Engine gets hot only during very hot days

2005 MITSUBISHI LANCER
70,000 MILES
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OMSHANTI12
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This is 2.0 engine and automatic transmission ES model
Replaced radiator two years ago, O2 sensor just replaced.

Never gets hot during normal summer temperature or in winter. Just gets hot after humid and very hot days only.

Noticed fan do not run after shutting engine shuts off even after long drives. VS to run until it cool down coolant.
would Appreciate input.
Jun 29, 2017 at 1:54 PM
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STEVE W.
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Which engine, transmission and sub-model of Lancer please. Different wiring and controls for the two engines and transmission. Thank you
Jun 29, 2017 at 2:48 PM
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OMSHANTI12
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thanks Steve, It is a 2005 ES 2.0 engine.
Jun 29, 2017 at 3:06 PM
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OMSHANTI12
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It is an automatic transmission.
Jun 29, 2017 at 3:07 PM
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STEVE W.
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Well looking at the wiring and it appears that it should stay on while the engine is hot. I suspect either the fan control module or the ECT sensor.
The best way to find out which is the problem involves using a high level scan tool to activate the fan through the ECM. That will test the complete circuit and let you see the ECTs actual data. Start with a cold engine, then run it up to temperature and see what it reads, plus you can see when the ECM commands the fan on/off once it is warm.

Jun 29, 2017 at 3:50 PM
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OMSHANTI12
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what name of tool do i need ? How expensive could be ?
Jun 29, 2017 at 4:34 PM
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STEVE W.
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The scan tool that would work to do the tests is not cheap. It would be much cheaper to have a dealer do the testing. The actual scan tools used for this level of testing cost between $3,000.00 US to over $14,000.00 US.

What you could do is replace the coolant temperature sender and see if it is better. If not change the fan controller. Or take it to a shop that has a good scan tool.
Jun 29, 2017 at 7:37 PM