viscous fan

hi . i have a 51 plate td5 auto with 112000 on the clock. how do i check if the viscous fan is working as it should. many thanks

Can't find a definitive testing technique, but I should think that the fan should "freewheel" when it's cold and when the engine and cooling system is up to temperature it should be stiff to turn by hand.

As to what temperature it should all get to the point where it's being driven by the engine, I've no idea.

Does it sound like a 'turbine' when starting from cold for the first 50 yards or so down the road, that's before the fluid circulates into the chambers and the viscous coupling frees up.

If so its working.

U may or may not have the same sound when on a hot day with a/c on and in traffic the viscous locks up fully which mine does.

take a big carrot or a bigger piece of foam which you can bin after the test, start the engine from cold, you have to gently approach the fan's blades with the carrot or foam and apply decent pressure(watch your hands) ... when the engine is cold the fan must stop, when it's up to working temp it must rip pieces from the carrot/foam... if it doesnt stop when cold it means it's stuck and it will cool even when it's not necessary prolonging the engine's warming up, if it stops with warm engine it means it doesnt lock and you can end up with overheated engine...simple as that

Some FAQs on viscous fan couplings Fan Clutches

I threw mine away about 4 years ago when it seized - waste of space in my opinion.

alan morgan said:

hi . i have a 51 plate td5 auto with 112000 on the clock. how do i check if the viscous fan is working as it should. many thanks

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Take it off and keep it in your boot with a spanner.

sierrafery said:

take a big carrot or a bigger piece of foam which you can bin after the test, start the engine from cold, you have to gently approach the fan's blades with the carrot or foam and apply decent pressure(watch your hands) ... when the engine is cold the fan must stop

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Exactly, except I actually used my finger. When cold you can even spin it backwards by hand. DISCLAIMER! I am in no way responsible for other people losing parts of their anatomy - viscous fan couplings may vary

If u can "spin" a viscous fan when cold there's a problem with the coupling.

discool said:

If u can "spin" a viscous fan when cold there's a problem with the coupling.

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+1 - the fan will be stiff on a cold, un-started engine. Then it starts to free off when the engine is started and warming up. Finally, if the heat given off the radiator is high enough the fan clutch will start to lock-up giving full cooling.

Dave

I take mine off in the winter, as it only serves to slow down warm up.......

m500dpp said:

I take mine off in the winter, as it only serves to slow down warm up.......

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just dont do any towing or off-roading then cos you'll "tenderise" the head... the gauge leaves teh middl at around 120*C and a non properly cooled Td5 would often work at 110*C or more without even knowing it... especially if the electric cooling fan misses or doesnt work...and on a long run that's not healthy for the engine believe me

Fair point. Our Disco only goes short distances on road, we do tow a horse box occassionally, but only about 10 miles each way.

I have noticed that the temp gauge doesnt move, in the summer towing back from East Grinstead there is a long 3rd gear slog, and the engine smells warm (with viscous fan on) but the gauge doesnt move...........