Hi everyone, i own a lexus ES 300, 2003 model with 264,000 miles on her. Just recently the temperature guage started to exceed half mark. I use toyota recommended coolant and i have no idea what the problem is. I live in Nigeria where the practice regarding car cooling systems that seems normal to everyone is once a car comes into the country the thermostat is removed and the fans are connected to ignition with a relay so it runs continuously so long as ignition is on and the coolant runs into the engine to cool it irrespective of the engine temperature. The mechanics here believes the temperature at the tropics, Sub-Saharan Africa, is not suitable for the operations of a thermostat and hence would result in the car engine running hot and overheating.

One day i drove a short distance in a hot afternoon, i opened the hood and saw my upper radiator hose is swollen and hard but the temperature is at the half mark. Next day driving, it was going up towards the red danger zone and i had to off the engine. I opened the hood and the coplant reservoir is boiling like a pot of water on heating and overflowing, spilling on the ground till the radiator is empty
I got another coolant in there and drove again same thing happened. I called a mechanic and he said i have to take out the thermostat and run the fan straight to ignition with a relay. I figured that might be the only option so the car can move without damaging the engine. I got them to do it for a little token, the fans will come on once the ignition is on until the ignition is off and the temperature guage is showing cool, hardly up to the half mark.

I got home with the thermostate, put it in a pot with water and started heating it. The thermostat opened as the temperature got to boilimg point and closed as i took it into cold water, I guessed it was okay.

I am plannimg to return my car cooling system to default settings with a new thermostat in place but i am not sure what the problem is. My closest guess is that maybe the thermostat is opening at a higher temperature other than 82 degrees celcius for which it is rated and is causing the engine to run hot. So are there thermostats with lower temperature rating, say 60 or 70 which i can use? I am aware of the diadvantages of this setup on the engine efficiency and i want to revert to factory settings.

 

Hello,

Did overheating issue stop when the Thermostat was taken out and Fans were bypassed? They did two vital actions simultaneously, so now you need to work out which of those mods actually helped in your situation.

If you are sure that the thermostat is working, try wiring the fans back as they were from the factory, while leaving the thermostat out, as it will be an easier option than going vice-versa. Check if that will change anything, if your car would continue running fine, you have something up with a thermostat, the issue may be that it doesn't allow enough fluid to circulate, creating a bottle neck in the system. If the heat in your area is enough to overwhelm the factory system, then you are probably fine leaving the thermostat out, you won't get any efficiency loss.

With that, if returning fan configuration to stock would cause the car to overheat, there may be an issue with the fan control system. In that case, while the fans are still wired as stock, check that the FAN NO.1 Relay clicks in when the car begins to overheat, if not, something doesn't trigger the fan, it can be a Temperature Switch located in the bottom of the radiator, see if it has continuity once the car is hot.

Hope this helps and best of luck!