Radiator fan constantly running. 1998 GMC K1500 Suburban Vortec 5.7

[BC K1500]

I just recently realized that my radiator fan is constantly running. It runs on full speed no matter if the engine is ice cold, hot or anywhere in between.

Anyone has experience whit this problem?
What are the troubleshooting steps to figure out whats wrong?

Thank you.

 

[Schurkey]

Either the fan clutch has seized and is in need of being replaced; or you're not used to a fan clutch--that spins the fan even when unlocked. They're not like an electric fan, where the fan is motionless until the electric motor engages.

If the fan can be turned with one finger while the engine is "off", it's probably fine. If you shut off the engine while fully-warm, the fan will probably spin for a second or two after the engine stops.

If the fan can't be turned with one finger, you need a new clutch. You'll welcome the dramatic reduction in noise, and probably improved fuel economy. Might want to verify the belt hasn't been slipping from the drag of the locked clutch, too.

 

[454cid]

I just recently realized that my radiator fan is constantly running. It runs on full speed no matter if the engine is ice cold, hot or anywhere in between.

Anyone has experience whit this problem?
What are the troubleshooting steps to figure out whats wrong?

Thank you.

Do you mean the electric fan on the front of the "radiator" for the AC?

 

[BC K1500]

Either the fan clutch has seized and is in need of being replaced; or you're not used to a fan clutch--that spins the fan even when unlocked. They're not like an electric fan, where the fan is motionless until the electric motor engages.

If the fan can be turned with one finger while the engine is "off", it's probably fine. If you shut off the engine while fully-warm, the fan will probably spin for a second or two after the engine stops.

If the fan can't be turned with one finger, you need a new clutch. You'll welcome the dramatic reduction in noise, and probably improved fuel economy. Might want to verify the belt hasn't been slipping from the drag of the locked clutch, too.

The fan can be turned when the engine is off. However, the fan is blowing like a tornado even when the engine is cold in cold weather.

I was not familiar whit fan clutches before posting. I did some googling and if I understand this video correctly I have a bad fan clutch;

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It seems like there is nothing else can cause this but a faulty clutch.
Please correct me if I'm wrong.

Thanks

 

[BC K1500]

Do you mean the electric fan on the front of the "radiator" for the AC?

I do not have an electric fan in front of the AC radiator.
The AC condenser sits just in front of the engine radiator.

 

[454cid]

I do not have an electric fan in front of the AC radiator.
The AC radiator sits just in front of the engine radiator.

It's proper name is condenser.

 

[BC K1500]

It's proper name is condenser.

You are right, thank you for the correction.

 

[Schurkey]

BE CAREFUL.

If you are not familiar with fan clutches, it's easy to think they're engaged and blowing hard when they're NOT.

Many folks have NO IDEA how much air a fan and clutch will move when the clutch is engaged.

IF (big IF) you can have a conversation with other people inside the vehicle with you while driving at highway speed...the fan clutch is not engaged. A seized fan clutch will make so much noise you won't be able to hear yourself think.

First Guess: There's not a thing wrong with your fan clutch. That video is overly-simplistic. A disengaged "regular-duty" fan clutch will still spin the fan at ~30% of water pump speed, which tends to be higher than engine speed due to pulley ratio between crank pulley and water pump pulley. When fully engaged, the fan spins about 70% of water pump speed. 70% of water pump speed will make a hell of a noise, and enough air flow that you'll see Dorothy and Toto fly past.

"Heavy-Duty" and "Severe-Duty" fan clutches spin the fan at higher percentages when disengaged, and higher percentages when engaged. When used with a "standard duty" fan, a Heavy-duty or Severe-duty fan clutch won't ever disengage properly. They need the extra drag of an extra large or high-pitch fan to disengage them; and as said--they still spin the fan faster than a standard-duty clutch.

 

[BC K1500]

BE CAREFUL.

If you are not familiar with fan clutches, it's easy to think they're engaged and blowing hard when they're NOT.

Many folks have NO IDEA how much air a fan and clutch will move when the clutch is engaged.

IF (big IF) you can have a conversation with other people inside the vehicle with you while driving at highway speed...the fan clutch is not engaged. A seized fan clutch will make so much noise you won't be able to hear yourself think.

First Guess: There's not a thing wrong with your fan clutch. That video is overly-simplistic. A disengaged "regular-duty" fan clutch will still spin the fan at ~30% of water pump speed, which tends to be higher than engine speed due to pulley ratio between crank pulley and water pump pulley. When fully engaged, the fan spins about 70% of water pump speed. 70% of water pump speed will make a hell of a noise, and enough air flow that you'll see Dorothy and Toto fly past.

"Heavy-Duty" and "Severe-Duty" fan clutches spin the fan at higher percentages when disengaged, and higher percentages when engaged. When used with a "standard duty" fan, a Heavy-duty or Severe-duty fan clutch won't ever disengage properly. They need the extra drag of an extra large or high-pitch fan to disengage them; and as said--they still spin the fan faster than a standard-duty clutch.

Thank you for taking the time to educate me about fan clutches.

Reading your excellent write up I concluded that the fan clutch is indeed working properly.
I didn't know that the fan always supposed to run at least 30% at all times.
This car had the factory tow package so I would assume it has at least a heavy-duty fan clutch hence me thinking its blowing too much.

You have saved me an unnecessary repair that wouldn't have fixed anything.

Thank you again!!!

 

[Schurkey]

You're welcome. One of the many services I offer.