Clutch Fan 101

[rion]

I have 2 salespeeps and 2 mechanics tell me that a thermo clutch fan should be fully engaged on cold to warm, while slippy on hot. and the amount silicon oil should be full... they say silicon oil will become slippy when it is hot enough...

contrary from what I learned from the net. that thermo clutch fan should be parialy engaged on cold-warm and becomes fully engaged only when reaching a particular hot temperature.

then if the silicon oil is full, it will make the fan always fully engaged. and I think silicon oil does NOT become slippy when hot, but it's the mechanical thermostat thingy that pulls the silicon oil on the inner part making it engaged when hot enough...

need your input guys, which is true? and how much silicon oil do I really need?

[mbeige]

It's called a clutch system because it technically engages and disengages the main engine cooling fan. That's where the clutch term comes in. Viscous because the engagement is done by the silicone gel inside the clutch that uses friction to engage the fan.

Basically there's a metal blade in front of the clutch. If it gets hot, it expands, right? When it expands, the metal tab bends a little, letting the small pin out from its hole. This pin is like a gatekeeper that allows the viscous fluid to flow and "engage" or "bite" allowing the fan to cool the engine when it gets hot as in the first condition.

So as you drive faster that cools the metal strip in front of the clutch assembly, which makes it straighten up from being bent, so it pushes the pin back inside and the silicone gel goes back to where it came from, disengaging the clutch at high speed because it's not necessary for cooling the engine (primarily because the airflow is significant enough to do that job).

My best guess is you'll need to test it out yourself, some clutches have different capacities than others.

When the engine is cold, the fan should not engage. This allows the fan to "slip" and not bite the clutch, allowing the engine to warm up faster. When it gets up to temp, it engages to cool the engine, when it gets cool once more, as in high speed drives, like I mentioned above, it will release the clutch once more and allow the air flow to cool the engine instead.

When in traffic, that's where the auxiliary fans come in. Most cars today have two, one for when the AC is in use and another to cool it down when it reaches a certain high temperature. Or perhaps it's slightly different for other makes.

[rion]

When the engine is cold, the fan should not engage

that's what I needed to hear. I was confused when 4 people tell me the wrong way. arghh... the poor customers with their noisy fan with lesser power.

as for the amount of silicon, indeed, I have to test it out. good thing I can access other same engine models and compare the bites.

thanks mbeige.

[mbeige]

No problem, glad to be of help

[alwayz_yummy]

pag add lang like ginawa sa liteace ko noon,mga 2-3 vials. dapat at room temp maiikot mo yan.

pag nasa running temp ung engine pag pinigil mo ng thick slipper, di mo mapipigil.

one of the misunderstood parts of the car, na ang ginagawa ng tamad/ nagmamagling na mekaniko--binubutasan/winewelding.. bad yun!

[mbeige]

How much is one vial? 2-3 vials is still vague depending on the volume of each vial. Hope that clears things up.

[alwayz_yummy]

standard lang ang size ng isang vial--for a toyota/denso silicone oil ung red box, as i recall 120/vial.

2 lang nagamit sa dati kong ace.. to test kung kailangan- at engine running temp., use a thick slipper to stop the clutch fan, pag nahinto mo, dagdag ng oil, nasa cardoimain ng liteace ko some procedures when it was done.

[mbeige]

I see, just make sure alam mo kung ano direction umiikot makina

[rion]

thanks. based on my research, it should only engage when it reaches 80°c.

and Thermal fan clutch is briefly engaged at cold start-up. and I can confirm this pretty much.