Fan clutch how does it work

When this occurs the fan clutch must be replaced. If you have any questions about a fan clutch, please visit our forum. If you need car repair advice , please ask our community of mechanics who are happy to help.

Home Articles Fan Clutch. How Fan Clutches Work. Your engine will overheat if not for the fan clutch A fan clutch is attached to the front of an engine on rear wheel drive cars and trucks only. However, non-thermal clutches are a lower-cost option than thermal-style clutches. The thermal fan clutch operates in response to underhood temperatures.

As hot air blows across the radiator, it heats a thermal spring mounted at the front of the clutch. As the spring is heated, it turns and allows valve ports to open within the clutch. Silicone fluid stored inside a reservoir is allowed to pass through these open ports and enter the working area of the clutch. This engages the clutch and drives the fan. Once the engine is cooled down, the thermal spring rotates back and closes the valve ports, disengaging the fan.

The speed at which a thermal fan clutch spins a fan depends largely on the exact fan you choose. Standard-Duty Thermal Fan Clutch : This design turns the fan at percent of the water pump shaft speed when engaged, and percent when disengaged. Heavy-Duty Thermal Fan Clutch : This fan style turns the fan at percent of the shaft speed when engaged for increased cooling.

When disengaged, it turns the fan at percent. Severe-Duty Thermal Fan Clutch : Severe duty thermal fans turn the fan at percent of the shaft speed when engaged and percent when disengaged.

These variables are manufacturer-specific and fan speed is dictated based on the level of cooling required. These problems are often caused by a bad bearing, which may be seized or have excessive play, or by a worn or loose thermal spring.

Armed with this information, you can identify a bad fan clutch and replace it with the proper aftermarket option. Are you saying that, if you grab a fin and try to spin the fan but it stops very nearly as soon as you let go of it, the clutch is bad? It should stop spinning relatively quickly—but if, after the engine has stopped, it just spins and spins, then it points to a problem with your fan clutch.

Is it ok to use a heavy duty fan clutch when a standard is normally used or came from the factory? So my question is. I have changed out my fan clutch 3 times already and my car is still over heating?

Changed it out again this past weekend stopped over heating but now less power? Then this morning started up had the power it should but once again started to over heat!! Please help me!! What is wrong with my car??

Its a Oldsmobile bravada. Do you think there could be another reason your engine is overheating? What is the age of the coolant? Has the radiator been flushed within the last 4 years?

Was the thermostat replaced in the last 4 years? When the engine is cold, the clutch is essentially disengaged, which is why the fan runs at its slowest compared to the engine's speed. As the engine warms up, the air flowing to the fan assembly becomes hotter. The hotter air causes the thermostatic spring to unwind and open the valve. Silicone fluid from the reservoir chamber flows into the main chamber, engaging the clutch, and the fan spins faster though it's still slightly slower than the engine.

A broken or weakened thermostatic spring in the clutch hub cannot be replaced or repaired. Silicone fluid oozing past the bearing seal means the clutch must be replaced. To confirm the diagnosis, start with this simple test: Spin the fan as hard as you can on an engine that has not been started that day.

If the fan rotates more than five times, you can bet the clutch is bad. You should feel some resistance and the fan may spin up to three times, depending on the ambient temperature. But even if it rotates three or fewer times the clutch could still be bad. You need to do more tests. In these vehicles, the silicone fluid doesn't drain back overnight, so the fan may barely spin on a cold engine.

It could take a brief drive to get it to declutch. If your fan clutch is not operating the way it should, it's likely due to a fluid leak or a bad thermostatic spring or valve. When a leak occurs, it's at the bearing seal, at the center rear of the clutch. Run your finger around the joint and if you get a big dollop of black goo, that's silicone fluid that has leaked from the housing. Replace the fan clutch. A light smear of silicone fluid could be normal seepage--no seal is perfect.

Obviously, if a substantial amount of fluid is missing, the clutch won't spin as fast as it should. As for the other potential culprit, most failing thermostatic springs open the valve too soon.

On the other hand, failed valves that stick closed result in low fan speeds and little cooling. Let's say spinning the fan didn't reveal a problem, there's no leak and you think the spring is okay. You could still have a bad valve. Here's how to find out. You can't use an infrared thermometer because it will read the temperature of a nearby surface, which could be very different from the air temperature. Find a joint in the fan shroud with enough flex to let you insert the probe without getting it in the path of the fan.

If necessary drill a small hole in the shroud. Run the engine at fast idle. Check the engine temperature gauge or your scan tool. If it's a hot day, the coolant temp will rise.