It’s the thermostat that stops the engine from overheating, so it’s worth knowing how to replace the thermostat on your car.
It will save you time, money and, potentially, a blown gasket.
What does the thermostat do?
The thermostat is a valve that regulates the flow of coolant through the engine.
It prevents the engine from overheating and optimises the ambient conditions inside the car by distributing warm air via the heater.
If the thermostat malfunctions, the vehicle’s entire cooling system is inoperable.
When that happens, the engine overheats and the head can warp, causing a blown head gasket.
One way to avoid an expensive outing to the auto repair workshop is to replace the thermostat on your car yourself before it damages the engine.
Indications of a faulty thermostat
A thermostat usually malfunctions in one of two ways:
- the valve gets stuck in the open position, allowing the coolant to circulate constantly through the engine and radiator, or
- it gets jammed in the closed position, trapping the coolant in the engine.
When the heater inside the car doesn’t emit any heat – and the indicator temperature of the car stays low after travelling for a few kilometres – that’s a sign the thermostat is probably stuck in the open position.
Conversely, when the temperature indicator on the dash rises quickly and starts flashing, it’s a clear warning the engine is overheating.
Although there are several factors that can cause overheating, replacing the thermostat is a comparatively inexpensive job that will determine if further investigation is required.
Where to find the thermostat on your car
Most cars have a top-mounted thermostat located close to the water pump on the cylinder head.
The top radiator hose feeds coolant through the thermostat into the engine.
If you can’t locate the thermostat, simply follow the hose until you see the housing containing the thermostat where the hose joins the engine.
How to test your car’s thermostat
It’s a good idea to conduct a quick test before removing and replacing the thermostat.
Start the car when the engine is cold and place your hand on the top radiator hose. Take care to avoid the radiator fan.
When the thermostat is functioning properly, the hose will stay cool to the touch for a minute or two before quickly warming up.
If the hose starts warming up immediately, the valve is stuck open.
If it remains cool and the engine gets hot, the valve is permanently closed.
Tips for removing and replacing the thermostat
You will need:
- drip tray
- socket set
- flathead screwdriver
- non-adhesive sealant
- an old rag
- used nail brush
- fresh coolant to top up the radiator.
Place the drip tray under the engine to avoid getting coolant on the floor.
Use the screwdriver to loosen the clamp from the top radiator hose before easing the hose off the thermostat housing.
Unscrew the nuts attaching the housing to the engine with a socket wrench and lift the housing off the engine.
Remove the thermostat and gasket.
Tip: if the housing doesn’t come off easily, tap it gently with a piece of wood to loosen it.
Insert a rag into the gap left by the thermostat and use the brush to remove debris left by the housing gasket.
When the surface is completely smooth and clean, remove the rag and insert the new thermostat.
Tip: make sure the thermostat is installed with the spring facing down.
Apply a light coating of sealing compound to the gasket and fit it, together with the housing, back in place.
Replace and tighten the housing nuts, reconnect the radiator hose and top up the radiator with coolant.
Tip: tighten the housing nuts alternately and equally to avoid damaging the housing.
Where to get a new thermostat in Cape Town
Now that you know how to replace the thermostat on your car, you’ll need to get a new thermostat.
Masterparts is a key supplier of quality motor vehicle spares and parts, including a range of thermostats manufactured from anti-corrosive materials.
All our thermostats are tested and calibrated to ensure optimal functionality.
They’re available at branches located across the greater Cape Town area, Durban and Windhoek.
Masterparts stocks a comprehensive range of high-quality parts for almost all vehicle models – old and new – on our roads. Contact us if there’s a part you need and we’ll be happy to help.
