98GS400 Overheating issue

[skee]

Whether A/C is on or off, if driving in slow traffic engine temp begins to rise and will cool down if maintain a speed of around 60. IF its a hot day 75 or above even at 60mph temp raises way above normal but not overheat. I did check to see if the coolent was pumping through the hoses and it is(if that means anything). I also notice the fans run contineously from time i start the car. A lexus tech said that the temp guage was rising because the fans are on constantly so the engine thinks it is running hot. I know the car is fly by wire. But can the overheating or temperature rising on the temp guage be due to the fan sensors being bad? (I need to just get a shop manual)

As in my other thread im changing the timing belt so while i am there i am changing the waterpump. What else should i check to resolve the overheating??

 

[stevechumo]

The statement about the Lexus tech said isn't correct. I don't know where he got that idea from. Did he graduate junior high school? LOL. Anyway, the ECU detects the temp. from the sensors and if the sensors read cold, then it'll send the cold signal to the ECU. And the temp gauge will show what it reads. Even if you put in 2 more fans and make the coolant temp cooler, then it'll show cooler.

It seems like you might have a bad sensor. Usually, there'll be 2 sensors. 1 is at the bottom of the radiator. And the other is on the front water bridge below sparkplug wires. You'll need to remove the square-like tube that covers the sparkplug wires crossing to the other bank to see it. But if there's a bad sensor, usually the coolant indicator light will come on. But who knows?

When the engine runs, the coolant in the reservoir should be sucked immediately back to the engine, but slowly. That's a good sign of the good water pump. If the engine is cold, the coolant in the reservoir must go back to as it was on the same level as it's cold last time. If it's not, then you must have a leak somewhere. Leaking will cause the temperature to go up.

Also, the heating could cause by the bad thermostat. It doesn't open soon enough to allow trapped hot coolant in the engine to go to the radiator. Try to change the thermostat first to see if it helps. You can use an aftermarket one. No need to use OEM stuff.

The last thing that could happen is you have a blocked radiator.

With good working OEM fans, sensors, and there's no leak. The temp gauge shouldn't go up even if you're around 90-100 degree.