viscous clutch fan behavior

[digger]

Short Story:

When the engine gets really hot and you try spin the fan by hand with all your might how many rotations does it make?
Half rotation, 1 or several rotations?
Mine spins several rotations. It’s actually a lot stiffer when it’s cold. Is the clutch fan faulty? Didn’t notice anything leak from the box.
It's 1 month old Behr –Hella purchased new.

Long Story:

So my coolant temps have recently been increasing when the engine is sitting idling. Normally it sits at the first tick or below by a needle width or two and pretty reliably at that which is 77+/- a few degrees C (ECU reading blue sensor)

As an example this morning it was 16C outside the temps crept up to half way between the first and middle ticks in slow moving traffic and waiting at several sets of lights and quickly went down to the first tick or just below when I started moving at 70km/h.

Recently the temps have been creeping upto half way between the first and middle and ecu reading 85-90C when sitting in traffic for extended periods. If the car moves the temps come down.

I replaced my clutch with a new behr hella unit a month ago as mine was a good 8years old and started to notice the creep and assumed the clutch was to blame, if anything it got slightly worse by a couple degrees but probably the same in reality. The new unit has more resistance than the old one when cold.

I’m pretty sure previously when the engine got real hot I could hear the clutch fan whirr away when the engine was revved. Now I can’t really hear it. Pushing some thick packing cardboard into the fan was not stopping it but I only pushed it lightly as I didn’t want to damage the blades. So its not complete fubar but is it to be expected?

I have verified with infra red gun that the temps are real.

Some may say the gauge is normal but Its just not behaving as usual.

[whodwho]

When warm and not needed you can stop the fan fairly easily(not smart but I can use my finger) and actually spin it opposite direction, When needed it will engage and will not stop easily(with a rag). You should be able to hear/feel the fan pushing air when needed especially when r3ved a little

[digger]

How actually does it know when it's needed? Is there s bimetallic strip ? What to should it start working?

[AndrewBird]

At normal operating temp, the gauge should read at the middle (2nd) mark. Sounds to me like the engine isn't warming up properly. The thermostat might be stuck open. If it doesn't get hot, the fan won't lock.

[digger]

At normal operating temp, the gauge should read at the middle (2nd) mark. Sounds to me like the engine isn't warming up properly. The thermostat might be stuck open. If it doesn't get hot, the fan won't lock.

ignore the absolute gauge position just look at the relative movement of the needle as its a 75C thermostat so normally fully up to temp at the first tick. it was perfectly normal for the last 2.5yrs until last 2 months , the engine temp now gets (creeps) to 90C (just under half) if i sit long enough in traffic (even more with A/C on) when it never used to do this, when i move at speed it comes down to the first tick 78C give or take.

the radiator hoses in and out are hot.

its not cooling as well as it used to when stationary with a brand spanking new clutch fan unit. its fine on the move...and it gets plenty hot enough

im wondering if the clutch is dodgy or some other issue

[digger]

so i lie...lol, just went and let it idle for a while the fan did engage and when the engine stopped and i tried to spin it and it only went half a rotation and could feel the air blowing....the clutch seems good.

so why would idle temps go up and then fall when moving if the fan is good? maybe thermostat not opening fully and not enough rpm to pump the coolant fast enough at low speed?

idk but its just running hotter, not hot enough to cause issues yet but its out of the ordinary.

its a hotter time of year but in the mornings and night when temps are low it still behaves same

[jeffnhiscars]

The fan clutch does have a bimetal strip which means it operates independent of coolant temp. When you idle the ambient temp increases due to lack of moving air and engages the fan to prevent overheating, but the engine temp WILL climb. The cooling effect of moving air far exceeds that of the clutch so once you take off the fan will quickly disengage, to be replaced by more effective moving air thus lowering your engine temp.

[digger]

yeah i get that, but its behaving different to normal and i dont want there to be an underlying problem that leaves me stranded if it overheats

[LJ851]

The fan is engaged by hot air passing over it from the radiator. If you have a thermostat that is failing and not allowing enough coolant to pass through and heat the radiator, the fan won't turn on even though the engine is hot.

This happened to me recently. Put a new OEM thermostat in there and see what happens.

[jeffnhiscars]

The fan is engaged by hot air passing over it from the radiator. If you have a thermostat that is failing and not allowing enough coolant to pass through and heat the radiator, the fan won't turn on even though the engine is hot.

This happened to me recently. Put a new OEM thermostat in there and see what happens.

I'm thinking that stat is going to cause it to run hot regardless of whether it's moving or not or even more likely to overheat the car

[LJ851]

I'm thinking that stat is going to cause it to run hot regardless of whether it's moving or not or even more likely to overheat the car

I would have agreed with you before this happened to me. The temps were slightly erratic but ok at speed, coming to a stop caused them to climb A new thermostat later, it works perfect again. Fan was completely inop with the bad 'stat, worked perfect with the new 'stat.

[jeffnhiscars]

The fan is engaged by hot air passing over it from the radiator. If you have a thermostat that is failing and not allowing enough coolant to pass through and heat the radiator, the fan won't turn on even though the engine is hot.

This happened to me recently. Put a new OEM thermostat in there and see what happens.

I think you may have contradicted yourself. If the car is not moving and the clutch isn't engaged, then there is no air moving through the engine compartment to warm the bimetal strip. This suggests that its ambient air that controls which kinda takes the tstat out of the equation doesn't it ? :)

[LJ851]

I think you may have contradicted yourself. If the car is not moving and the clutch isn't engaged, then there is no air moving through the engine compartment to warm the bimetal strip. This suggests that its ambient air that controls which kinda takes the tstat out of the equation doesn't it ? :)

The fan always spins, pulling radiator air over itself. This is why people test the clutch by sticking a rolled up newspaper into the fan, because it's spinning regardless of wether it is engaged or not.

[jeffnhiscars]

The fan always spins, pulling radiator air over itself. This is why people test the clutch by sticking a rolled up newspaper into the fan, because it's spinning regardless of wether it is engaged or not.

This is true...but do we really know if it moves enough air to matter when it's not "engaged" ?

One of the reasons we all love these cars is the voodoo :)

[Ether-D]

It moves a good bit of air even when not engaged. But that's all I can add to this.