How to Replace a Faulty Thermostat

Sep 26, 2019

How to Replace a Faulty Thermostat

Are you finding that your car’s engine warms up very slowly? Is it not reaching the normal temperature? Or maybe you are experiencing overheating? You could have a faulty thermostat on your hands!

But how can you tell if it is the thermostat that is acting up and not something like a failing water pump, radiator or fan causing the above problems. When a thermostat gives out, it will be stuck in either an opened or closed position.

What does a car thermostat do?

Basically, a thermostat will start in the closed position, as the engine starts it will help to reach operating temperature. When the coolant levels begin rising, the thermostat will open. This allows the hot coolant in the engine to flow into the radiator, then the water pump will push lower-temperature coolant from the radiator to the engine. As the lower-temperature coolant reaches the car's thermostat, the expanding fluid will contract, closing the thermostat's valve.

Removing and replacing a car thermostat

  • If your car has a normal top-mounted thermostat, you need to drain only part of the engine’s cooling system. Do not do this while the engine is hot! Make sure the engine is cool before doing this.
  • Drain the coolant from the radiator tap, or from the bottom hose, until it is below the level of the thermostat housing.
  • Drain into a clean container to allow you to reuse it. Filter it before pouring it back.
  • Disconnect top hose from thermostat housing by loosening host clip. Carefully ease hose off.
  • Remove nuts securing the housing. If this does not lift, tap with a piece of wood.
  • Lift out the thermostat, if the engine is cold but the thermostat is opened, it must be renewed.
  • Before inserting new thermostat, remove all traces of old housing gasket carefully.
  • Insert the new thermostat then smear the new housing gasket lightly with a non-setting sealing compound.
  • Fit it and the housing in place. Tighten housing nuts. Be careful not to over tighten!
  • Top up or refill with coolant.

If you don’t want to replace the thermostat yourself, enter your reg number today to get quotes from local mechanics in your area who can replace it for you!


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