Engine fan running all the time (is that normal)

[jasonsuperb]

My 2004 montero gen 3 radiator belt driven Fan runs all the time even when the engine is cold. Is that normal? I’m trying to determine if something is wrong with it and could be the cause of my poor mpg and now that the weather is cold my heater is weak. I’m thinking if the fan is running when it shouldn’t be it takes longer for the engine to warm up effecting the efficiency and heater.

I’ve been getting as low as 10 mpg on my 7 mile commute back and forth. Have done tune up and trans flush already which made no difference. Truck only has 107k miles.

Thanks!


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[Rambo Penguin]

Sounds like your fan clutch is broken. It should click on and off at operating temp.

 

[Salonika]

What did the « tune up » include? Got a check engine light on? Any codes? I wouldn’t think the fan would make the warmup take much longer since the thermostat really controls that.....it would just stay closed and the engine would still warm up.

 

[jasonsuperb]

Sounds like your fan clutch is broken. It should click on and off at operating temp.

When it (clicks) off does the fan completely stop moving or does it just kind of free spin? When the vehicle is first started up should the fan be spinning? When the engine is off I can manually spin the fan, it’s not locked in place.


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[jasonsuperb]

What did the « tune up » include? Got a check engine light on? Any codes? I wouldn’t think the fan would make the warmup take much longer since the thermostat really controls that.....it would just stay closed and the engine would still warm up.

No check engine light. Tune up was plugs and wires. Valve cover gaskets. Tranny flush. Coolant flush. Timing belt. Water pump.


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[jeep-N-montero]

Google "how fan clutch works" and it will explain everything, the function is not specific to Monteros.

 

[Salonika]

Maybe you have a brake caliper dragging. Drive around a bit then stop in a parking lot, hop out and feel each wheel with the back of your hand. If you have a dragger, it’s easy to find as it will be noticeably warmer than the others. Otherwise as I said before, you may have a fan clutch problem but I’d say that’s unrelated to a mileage or engine warmup problem.

 

[offthepath]

Are you asking if the fan should ever stop moving while the engine is running?

If so than no, any time you look in the engine bay the fan will be turning. It uses a thermal clutch fan. When cool, even through the fan is turning, the clutch is not locked and it is turning fairly slow. As it warms up the clutch locks making the fan spin much faster and moving more air. It is not like an electric fan that is either turning or not. Id check the thermostat first. It may have failed and is stuck in the open position.

 

[jasonsuperb]

Maybe you have a brake caliper dragging. Drive around a bit then stop in a parking lot, hop out and feel each wheel with the back of your hand. If you have a dragger, it’s easy to find as it will be noticeably warmer than the others. Otherwise as I said before, you may have a fan clutch problem but I’d say that’s unrelated to a mileage or engine warmup problem.

I thought about this as well. The front wheels are always much warmer than rears but I had the rotors and pads replaced at the dealer at the same time as tune up and no difference there. Also the mpg is much better on longer trips so I don’t think it’s the brakes.


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[jasonsuperb]

Are you asking if the fan should ever stop moving while the engine is running?

If so than no, any time you look in the engine bay the fan will be turning. It uses a thermal clutch fan. When cool, even through the fan is turning, the clutch is not locked and it is turning fairly slow. As it warms up the clutch locks making the fan spin much faster and moving more air. It is not like an electric fan that is either turning or not. Id check the thermostat first. It may have failed and is stuck in the open position.

From what I found online searching if the fan clutch is stuck on you can’t turn it by hand when the engine is off. (Mine spins freely) and if it’s broken in the off position you will over heat. I don’t. So I’m guessing my fan clutch is working as it should and my issues must be somewhere else. I did some thermostat tests I found online to check it and it seems to be working as it should as well. I think either my heater core is partially plugged or there is an air bubble somewhere, the radiator is showing full. Both coolant lines through the fire wall are hot but not scalding hot. But my heat in the cab isn’t hot enough and only coming out of the left vent. Other vents are cool. Still can’t figure out what’s causing my low mpg in short drives.


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