New Fan clutch, junk out of the box?

[mbrummal]

A fan clutch "locks in" when the radiator is at 195/210 degrees. Fan clutches free wheel at normal engine operating loads and temps.....If you increase the engine load or restrict the air flow,the radiator increases in temp until the thermostat is open all the time. At that point the fan clutch will lock in,and increase air flow to cool the radiator,and the engine.... To put it another way, you need to stress or max out the cooling system to test a fan clutch

No you don't. If it is bad it still won't cool the engine under normal operating conditions.

 

[xengineguy]

Read the post a few more times, Not tring to BS anyone!!! Just help people understand...Like I said read it again.

 

[MUSKYMAN]

A fan clutch "locks in" when the radiator is at 195/210 degrees. Fan clutches free wheel at normal engine operating loads and temps.....If you increase the engine load or restrict the air flow,the radiator increases in temp until the thermostat is open all the time. At that point the fan clutch will lock in,and increase air flow to cool the radiator,and the engine.... To put it another way, you need to stress or max out the cooling system to test a fan clutch

Sorry you are wrong.

These clutches are never supposed to "lock in" they become more positive as the air temp increases and less positive as it cools in a range based on the viscous fluid in the clutch.

When they sit the fluid settles to the bottom and causes them to be much more positive and thats when they roar at start up. once the rotational forces work on the fluid it flows back out evenly and the clutch becomes less positive and starts to work correctly.

If the engine rpm increases past a point the same rotational forces push the fluid out farther and the clutch releases even more so the that the fan is not spun at too high of a rpm. when they are spun too fast they can cause the fan to explode and that can cause damage to the hood as well as all kinds of other things under the hood.

Another way they fail is they just stop cooling the engine even under light driving conditions. This is the most common and it will often show it self first at low speeds under load like in sand. A new clutch will often fix the situation right off.

so no...they do not "lock-in"

 

[xengineguy]

Did you see the "" "" around "lock in " ? You are correct the clutch does not LOCK to the hub ! I used that term to simplify the post.
Muskyman is correct about the fluid settling to the bottom of the clutch and that is what causes the roar for a short time after cold start.
After that your lost, RPM is not what causes a thermo style clutch to work.(the type used by most OE including land rover).
A simple viscous clutch is not what I was describing....

If your cooling system is in good shape a thermo style fan clutch will not engage under light loads....70 degrees OAT 65 MPH flat land . If you don't believe it, ask the people that use electric fans.

Why do you guys think OE put fan clutches on cars and trucks? To reduce engine noise at cruse speeds and increase MPG !

 

[mbrummal]

Read the post a few more times, Not tring to BS anyone!!! Just help people understand...Like I said read it again.

I'm sorry. Maybe I should have specified what I was objecting to. I was referring to your last statement: "To put it another way, you need to stress or max out the cooling system to test a fan clutch." That is wrong. They will fail and not keep the engine cool in easy/non-stressful situations.

Did you see the "" "" around "lock in " ? You are correct the clutch does not LOCK to the hub ! I used that term to simplify the post.
Muskyman is correct about the fluid settling to the bottom of the clutch and that is what causes the roar for a short time after cold start.
After that your lost, RPM is not what causes a thermo style clutch to work.(the type used by most OE including land rover).
A simple viscous clutch is not what I was describing....

If your cooling system is in good shape a thermo style fan clutch will not engage under light loads....70 degrees OAT 65 MPH flat land . If you don't believe it, ask the people that use electric fans.

Why do you guys think OE put fan clutches on cars and trucks? To reduce engine noise at cruse speeds and increase MPG !

What Muskyman describes is a secondary function of the fan clutch. The fan is never going the same speed as the water pump because it is a viscous drive. If the fan was to go at whatever rate the water pump is turning at with the engine at 5500RPM (the rev limit on my truck) the fan would most likely explode and take some vital stuff with it. The viscous drive will prevent the fan from ever reaching that speed especially if it is free-wheeling because the radiator is already cool from the airflow of moving a a pretty good pace.
If you want to get technical, this is how the fan clutch works:

The viscous fan provides a means of controlling the speed of the fan relative to the operating temperature of the engine. The fan rotation draws air through the radiator, reducing engine coolant temperatures when the vehicle is stationary or moving slowly.

