300tdi fan continusly spinning

i have done a search but im not getting any answers that makes sence

hopefully someone on here knows the answer to my problem.....

just been watching my engine (checking for leaks) and realised my fan is always spinning ? is this the norm or is there something wrong that i should be looking into ?

thanks in advance....

yes viscous fan allways turn but as they warm up they tighten up and deliver more torque through blades and hence more air fully locked they can sound like a mini jet

jamesmartin is correct - there is a rod coming from the front of the engine into the centre of the fan. As it heats up it expands and grips the fan more, which then causes it to spin faster.

DO NOT TRY THIS, but when the engine is cold, you might even be able to stop the fan spinning with your bare hands! I've never tried it myself, but I suspect it's gripping the fan so loosely, that it wouldn't take a lot to stop it.

You can check it with the carrot test.

I tried that once the bare hands trick, won't be doing that again. It bloody hurts

I took mine off last march not used one since
even fitted an electric one for emergencies not used that either

alex8882 said:

I tried that once the bare hands trick, won't be doing that again. It bloody hurts

Click to expand...

Or... hold a fan blade between gloved (rigger) fingertips while someone else starts the car from cold. If you can't keep hold of the blade then the viscous unit is goosed.

Putting your hand into a moving fan, gloves or no, is a fools game

fishsponge said:

........... there is a rod coming from the front of the engine into the centre of the fan. As it heats up it expands and grips the fan more, which then causes it to spin faster.

Click to expand...

Hi FS, not quite correct actually.

The way a viscous coupling works is that there are chambers within the coupling filled with a liquid. As the airstream coming off the back of the radiator heats up it affects a bi-metallic strip on the front of the VC, which in turn heats the liquid and turns it almost solid, to lock-up the coupling. This then gives full torque to the fan.

thebiglad said:

Hi FS, not quite correct actually.

The way a viscous coupling works is that there are chambers within the coupling filled with a liquid. As the airstream coming off the back of the radiator heats up it affects a bi-metallic strip on the front of the VC, which in turn heats the liquid and turns it almost solid, to lock-up the coupling. This then gives full torque to the fan.

Click to expand...

ooooooo...... i was lied to! (when i was told about it expanding etc...).

thanks for enlightening me!

thanks for the advise guys.... whats the carrot test ? is this just putting a carrot in the fan when its turning ? (this could keep amused for hours)....

yep - you got it!

thebiglad said:

Hi FS, not quite correct actually.

The way a viscous coupling works is that there are chambers within the coupling filled with a liquid. As the airstream coming off the back of the radiator heats up it affects a bi-metallic strip on the front of the VC, which in turn heats the liquid and turns it almost solid, to lock-up the coupling. This then gives full torque to the fan.

Click to expand...

Nearly, but not quite.

A thermal clutch fan operates using silicone fluid as a viscous coupling medium. When the clutch is cool and disengaged, most of the silicone fluid is stored in a reservoir allowing your fan clutch to slip relative to your water pump shaft thereby spinning at a lower RPM than the water pump. This saves you money because the horsepower from your engine is not wasted driving a clutch fan when it's not needed. As your engine heats up, the thermal spring on the front of the clutch expands, which opens a valve allowing the silicone fluid to flow into the spaces between the clutch plates, and drive your fan at an increased RPM approaching the speed of the pulley eventually.



The silicone fluid flows back the the reservoir and stays there if the spring cools down and closes the valve.



It's all very clever, but the one from My TD5 Disco is in the back of the car, and has been for several years.



CharlesY

CharlesY said:

thebiglad said:

Hi FS, not quite correct actually.

The way a viscous coupling works is that there are chambers within the coupling filled with a liquid. As the airstream coming off the back of the radiator heats up it affects a bi-metallic strip on the front of the VC, which in turn heats the liquid and turns it almost solid, to lock-up the coupling. This then gives full torque to the fan.

Click to expand...

Nearly, but not quite.

A thermal clutch fan operates using silicone fluid as a viscous coupling medium. When the clutch is cool and disengaged, most of the silicone fluid is stored in a reservoir allowing your fan clutch to slip relative to your water pump shaft thereby spinning at a lower RPM than the water pump. This saves you money because the horsepower from your engine is not wasted driving a clutch fan when it's not needed. As your engine heats up, the thermal spring on the front of the clutch expands, which opens a valve allowing the silicone fluid to flow into the spaces between the clutch plates, and drive your fan at an increased RPM approaching the speed of the pulley eventually.

The silicone fluid flows back the the reservoir and stays there if the spring cools down and closes the valve.

Click to expand...

even closer, but still not quite right i'm afraid.

as you turn the key to start the engine, it engages the witchcraft mechanism. This monitors the engine temperature, wind speed, ambient air temperature, fuel temperature, exhaust temperature, turbo & intercooler temperature and various other metrics by pure magic. If any of them becomes hotter or colder than a pair of frogs legs, it engages the fan using telekinesis.

sorry to interupt....

Can i get rid of the fan and fit an electric one?

Cheeksgt said:

sorry to interupt....

Can i get rid of the fan and fit an electric one?

Click to expand...

yes

Cheeksgt said:

sorry to interupt....

Can i get rid of the fan and fit an electric one?

Click to expand...

you asked the question i had on my mind..... is the electric fan better ? also is it an easy fix ?

ugly duck said:

you asked the question i had on my mind..... is the electric fan better ? also is it an easy fix ?

Click to expand...

yes and yes

The leccy fan is best (and easiest) fixed with a ON/OFF switch, and don't bother with the thermostatic switch.

You would turn the fan on on hot days, when you are going slowly, BEFORE you start up steep hills, and whenever you stop in traffic.

In my TD5 Disco, the whole fan is taken off about October, and it stays off the car till the next summer. The car is a good deal quieter without it.

CharlesY

CharlesY said:

The leccy fan is best (and easiest) fixed with a ON/OFF switch, and don't bother with the thermostatic switch.

You would turn the fan on on hot days, when you are going slowly, BEFORE you start up steep hills, and whenever you stop in traffic.

In my TD5 Disco, the whole fan is taken off about October, and it stays off the car till the next summer. The car is a good deal quieter without it.

CharlesY

Click to expand...

so in other words the electric fan is only used when the engine is too hot ? is it wired to a switch in the cab area ?

ugly duck said:

so in other words the electric fan is only used when the engine is too hot ? is it wired to a switch in the cab area ?

Click to expand...

Not quite.

The THERMOSTAT tries to keep the engine at the correct temperature by allowing SOME very hot coolant into the radiator.
The coolant comes back out the radiator too cold, but is then mixed with hot water from the by-pass passages at the water-pump, and goes back to the block at just the right temperature to let the engine run nice and cosy.

If the system starts to heat up, the thermostat opens wider and wider, sending more coolant to the radiator, and it SHOULD keep things under control.

If you are driving very slowly (or stopped in a jam on a hot day) and you have no fan runing, the engine will heat up and boil the coolant.

This is when you turn on your leccy fan, though you being a smart-arse will anticipate the situation and turn the fan on long BEFORE the heating up starts, thus leaving a nice cool gallon of coolant in the radiator, AND sending a lot of cool-ish air into the engine bay to help stop that whole area getting too hot.

Electric fan is a great idea because YOU can control it.

CharlesY