What is the test for a fan clutch?

I have been searching the archives an hour now and can't find the description of what a working fan feels like hot and cold.

Just replaced the clutch fan (along with everything else in the cooling system) with a new one from NAPA and it is quite stiff to turn when the engine is cold but after a ten min. drive and engine up to operating temp. the fan is very easy to spin with engine turned off, that doesn't sound right to me. Shouldn't it be very stiff as if locked to the water pump?
Thanks,
Chris

Basic operation is that there is a viscous fluid in the head of the fan, which provides some slippage but still allows the fan to turn. There is also a clutch assembly which channels the fluid and causes the fan tension to increase (making it turn faster) when air temperature on the face spring gets to approx 170f. When the engine is cold (overnight) the fluid settles and also engages the clutch, so when you first start the car the fan will often be very loud and then quiet down immediately as the fluid is distributed, and will only engage again if the temperature on the face of the fan gets to 170f (which is really hot considering the air is coming through the radiator). The FSM tests for the fan say to put a blanket over the radiator and run the engine at 2500 RPM for ~10 minutes... you're not going to get the clutch to engage in Canadian winter regardless, and the stiffness you feel is just the constant low-drag resistance.

Like ehall said, but simplified, start your jeep and run for a minute to disperse the fluid in the fan clutch then shut it off. Turn the fan by hand. It should turn with some drag felt. Then re-start and run until up to operating temp. Make sure the hood is closed during warm-up to keep from dragging in more cold air. Shut engine off and turn fan clutch by hand again. This time you should feel more drag that the first time. If the fan clutch turns easier than the first time, when the engine was cold, then the clutch is probably bad. Sometimes you will see the fluid leaking out of the clutch which is a clue to replace.

If you have an oven thermometer and a heat gun you can probably test that way, but like I said it's unlikely to engage in normal driving in Canadian winter

ehall said:

If you have an oven thermometer and a heat gun you can probably test that way, but like I said it's unlikely to engage in normal driving in Canadian winter

Click to expand...

That's a drag since it is still over heating.

Stick a broom handle in the fan blade and start the engine if the broom handle gets kicked out clutch is good if broom handle does not move your fan clutch is bad.

Basically as described above. Here's what I do. Open the hood, have someone start it and watch the temp gauge for you, rev the engine up to 2,000 RPM, the fan should be engaged (louder/engaged/more air) cold, listen for the fan noise to get quieter (quieter/loosen/less air) within a minute or so, cover the front grille with a blanket (blocking airflow to the radiator) and wait for the engine to warm up, watch the temp gauge and when the engine is hot enough you will hear the fan clutch re-engage (louder/engaged/more air), remove the blanket, drop to idle, and let the engine cool down to normal temp before shutting the engine off. Then you know it's working. This also works to test that the electric aux cooling fan comes on when it's suppose to by blocking the airflow to the radiator.

87m6chris said:

That's a drag since it is still over heating.

Click to expand...

If you're overheating, it's not from the air being too cold for the clutch spring to engage.

Blocked radiator (feel for cold spots), head gasket, stuck termostat (upper hose is cold) air in the system, etc...

ehall said:

If you're overheating, it's not from the air being too cold for the clutch spring to engage.

Click to expand...

x2, you have issues other than a fan clutch.