The viscous fan is attached to the coolant pump drive pulley and secured to the pulley by a nut. The nut is positively attached to a spindle which is supported on bearings in the fan body. The viscous drive comprises a circular drive plate attached to the spindle and driven from the coolant pump pulley and the coupling body. The drive plate and the body have interlocking annular grooves with a small clearance which provides the drive when silicone fluid enters the fluid chamber. A bi-metallic coil is fitted externally on the forward face of the body. The coil is connected to and operates a valve in the body. The valve operates on a valve plate with ports that connect the reservoir to the fluid chamber. The valve plate also has return ports which, when the valve is closed, scoop fluid from the fluid chamber and push it into the reservoir under centrifugal force.

Silicone fluid is retained in a reservoir at the front of the body. When the engine is off and the fan is stationary, the silicone fluid level stabilises between the reservoir and the fluid chamber. This will result in the fan operating when the engine is started, but the drive will be removed quickly after the fan starts rotating and the fan will 'freewheel'.

At low radiator temperatures, the fan operation is not required and the bi-metallic coil keeps the valve closed, separating the silicone fluid from the drive plate. This allows the fan to 'freewheel' reducing the load on the engine, improving fuel consumption and reducing noise generated by the rotation of the fan.

When the radiator temperature increases, the bi-metallic coil reacts and moves the valve, allowing the silicone fluid to flow into the fluid chamber. The resistance to shear of the silicone fluid creates drag on the drive plate and provides drive to the body and the fan blades.

They progressively "lock in" based on the temp of the air flowing through the radiator. It isn't a set temperature of 195/210 degrees.

 

[Quentin]

Interesting. I always thought that LR used a waxed based fluid in the viscious unit.
Nice to findout exactly what it is

 

[ptschram]

Fan clutches are listed in the vendor's for sale section.

I've got a small pile of them for most Rover engines, including the diesels and the BMW engine.

 

[xengineguy]

They progressively "lock in" based on the temp of the air flowing through the radiator. It isn't a set temperature of 195/210 degrees

No No Please read your post:

A bi-metallic coil is fitted externally on the forward face of the body. The coil is connected to and operates a valve in the body. The valve operates on a valve plate with ports that connect the reservoir to the fluid chamber. The valve plate also has return ports which, when the valve is closed, scoop fluid from the fluid chamber and push it into the reservoir under centrifugal force.

The bi-metallic coil reacts to heat! Most are between 195/210 degrees.... The coil turns a rod that changes the fluid flow/placement in the clutch. Not RPM based !

The thermo or non-thermo will slip at high rpm because of torque limits of the clutch.. ( Not rpm limited...)
When fan rpm goes up,so does the torque required to drive it.

 

[mbrummal]

No No Please read your post:


The bi-metallic coil reacts to heat! Most are between 195/210 degrees.... The coil turns a rod that changes the fluid flow/placement in the clutch. Not RPM based !

The thermo or non-thermo will slip at high rpm because of torque limits of the clutch.. ( Not rpm limited...)
When fan rpm goes up,so does the torque required to drive it.

I was saying it isn't a set temperature of 195/210 that you claim it is. I never said it wasn't temperature based just that it wasn't as specific as you made it out to be.

 

[p m]

By the way...
The fan clutch is controlled by the temperature of air passing through the radiator.
Bad thermostat (stuck closed or halfway open), bad water pump, and clogged radiator will all lead to reduced flow of hot air to the fan clutch, which will make the matters worse.
The fan clutch is the easiest thing to troubleshoot, though.

 

[xengineguy]

PM is correct! In the original post, Mike 26 describes a new clutch on an engine "at operating temp". I was attempting to explain that just because the engine is at operating temp,the clutch will not "engage" (Lock in) until you increase the temp of the radiator...... And if the normal engage or "lock in" temp isnt 195 to 210 what is it???
I would never say a fan clutch progressively "Locks in". Just not the way it works....When you hear a good clutch, working correctly, they engage and disengage quite quickly .... (the run time of the clutch depends on the temp of the radiator)