by all means i can not recommend YOU a DIY to open the hood and check here & there, being a Girl as your name suggest, a heat injury is no., Please do not attempt a DIY
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you can goto Toyota 3S shop specifically ask them to check for:
- If radiator cap is working
- if the radiator fan is running on automatic
- if the cooling system is working good by checking onto hose pipes the Top one shall be bone hard when engine is hot and running. If it is HOT soft & collapses upon pressing softly - the thermostat valve is stuck open and vehicle engine is not reaching its optimum temperature to turn off the cluster light.
- if you are using normal tap water out there, most likely thermostat valve has corroded and STUCK OPEN.
ask the shop to replace thermostat valve with a new one ( you shall take old one from them ) and refresh the cooling system with Coolant top up radiator & expansion bottle ( plastic one connected to radiator )
it may cost you in tune of 200 - 2000 for parts & coolant & approx 2000 for labor charges.
plus you can enjoy the look at the service supervisor face when asking him to do the 4 above point, and that will be priceless.