engine overheating. I work as a diagnostic technician and on this list, I have noted the most common problems with engine overheating. Some of the problems are easy to fix and some require major repairs to your engine. When you are troubleshooting your car you can start to check the parts from the top of the list and go down. If you want a full list of how to troubleshoot your coolant system, check our article Overheating Troubleshooting.

The most common causes of engine overheating is a faulty thermostat, faulty CTS sensor, air locks in the coolant system, faulty radiator fan, faulty water pump or a faulty head gasket. You should always diagnose your car properly and do not just replace parts. Take help from a professional mechanic if you are not sure of how to diagnose it properly.

Faulty Thermostat

The thermostat is a really common problem when it comes to engine overheating. The thermostat is closing the coolant in the engine until it reaches 90 degrees to speed up the warm-up phase and to make sure the temperature is at the same temperature all the time. The engine is most efficient when the coolant is hot, and that’s why the engine is operating best when the coolant is hot. When the thermostat is faulty, it will not open the valve to let the coolant flow out when the temperature has reached 90 degrees which will result in that the temperature will keep rise until the engine is overheating.

Faulty Engine Coolant temperature sensor

A faulty engine coolant temperature sensor will result in that the cooling fans will not start when they are supposed to do. If you have an electric thermostat, the engine coolant temperature sensor could create problems with the thermostat also. To diagnose an ECT sensor, you could either to it with an OBD2 scanner or check it with a multimeter. To check it with a multimeter you have to find what ohms it should have related to the temperature and measure between the two pins. You can often have more than one engine coolant temperature sensor.

Air in the coolant system

Air in the coolant system is a common problem when it comes to engine overheating. Air bubbles in the coolant system will make the coolant to not flow as it should through the coolant system. Air in the coolant system could be from a repair, a coolant leak or a faulty head gasket. You should always bleed your cars coolant system after a repair. If you want to learn how to bleed your cars cooling system the best way, check out this article: Bleed your cars cooling system. Air could also be caused by a low coolant level, top up the coolant and bleed the system after to see if the problem is getting fixed.

Faulty Radiator Fan

A faulty radiator fan could result in that the coolant in the radiator won’t get cooled down if you stand still with your engine. A faulty radiator fan could be caused by faulty wiring to the fan, bad relay, blown fuse or a faulty engine coolant temperature sensor. In many cases, the radiator fan itself could also be faulty and have to be replaced. The radiator fan should start when the thermostat is opening and the CTS sensor for the fan reach 90 degrees.

Faulty Waterpump

A faulty water pump is also a common cause of engine overheating. The water pump is pumping around the coolant in the coolant system and pumping the coolant to the radiator to cool it down. If the water pump is faulty, the coolant will stay in the engine and will not get’s cooled down, which will result in an overheating engine. It could be hard to diagnose a faulty water pump without a flow meter or a temperature heat gun, so I can recommend checking the other things first. The water pump is in many cases driven by the timing belt and it requires a major repair to inspect and replace it. If there are noises coming from the water pump, replace it.

Faulty Head Gasket

Faulty head gaskets, when there is a leak between the cylinder chamber and the coolant system can often cause overheating. A faulty head gasket will push air into the coolant system and create air bubbles and cause it to overheat. You do often get coolant in the cylinder chamber also and there will often cause heavy white smoke from your exhaust pipe. Even small leaks on the head gasket can create air bubbles over time and it could be pretty hard to diagnose properly. Check our overheating article for more troubleshooting procedures of this fault.

Clogged Radiator or coolant hoses

Another cause, but not very common is a clogged radiator or coolant hoses from dirt. This can often be solved with a flush in the coolant system. Just remove the coolant hoses and flush the coolant system with water to see if you can get any dirt loose. In some cases, you have to replace the radiator. This is not a very common problem, but it’s an easy fix to try to flush the coolant system.



  • Always bleed your cooling system properly after any repairs to the system.
  • Always bleed your cooling system after you have filled up the coolant level if the level was really low.
  • A lot of parts in the coolant system can be hard to diagnose and if you are unsure, take help from an experienced mechanic.
  • A radiator/coolant flush is a cheap fix and can solve some coolant overheating problems.

If you have any other questions about engine overheating causes or want to tell us about how you fixed your overheating problems, comment down below. If you have any other car questions you are welcome to ask them at our homepage.

1 Star2 Stars3 Stars4 Stars5 Stars (15 votes, average: 5.00 out of 5)

Leave a Comment