Overheating

NASER NASER

MEMBER
1998 LEXUS LS 400
V8
2WD
AUTOMATIC
169,000 MILES

Not sure if this is an overheating issue or the cluster is bad. Bought the car listed above, the cluster shows needle at zero when starting in the morning, my scanner shows that once it reaches the optimal temperature around 180-188 the needle shows 3/4 on the cluster, everything else on the cluster reads correctly. Changed thermostat and belt, bled it, temperature stable at 188, but even when I turn the ac on or raise the rpm for few minutes in trying to trigger the fan to come on it does not. Checked the sensor b the radiator, replaced it, same thing. When that sensor harness is disconnected the fan comes on, same if I disconnect the high pressure AC connector. I have heat in the cabin, now temperature is at 190 on cluster and fan still has not come on. Checked clutch fan and looks like it has been replaced. I turn it early in the morning ad it turns about 2-3 times.

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6 Replies

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

I don't think there is a problem at all with your vehicle's engine's cooling fans. In the diagrams down below I have included the operating specs. For your vehicle's engine cooling fans. I hope this helps and, please, get back to us with how everything turns out.

Thanks,
Alex
2CarPros

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Wednesday, October 23rd, 2019 AT 8:42 AM

NASER NASER

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836 POSTS

So does this mean that it may be the cluster? And does the diagram means that at 194F the fan should come on? Because I think I went up to 192 and it came back down to 180's without the fan coming on. Just raving up the motor can change the temperature either up or down.

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Wednesday, October 23rd, 2019 AT 9:33 AM

NASER NASER

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But again why isn't the fan coming on with A/C on?

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Wednesday, October 23rd, 2019 AT 10:44 AM

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

Okay, the quickest way to get the temperature to come up on your vehicle is to start it and let it idle. If you have a digital thermometer, you can point it at the top radiator hose to monitor the engine's temperature. The engine fan should come on when the temperature reaches 194 degrees. Keep in mind that the boiling point of the coolant in your cooling system is not 212 degrees. With the addition of coolant and being pressurized in your vehicle's cooling system, the boiling point is now raised to around 260 degrees. Keep an eye on the temperature gauge as well and if the engine cooling fan does not come on and the vehicle reaches the red overheating level, shut the engine off and let it cool down. It should be just fine. Please run this test and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros

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Wednesday, October 23rd, 2019 AT 11:39 PM

NASER NASER

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Yes it does reach 194 and I hear the fan run and jump out of the car to confirm and I barely catch it, because it runs for 2 seconds and goes off, and the temperature on the scanner goes down. The needle is in the same spot, 3/4 of the cluster. I am going to drive it around the block and see what happens.