Car Engine Overheat Issue and Its Possible Causes

Engine Over-temperature Problem

Car Engine Overheat Issue

In summer season particularly, car engine overheat issue surfaces as the biggest concern on most vehicles. Engine overheat issue could be a consequence of multiple reasons. A misconception prevails in the minds of many that engine overheat issue in Suzuki Liana is a design problem, whereas it certainly is not. In order to clarify the ambiguities, i decided to write this blog to cover Engine Overheat Issue and Its Possible Causes. It is pertinent to mention that this blog is not limited to Suzuki Liana/Aerio operators only, rather is equally applicable to all other makes of cars as well.

Ok let’s start the discussion:-


Firstly, lets recap what indications that appear when engine heats up. ECT sensor (Engine Coolant Temperature sensor) senses the engine coolant temperature and indicates on Temperature gauge or Over-Temp indication light. However, there have been many reported instances where the engine got heated up without showing over-temp condition on gauge / light. This happens when the coolant depletes rapidly (generally due to heavy leakage), because of which the coolant does not come in contact with ECT Sensor, resulting in failure to show the actual engine temperature indication. Other than the primary temperature indication, one should also be cautious about any one of the following symptoms which could also be a consequence of engine heat up issue:-

  1. Air Cond air temperature rises to normal air. In actual, the AC compressor automatically trips if engine temperature rises above limits. AC Compressor does not restart unless the overheat condition is removed.
  2. Engine may produce ‘knocking’ sound during acceleration.
  3. Burning Smell from the car or from the open windows.
  4. Smoke from under the hood.

Possible Causes of Engine Overheat Issue

Car engine overheat issue can be caused by either of the following SIX broad categories:-

  1. Coolant Related problems
  2. Electrical Malfunctions
  3. Components Malfunctions
  4. Core Engine issues
  5. Peculiar Situations

Lets discuss each of these categories in detail so that readers move in right direction for troubleshooting of engine overheat issues….

1. Coolant Related Problem


  • Insufficient or no coolant (water) in radiator. Checking sufficient Coolant (water) level on daily basis prior to first drive of the day is a preferable practice.
  • Coolant leakage due to ruptured water hoses can deplete the coolant rapidly, resulting in instantaneous rise of engine temperature during the drive. As a good driving practice, Gauges/indications must be scanned at-least once every 2-minutes interval (i.e 120 seconds).
  • Blockage or restriction in coolant circulation system may result in engine overheat issue due to ineffective cooling by radiator.
  • Radiator may get contaminated with dirt/sand deposits over a period of time, because of these contaminants (dirt/sand) the cooling efficiency of radiator drops which ultimately cause engine overheat issue. Radiator may be cleaned from external side preferably with every car-wash, and internally flushed every 10,000 KMs of drive.

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2. Electrical Malfunctions

a. Radiator Fan Problem

Radiator fan blows air over the radiator-fins to cool down the coolant passing from the radiator. ECT sensor (Engine Coolant Temperature Sensor) automatically controls the radiator fan by giveing an electrical signal to the fan for its operation. The fan automatically starts operating when the engine coolant temperature rises, and shuts down when the coolant temperature drops within limits.

If the fan fails to operate when the engine heats-up, then either the fan has some electrical problem or the ECT sensor has gone faulty, which is not sending signal to fan for operation. This situation can be troubleshooted by removing the ECT sensor connector. If the fan starts operating then the ECT sensor is faulty, otherwise there is an issue with the fan. If the fan starts operating, it is advisable to keeps the fan running (with removed ECT sensor connector) for reaching up to the nearest maintenance center.

b. Slow Fan Speed

Another possibility of engine overheat issue could be the slow rotational speed of the radiator fan. This may happen either the proper voltage is not available to the fan, or the fan itself has become slow due to weak internal electrical coil. Fan speed may be check by making a direct connection with battery, if the fan speed increases it shows that sufficient voltage is not available to the fan, may be due to voltage drop owing to bad wiring or the bad earth connection.

c. Fan Rotational Direction

Another situation has been reported where after some maintenance on electrical system, the car starts to heat up. On investigations it was revealed that the direction of fan rotation became reverse, resulting in air blow in opposite direction (i.e throwing air from rear to front). In normal operation, fan rotates to blow air from front to rear, so that during driving the air coming from the front augments the air flow over radiator fins. However if rotational direction is reversed, the incoming air will counter the air flow produced by the fan, resulting in an ineffective heat exchange in radiator which will ultimately cause an engine overheat issue.

