Last month I went at Mitsubishi dealer for the maintenance revision. My car had the coolant replaced and a cat back installed. Ever since, I noticed that the engine fan stays working a lot more time than the habitual, like the temperature of the engine was too high.
Today I reseted the ECU and went for a ride... unfortunately the engine fan stays working too much time as before. I stopped my car in the garage and the engine fan stayed working at least 5minutes and I gave up and turned off the key.
I'm becoming crazy, trying to find out what is happening.
My thoughts: (just guessing)
Engine running too lean due to cat back exhaust
Engine running hot due an improvement in power
Bad coolant replacement, maybe air in the system. Is there a bleed valve?
Lambda sensor not working properly
Coolant sensor with problem.

Any help I would appreciate

 

That's weird I have a magnaflow Ti cat back and I don't have that problem. Take it in for a checkup.

 

Has the air temps in the region that you are living in gone up? If so that may be why the fan is staying on longer, also if you are using you a/c that may be a reason. Aso for your guessing the thermostat controls the temperature of the engine. It usually will run approx 190-200 degrees, running lean or improvement in power wont affect this. Get your hands on a datalogger and watch the actual ECT temps your gauge on the dash is not exact, then go from there

 

Cat back wont affect ect that much. if your fan stays on 5 min something else is wrong. speede is right, watch your ect temps with the fan on...if it is not going down by a degree every couple seconds something is wrong...unless you live where the temp outside is 150 degrees. My guess is they f-ed up the coolant since thats what they messed with.

 

My fan goes on for for 10 sec and then off for 5 sec and then on again for 10 sec when I first turn on my car. Does this for at least five minutes. I always turn the car on and I let it run before leaving the house. I go back in and brush my teeth then I have to move my car in the alley, park and close the gate behind me. The fan is on again off again the whole time. I don't think it continues after I've been driving. Haven't used A/C in a long time.

I always thought it was part of the Evo's charm. I like the fan

 

my fan runs alot too.......when i start my car and let it warm up it starts to run about 30sec after i start my car, then it will run for about 10sec off for 5 sec and it will do that over and over ontill i start to drive!?!?!?!

i have a 03 and it has been in for the recall. I went back and the dealer said it was normal!!?!?!

 

It might be the fan relay. Have them check it out. That caused my fan to be on as soon as I idle. If its under warranty, they will fix it for free.

 

where are your climate controls at?? if your controls are in the DEFROST mode, it will automatically kick the AC on and activate the fans. it will cycle, as xphillipjrx described, even without pushing the AC button. the AC activates and acts as an air dryer for the windshield to dry the air and defrost the windshield. most American cars are the same way. if your controls are not in the defrost position, then you may have a faulty circuit at the fan controller on the fan or the fan switch that is usually in the radiator or the thermostat housing. good luck....