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6 Most Common Problems of Cooling System [How to Detect Them]

Cooling System Problems

The most common cooling system problems fall into three common areas such as overcooling, high heat, and noise. The fourth problem is internal engine overheating. This is visualized as burned valves or scuffed pistons or rings, caused by overheating of the internal parts.

This guide will help you to take the first step in identifying these problems by explaining what could go wrong.

The troubles which usually occur in the cooling systems are as follows,

  1. Loss of liquids coolant due to leaks.
  2. Overheating.
  3. Overcooling.
  4. Incorrect temperature gauge reading.
  5. Noise.
  6. Frozen coolant.

1. Loss of liquids coolant due to leaks

The liquid coolant may leak from the cooling system. The External leaks can be noted by inspection, as the coolant comes out from the system.

The internal leak may allow some coolant to drain into the engine oil and is caused by a faulty head gasket, loose cylinder head, cracked or wrapped head, or cracked engine block.

If the leak is very great, it will raise the lubricating oil level in the oil pan. An internal leak may also produce clouds of white vapour in the exhaust gases.

2. Overheating

Cooling system problems - Overheating

Overheating is one of the main cooling system problems. It is caused by the insufficient quantity of water in the cooling system, coolant loss. Overheating without coolant loss. Overheating is caused by factors outside of the cooling system.

It is also caused by the clogged radiator and water passages, slipping from a belt, inoperative thermostat, late ignition timing, incorrect valve timing, pre-ignition, too tight bearings, too low engine oil level, clogged exhaust system, etc.

3. Overcooling

Cooling system problems - Overcooling

An engine is said to be overcooled if it is running below the normal operating range. This problem generally appears in the winter because the heater does not work. Overcooling is caused by a thermostat that opens too soon or remains open at all times.

It is also caused by the coolant by pass valve remaining open. The thermostat is usually located inside the upper coolant outlet of the engine. Remove the thermostat, test for its faults, and then replace it.

An overcooled engine can suffer from the following : 

  1. The engine does not achieve full power.
  2. Increased cylinder wear.
  3. Lower thermal efficiency i.e. more consumption of fuel.
  4. The oil does not thin out properly and increases the amount of fluid friction loss.

4. Incorrect Temperature Gauge Reading

Temperature Gauge in car

The temperature indicator or gauge fitted on the instrument panel may be faulty to give the incorrect reading. If it is faulty, it should be either replaced or corrected. A rapid check is no measure of the temperature of the cooling water in the radiator upper tank with a thermometer and compares it with the reading of the gauge.

5. Noise

Noises in the cooling system may occur due to the dry bearing, a loose pulley on the pump shaft, an impeller loose on the shaft, or two much end plat in the shaft. Some pumps require the addition of a special water-pump lubricant to the coolant by which the operation becomes noiseless.

6. Frozen Coolant

The water may freeze in the cooling system, especially when the car is parked where the temperature is below the freezing point. This fails the cooling system completely and may cause serious breakage of any part of the system. It is always advisable to check the cooling system for possible damage by the frozen coolant before operating the vehicle.

If the coolant is frozen, the engine can be tun at idling speed until it reaches a temperature of 200°C. During this operation, any loss of coolant due to the formation of steam must be continually replenished in order to keep the system as nearly as full as possible. The vehicle should not be driven until the entire coolant is in circulation in the system.

Summary of Cooling System Problems:

External Leakage

  1. Loose hose clips.
  2. Defective rubber hose.
  3. Damaged radiator seams.
  4. Excessive wear in the water pump.
  5. Loose core plugs.
  6. Damaged gaskets.
  7. Leaks in the heater connection or plugs.
  8. Leak at the water temperature gauge plugs.

Internal Leakage

  1. Defective cylinder head gasket.
  2. Cracked cylinder wall.
  3. Loose cylinder head bolt.

Water Loss

  1. Boiling.
  2. External or internal leakage.
  3. Restricted radiator or inoperative thermostat.

Poor Circulation

  1. Restricted in the system.
  2. Insufficient coolant.
  3. Inoperative water pump.
  4. Loose fan belt.
  5. Inoperative thermostat.


  1. Excessive impurity in the water.
  2. Infrequent flushing and draining of the system.
  3. Incorrect anti-freeze mixture.


  1. Poor circulation due to any reason.
  2. Dirty oil and sludge in the system.
  3. Radiator fins choked.
  4. Incorrect ignition system.
  5. Incorrect valve timing.
  6. Low oil level.
  7. Tight engine.
  8. Engine oil too thick.
  9. Clogged exhaust system.
  10. Dragging brakes.


  1. Defective thermostat.
  2. Inaccurate temperature gauge.

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About Saif M

Saif M. is a Mechanical Engineer by profession. He completed his engineering studies in 2014 and is currently working in a large firm as Mechanical Engineer. He is also an author and editor at www.theengineerspost.com

16 thoughts on “6 Most Common Problems of Cooling System [How to Detect Them]”

  1. Hi,
    I liked your group. It gives me very useful information. Plz send me pdf file on my email address. Thanks


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