I thought a fan clutch was supposed to stay mostly still until it got hot from the radiator, then it would start spinning based on your RPMs.
I thought my old fan clutch was broken because it was just as hard to spin when you first start the Jeep as it was when climbing a long hill in 4LO slowly—maybe it would turn a quarter of the way if you were lucky.
I bought a new one, and it does the same thing. I just installed it, and the fan started spinning really fast right away after the Jeep sat for 6-7 hours. When I press the gas, it speeds up, and when I let off, it slows down. I don’t understand why it’s doing this.
If the new fan clutch spins like this when the engine is cold, why even have a clutch? It seems like it’s acting just like a regular fan driven by the belt. Unless the new one is also faulty, I don’t get it.
A fan clutch is a part of your car’s cooling system that controls the radiator fan. When the engine is cool or at a normal temperature, the fan clutch allows the fan to spin less, saving power. If the engine gets too hot, the fan clutch fully engages the fan, making it spin faster to help cool the engine.
Most fan clutches use a type of fluid coupling with a temperature-sensitive system, similar to a thermostat. They are usually reliable, but if they fail, you might notice your engine overheating when idling. A bad fan clutch can also make the air conditioning less effective since the fan helps cool the air conditioner’s condenser. In cold weather, a failing fan clutch might cause the heater to blow only lukewarm air instead of hot air.
The viscous clutch always lets the fan spin, but it adjusts how fast it spins. As the clutch heats up, the fluid inside it gets thicker, which makes the fan spin faster. When the clutch cools down, the fan slows down but still keeps spinning.
If you’re not sure, you can check it yourself. Try turning the fan by hand when the engine is cold, and then try again after you’ve driven for a while. You should feel a difference in how hard it is to turn the fan.
If your fan is always running at full speed, there might be an issue.
Mine sometimes speeds up and slows down in the morning, but after driving half a block, it slows down. I only hear it loudly again if I’m stopped at a long red light or in a drive-thru. After a short distance, it goes back to low speed.
To be clearer:
If your Jeep is cold (after being parked overnight), is the fan very loud?
If you’ve driven half a mile, is the fan still loud?
If your Jeep is at normal temperature (around 210°F), is the fan still loud?
If the answer is yes to all these questions, something might be wrong. The fan shouldn’t be running at full speed all the time.
Even if the fan clutch is working correctly, it’s normal for the fan to spin at full speed and make a loud noise for a few minutes after you start the engine. This happens because the viscous fluid in the clutch settles overnight or over several hours. This could explain why the fan clutch feels the same whether the engine is cold or hot—the clutch might be in its “tightened up” state in both cases.
After driving for a few minutes, the fan clutch usually “loosens up” and the fan won’t spin at full speed unless needed.
If you start a cold engine, drive for half a mile, then stop and turn off the engine, and spin the fan by hand, it should feel noticeably looser.
I’ve noticed the same thing. My fan spins just as easily when it’s cold as it does after driving 25 miles home from work. When I spin it by hand, it turns about a quarter to half a turn.
Yes, that’s right. I’m confused because the new fan clutch I bought behaves exactly the same as the old one, which I thought was broken. The fan is just as hard to spin by hand whether the engine is cold or hot—no difference in resistance.
The fan keeps making a loud noise in all the situations you mentioned. I thought my old clutch was stuck in the “engage” position, but the new one does the same thing.
I got it from a local Lordco parts dealer, and it’s made by Hayden. I guess I’ll return it for a different one. It’s better than having a fan that doesn’t spin at all, but the loud roaring makes it sound like a semi-truck.
Make sure the new clutch you bought is thermostatic. It should have a small spring coil in the center. Non-thermostatic clutches are flat on the front and don’t control temperature. They are made to let the fan run at full speed (3500-4000 RPM) so it doesn’t break apart.
In very hot weather, especially with the air conditioner on, your fan clutch might stay engaged most of the time. This is more likely if the radiator or AC condenser is dirty or clogged with debris, bugs, or leaves.
Viscous fan clutches should be stored standing up, not lying flat. This keeps the viscous material inside where it should be. If they are stored lying flat for too long, it can damage them. Maybe the store you bought it from didn’t know this.
Everything is clean and in good shape. The clutch has the little spring on the front and a red seal on the back that holds the fluid in. I’m sure it’s thermostatic.
I had no idea this could happen. They brought it from out back, so I can’t be sure, but I think it was probably easier to store a wide box flat instead of standing up.
At least these clutches are easy to replace, even though they’re hard to find where I live.
