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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8568
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Customer Question

r u there?
Submitted: 1 year ago.
Category: Mitsubishi
Customer: replied 1 year ago.
Hi, I own a Montero Limited 2002 3.5 L. I tried everything and the gauge still tells me that the engine is overheating. I replaced the Radiator, the radiator cap, the water pump, the thermostat, the fan clutch, even the gauge sensors and the problem remains. Is not a faulty reading, it is actually overheating. Timing belt is 3 months old. I look at diferent online forums and seems to be a common problem on this car. Do you have an answer for this?
Expert:  Doug replied 1 year ago.


I would want to check the ECU temperature and see what it is reading when the gauge says it is over heating... more often than not the vehicle is not actually over heating but the gauge is malfunctioning. It happens A LOT>

With what you have replaced if it is reading incorrectly like normal your only expectations are going to be either the cluster circuitry or the small plug in board on the bottom of the cluster. The individual gauges fail too, but are not as common. Wiring issues are not too common unless there are unusual variables (like rodent damage, problem only started after certain repairs were made, etc).

What you would want to do at this point if there is nothing suspicious with the wiring around the engine would be to pull the cluster out and disassemble it to inspect the gauge itself to make sure there is no corrosion on it or the pins etc, and inspect the circuity sheet on the back of the cluster for any damage specifically in the center of the circuitry. I am attaching a photograph of the common circuitry failure, if you look right centered in the photo you will see a lifted trace that is burnt.

If there is no damage there it is most likely the plug-in circuit board (not shown in photo, it would be on the lower right corner area of the photo though). Be aware though that when you change this part your mileage will reset to zero unless you send it out to a company like Specmo to clone the mileage over.

If the temperature on the ecu is reading high (~250F+ etc) then your only expectation for an actual over heat condition if the radiator is new/flowing correctly and the fans are both working (clutch locking up, electric fan turning on) would be a build up of gunk in the engine preventing proper dissipation. These vehicles are common to have massive amounts of scale build up in the cooling system.
Realistically though, I would suspect that you aren't exceeding an actual 225-235F range like is usually the case, and the over heat reading is inaccurate.

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