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3. Components Malfunctions

a. Radiator Cap

Radiator Cap plays a very important role in maintaining pressure in the engine cooling system. The cap acts as a pressure relief valve in the event of steam generation in the cooling system due to insufficient coolant quantity. Radiator cap has a spring-loaded lid that prevents the coolant from leaking from the filler neck. However, over the years of use, the cap spring gets hardened due to persistent exposure to high temperature vapors. This condition makes the cap ineffective because of which the pressure gets trapped in the cooling system and results in engine overheat issue. Replacing radiator cap with a good quality cap often addresses the engine overheat issue with least expenditure

b. Thermostat Valve

Thermostat Valve is an important component of coolant system. It restricts the coolant circulation through radiator when engine is cold (usually in winters or for the first start of the day). The thermostat valve remains closed until the engine reaches its operating temperature (temp gauge needle at ‘Half’ position) when the engine is cold and proportionally opens as the engine warms up. If the thermostat valve looses its effectiveness, it sometimes becomes less sensitive to coolant temperature because of which it either opens partially or may not open at all i.e stuck at closed position, does not allow the coolant to circulate through the radiator, resulting in engine overheat issue.

c. Engine Coolant Temperature (ECT) Sensor

Engine Coolant Temperature (ECT) Sensor senses engine coolant temperature and generates two signals; one for the temperature gauge/indication light, while the other signal for radiator fan operation. There could be a possibility of ECT sensor malfunction where it becomes less sensitive to temperature resulting in showing less temperature on gauge whereas in actually engine overheat issue prevailed. Meanwhile it also does not send signal to radiator fan which further aggravates the engine over-temp condition.

d. Water Pump

Water Pump (usually known as water body locally) forces the coolant to circulation within the cooling system, when it fails, it stops pumping action causing water stagnation in the cooling system, which will rise the coolant temperature as the cooling action of coolant does not take place in the radiator. Hence failure of Water pump will also result in engine overheat issue.

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4. Core Engine Issues

a. Insufficient Engine Oil Quantity

Less engine oil quantity causes improper lubrication of moving parts, hence producing more friction and resulting in engine overheat issue. If this situation prevails for extended period, it may result in engine seizure.

b. Tappet Adjustment

Improper tappet adjustment (over-torqued) will make the engine hard to operate hence requiring more power by the engine. Hence, restricted engine operation may also result in engine overheat issue.

c. Belt Size / Tension

Improper Belt sizes and tension may cause hard engine operation resulting in engine overheat issue due to engine overloaded.

d. Bearings / Pulleys

Dried out bearings and pulleys induce excessive friction in moving parts which overloads the engine, which may also contribute to engine temperature rise.

e. Head Gasket

Head Gasket damage or burn-out is one of the main contributor towards car engine overheat issues. Engine Head gasket is installed between ‘engine block’ and the ‘engine head’, it prevents coolant and Oil intermixing and also caters for minor imperfections between mating surfaces of ‘Block’ and ‘Head’.

f. Excessive Friction

Misaligned Engine Pistons or worn out engine rings may also cause excessive friction in the cylinders which may also result in engine overheat issue.

g. Engine Head/Block Issue

Cracked Engine Head or Block may let the coolant to enter into cylinder resulting in loss of coolant which may ultimately cause engine overheat issue. Conversely, the cylinder pressure may also be leaked into coolant /oil channels of Block or Head resulting in coolant system pressurization will ultimately result in engine overheat issue.

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5. Peculiar Situations

a. Engine Heat up issue with Air Conditioning ‘ON’

Following could be the possible causes:-

  • Condenser fan not operating with AC switch put to ‘ON’, possible electrical issue.
  • Hard AC compressor bearing or stretched belt may generate additional load on car engine with AC ‘ON’.
  • Weak engine that fails to take additional load of AC compressor.

b. Engine Overheat issue during drive only

Following could be the possible reasons if engine heats up during drive only:-

  • Catchy brakes
  • Dried out wheel bearings
  • Less gear oil quantity
  • Reverse rotational direction of radiator or condenser fan.

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6 comments on “Car Engine Overheat Issue and Its Possible Causes”

  1. Wajahat Baig

    O have liana 2006 sports. I m facing some problem related engine heat up. On a.c engine is normal, but without a.c engine boils water nd on open radiator cap it throws water out nd also stsams out water. On sunday I travel to gujr khan from jhelum engine was heated up nd gas kit was failed, I installed new one nd make radiator clean, mechanic chek it with a.c but when I drive car without a.c it again boiled water….
    Can u please guide me, nd help me out to reaolve this issue…
    Ect is working properly

    • Suzuki Liana Pk

      Please note when AC is ON, two fans are running to cool the engine, in normal condition only one radiator fan works. Please check following:
      1. Is the fan speed good? sometimes the fan brushes get weak resulting in slow fan speed.
      2. Most common issue with Liana is that its Thermostat valve becomes faulty which restricts the coolant circulation, get it checked or replaced. (located underside of the intake manifold, takes 4-5 hrs for its replacement, so go to some proficient mechanic)
      3. Get the Radiator cap replaced with genuine one.
      Hope this will resolve overheating issue.

  2. Moosa Hassan

    My car (Alto) started to over heat if driven in temp above 40 degrees, while going constant over the speed of 80Km/h on Motorway (happened many time in that particular trip), although there was no leakage; coolant goes back in the side bottle and also steam is produces in side bottle. A mechanic told me it was issue of head gasket and he turned on fan directly.
    When I came back to lahore another mechanic told me it is because the radiator is clogged, and it solved my problem after getting it cleaned.


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