Average engine temps

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Originally Posted by josh.huber

The fan control is important for the ECM because they such massive amounts of power from the engine. So are only driven when required.

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Interesting, as I I’ve been diving into understanding this component to decide if I should replace it.

The thermostatic fan is an amazing bit of engineering. The special oil can leak out and there is videos of rebuilding and replacing the oil.

The oil emerges from is central reservoir via a thermostat valve and is driven by centrifugal force to fill the outer capillaries and bind the fan into turning with the engine (bit like an auto gearbox TC). When the temp drops it gets trapped back in the centre reservoir and the fan freewheels.

Now, what I don’t know is if the traditional non electronic thermostat (bimetallic strip or similar) is fully replaced or augmented electronically in the Disco?

What I do know is that the ‘rule of thumb’ test of listening for the roar on cold startup is common to all thermostatic fans as the oil leaks out at rest until on startup it is forced (spun) back into its reservoir on startup until it freewheels until it’s needed.

It is not signifying IMHO that the ECU is doing a test on it. It does indicate the oil is present and circulating normally.

I’d be keen to understand how the electronic aspect interacts and if it just overrides the thermostat or replaces it?

It does not seem also to have the ability to operate partially. Once the oil is out it’s either locked or freewheeling.

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Originally Posted by shanegtr

Just remember that the grade of oil is specified at 100 degC(for engine oil). Typically once you start exceeding that temp the oil viscosity is going to continue to decrease. Not all oils will respond in the same way to increased temperature and the ability to resist changes to viscosity is known as the viscosity index. Typically synthetics have a higher viscosity index's than mineral, and can handle higher temps for longer before oxidising. But just keep in mind that most oils that are marketed as a synthetic are not really a true synthetic as you may think, they are most likely a class 3 base stock which is just a highly refined mineral oil. Mobil 1 is the only full POA synthetic that I've come across so far.

Back onto the engine coolant temps, my engine fan will really kick in around 117deg from memory - at least thats the point where you can hear it working

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Yeah oils ain't oils, how do the mineral oils perform as far as lubricity at higher temps? Besides losing viscosity I thought it was the main risk. As they may maintain enough viscosity for pressure but will not be able to reduce friction in moving parts.

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Originally Posted by PerthDisco

Interesting, as I I’ve been diving into understanding this component to decide if I should replace it.

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The old test used to be shove a rolled up newspaper at the fan. If the fan stopped the clutch was done, if you ended up with confetti it was fine.

I've not looked into the mechanical aspect of how it works, but the ECU modulates the control valve to give proportional control of the fan. I've sat at constant RPM and watched the fan RPM vary with the varying control duty cycle.

I always thought the roar on startup was the cold thick oil and as it warmed up the fan dropped into a controllable state. That's how it works on my other car with the thermo-viscous coupling.

https://uploads.tapatalk-cdn.com/202...2900a236e5.jpg

They are awesome things.

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Originally Posted by josh.huber

https://uploads.tapatalk-cdn.com/202...2900a236e5.jpg

They are awesome things.

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Would be interesting to know how it does that amazing variability because the oil is either in or out on a standard unit. If the electronic could pulse the oil release it could restrict the oil volume and create some slip between 0-100%. I’d love to know.

I don,t really know, but once I was doing some work on the cooling system and I disconnected the cable to the fan. When I completed the work and reconnected the fan it did not cut in when the engine first started. At the time I did not have a code reader so it was a few days before I could get my Indi to check the problem. For those few days the fan never once cut in at start up. When the Indi checked there was a fault code showing which he cleared and then the fan started working again as normal. This would indicate to me that the fan needs the electronics to vary the speed that it runs at including the start up check so therefore it is not the oil inside settling outside the central reservoir causing the fan to operate at start up.

Cheers,
Murray

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Originally Posted by murray073

I don,t really know, but once I was doing some work on the cooling system and I disconnected the cable to the fan. When I completed the work and reconnected the fan it did not cut in when the engine first started. At the time I did not have a code reader so it was a few days before I could get my Indi to check the problem. For those few days the fan never once cut in at start up. When the Indi checked there was a fault code showing which he cleared and then the fan started working again as normal. This would indicate to me that the fan needs the electronics to vary the speed that it runs at including the start up check so therefore it is not the oil inside settling outside the central reservoir causing the fan to operate at start up.

Cheers,
Murray

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Typically it’s close interference between the two halves (fan half and input half) like two coarse hair combs fitted together but not touching. The oil when present causes the grip without any mechanical connection. Its on or off.

To get variability is more like a wet clutch on a motorbike or the Transfer Case with all associated oil fouling, filtering and servicing needs.

So, I’m sceptical it’s anything more than an electronic over ride feature.

Only theorizing hear but maybe it's like active type shock absorbers that you can adjust the dampening while driving. I believe they change it electro magnetically. Don't really know how they work but I believe they is some sort of magnetic material suspended in the oil of the shocks that when you pass a current through it, it changes the viscosity anywhere from very fluid to locked up solid. This type of system would work for the fan.

https://www.haydenauto.com/media/567...ts_6980012.pdf

Pretty good read on how they work and vary the speed

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Originally Posted by Milton477

100 to 108 deg towing 2.8 tons at 35deg. Fan only kicks in over 100. If you have a GAP tool, you can watch the Viscous Fan Setpoint rise & fall as the cooling water temperature fluctuates.

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Ditto!

95 - 105 C towing a 2,500 kg boat at 100 kph in 35 C outside temp - by the GAP tool 'live'!

Gets up to 115 C on a long pull up the Toowoomba range!

Transmission temp is generally about 5 degrees less.