Overheating... Front Fans Do Not Come On.

[o1bizzy1o]

ok one of my buddies asked me to fix his car. the problem is its overheating and the two fans infront of the radiator do not come on.

first thing i did was make sure that there was no air in the system... check

then i took off the thermostat and it looked pretty corroded and tore up so i took that out but it was too late to get a new one so one will put replaced tomorrow.

i then disconnected the fans and checked for power... theres power going to it but the fans do not come on after idling for quite a while but i do notice that it will go on when the engine first starts but that only lasts for 3 seconds and it wont come on after that.

i am thinking that the coolant temperature switch is faulty causing the fans not to kick on... but then again even when the ac is turned on the fans wont go on either... after searching the forum and google i couldn't come up with any temperature sensors for the ls400. fresh out of ideas please help.

[sha4000]

i think you are on the right track changing the thermostat which is probably the problem

[obergc]

It seems that your cooling fans might not be operating properly. You have a temp sensor in the bottom, drivers side of the radiator and there is an electrical connector near the sensor. You can check the fans for proper operation by doing the following.

1. Ignition switch On and engine temp below 181F, the fans should not run.

2. Disconnect the temp sensor at the bottom of the radiator and both fans should run high speed.

3.Reconnect temp sensor, turn A/C on and with the compressor clutch engaged and water temp below 181F, the cooling fans should rotate slow speed.

4. Raise water temp above 199F and the fans should rotate high speed.

If the fans do not rotate when you disconnect the cool temp sensor in the radiator, check the engine main relay and 30A fuse in the fuse block next to the battery, then there are 3 cooling fan relays located in a relay block behind the left headlights. Good luck.

[o1bizzy1o]

It seems that your cooling fans might not be operating properly.  You have a temp sensor in the bottom, drivers side of the radiator and there is an electrical connector near the sensor.  You can check the fans for proper operation by doing the following.

1.  Ignition switch On and engine temp below 181F, the fans should not run.

2.  Disconnect the temp sensor at the bottom of the radiator and both fans should run high speed.

3.Reconnect temp sensor, turn A/C on and with the compressor clutch engaged and water temp below 181F, the cooling fans should rotate slow speed.

4.  Raise water temp above 199F and the fans should rotate high speed.

If the fans do not rotate when you disconnect the cool temp sensor  in the radiator, check the engine main relay and 30A fuse in the fuse block next to the battery, then there are 3 cooling fan relays located in a relay block behind the left  headlights.  Good luck.

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wow great information thanks. i will give this a shot.

anyhow today i brought the lexus into the shop that im taking classes for to get my certificate. we hooked up the diagnostics and found out that the engine is running at perfect temperature. which led us to believe that the problem is within the gauge. we disconnected the temperature sensor and found out that the needle would not drop to c but one bar above... meanin gthat the gauge some how jumped a notch and reads inaccurate.. solution- replace temperature gauge?

any how the fans still dont kick on when ac is turned on. and i will have to trouble shoot the fan issue now with the information provided by obergc above. thanks your the man.

[RFeldes]

The fans will not come on until the cooling temp is high. They do not come on when you turn on the AC. There is a thread here that covers all of this. Type in "fan" and you should find it. Those fans only come on during high temp driving such as the Desert or in traffic congestion. The Lexus was designed for the world so you can see where in certain extreme locations on earth, they would be invaluable.

[sha4000]

i told a friend that on my 91ls the fans never came on and he didnt believe me i lived in baltimore at the time so i think rfields is right the condenser fan should come on when the a/c is on though

[RFeldes]

sha4000,

I was mainly referring to the ac condensor fans. They hardly ever come on, only under exterme circumstances and at startup for a few seconds. All normal on the early LS'S I don't know about the newer single fan units.