DIY Thermostat replacement

The thermostat is located in the cooling circuit of your 4x4. It works as a "valve" which opens according to the temperature of the coolant. It is a key component of the cooling system.

To enable the engine to warm up to the correct operating temperature, the thermostat prevents coolant from circulating through the radiator until it reaches a certain temperature.

When you notice that the engine temperature doesn't reach or is higher than its initial temperature during operation.

There are 2 possible types of problem:

- If the calorstat remains blocked in the open position, the engine can't reach its normal temperature because the coolant is not heated. This can lead to higher fuel consumption overconsumption and / or the heating taking much longer than normal to warm up.

- If the calorstat remains in the closed position, the coolant will not circulate towards the radiator. This will cause the engine to overheat which in turn  can result cylinder head gasket failure, warped cylinder head or even engine failure.

In this article, we explain step by step how to easy it is to replace the thermostat on your 4x4.

We used a Toyota HDJ 80 for this article .

To replace the thermostat on your 4x4 you require the following tools:

- 12mm flat or socket spanner

- Flat pliers

- Emery cloth

- Silicone sealant

To give you an idea of the difficulty level of our tutorials, we note them from 1 to 5.

Replacing the thermostat on a 4x4 is a level 2 job.

1 - This HDJ80 doesn't have the air-con option so there was no compressor to get in the way. If you do have air-con, access is a little less straightforward but it is also possible with a little more time.

For ease of access, remove the return hose from the cooling circuit.

2 - The thermostat housing is located on the side of the engine block. Undo the 2 bolts that hold the cover in place. 

3 - Now you can easily remove the old thermostat, along with the rubber seal.

4 - Remember to clean up the two surfaces (thermostat housing cover and engine block) with a rub of emery cloth to ensure a good seal.

Position the gasket correctly on the thermostat and then place it in position. with the side with the holes facing upwards.

5 - Now bolt the cover back into place.

Be sure to top-up the coolant and run the engine to bleed out any air. On the Toyota HDJ80 you just need to remove the radiator cap whilst running the engine to bleed the cooling circuit.

PS. You can use a dab silicone sealant but the rubber seal is normally good enough to seal the housing to the block. 

THERMOSTAT

Credits - thanks to Association Sportive Mantaise  - blog.asm4x4.com

Please note: Euro4x4Parts publishes this information to help its customers but cannot be held responsible for the advice given here and practical consequences therin.