TD5 Viscous Fan problem

How should the fan feel when you turn it by hand with the engine off???

today while driving at higher revs I was getting a stange sound and squeeling and suspect it is the fan unit.

turning it by hand it dosent feel smooth at all, a bit wobly and sticky and gritty.. this cant be right???

heading on an epic voyage next week though france to spain so your input would be great...

should I replace it, it is still doing it's job but the viscous connection seems shot...!

There is a bearing behind the fan - it is most likely that. It's a bit of a menace to change though. At least LR actually sell the bearing (although we don't buy from them) unlike the 300tdi where you have to change the timing case.

Thanks Jim,

Feels very much like it could be a broken bearing in the hub of the fan. Had a look at the parts catalogue couldnt see a bearing listed though.

battenberg said:

How should the fan feel when you turn it by hand with the engine off???

today while driving at higher revs I was getting a stange sound and squeeling and suspect it is the fan unit.

turning it by hand it dosent feel smooth at all, a bit wobly and sticky and gritty.. this cant be right???

heading on an epic voyage next week though france to spain so your input would be great...

should I replace it, it is still doing it's job but the viscous connection seems shot...!

Click to expand...

It should have no resistance when cold and sort of spin freely and then when up to operating temperature, stop engine and you should feel a lot more resistance! un that!

Bearing, roller, viscous fan to cover. ERR5285 .

Jason2 said:

It should have no resistance when cold and sort of spin freely and then when up to operating temperature, stop engine and you should feel a lot more resistance! un that!

Click to expand...

Got myself a new fan and put it on... however the new one (brand New OEM LR part) does not freely spin at cold.. it this right?

battenberg said:

Got myself a new fan and put it on... however the new one (brand New OEM LR part) does not freely spin at cold.. it this right?

Click to expand...

Sorry mate bit misleading that! More like it should turn freely when cold and when hot (like realy hot) there should be a lot more resistance as the liquid in them thickens under heat increasing the drive.

It may just be my misconception of the idea of a viscous fan. I was assuming that the viscous unit would allow the engine to rev freely with the fan sort of catching up... then when cruising eg motorway the fan would catch up and stay up to speed increasing in its ability to bind to the shaft according to temperature.

i also thought that with the engine off I should be able to spin the fan by hand where it should rotate faily freely... this dosent seem to be the case..

Heading into France tomorrow and journey down into Spain, where abouts are you in the grand picture?

battenberg said:

It may just be my misconception of the idea of a viscous fan. I was assuming that the viscous unit would allow the engine to rev freely with the fan sort of catching up... then when cruising eg motorway the fan would catch up and stay up to speed increasing in its ability to bind to the shaft according to temperature.

i also thought that with the engine off I should be able to spin the fan by hand where it should rotate faily freely... this dosent seem to be the case..

Heading into France tomorrow and journey down into Spain, where abouts are you in the grand picture?

Click to expand...

Viscous fan drives are used to reduce the fan load when cooling is not required, and thereby lessen power requirements and related fuel demands. A viscous fan drive offers an improvement in efficiency over direct drive fan cooling. This hub-mounted, fluid-coupled device contains a hydraulic turbine using a viscous silicone fluid to transfer energy from driving element to driven element.
Typically, a bi-metallic element on the front of the viscous drive senses the temperature of air passing through the radiator and operates a valve to control the silicone transfer fluid, thus effecting fan engagement and disengagement. The fan drive is not controlled directly by engine temperature but indirectly by sensing the temperature of cooling air passing through the radiator.
The hydraulic nature of a viscous drive prevents it from achieving fully on or fully off operation. Consequently, in the disengaged mode, the fan continues to operate at speeds as high as 45 percent of the fully engaged rate, usually between 650 to 1000 rpm.

We are about 20mins off the A10 between Poitiers & Niort,pop in for a brew if you have time

Where abouts in Spain are you going?

Thanks Jason for the info

playing the whole trip by ear really! crossing dover calais on saturday, then two weeks later getting the bibao ferry back to UK, no particular route but some idea's of what I want to take in... Millau viaduct being one...

The viscous coupling ALWAYS drives the fan at least a little.
Therefore you will always feel a little drag on it even when it is stone cold.

The reason for wanting it to run a little are these:

First, it is HEAT that makes it drive more when the engine heats up, and that heat comes from the radiator, but if the car is parked with the engine running (worst case situation as in traffic) or driving very slowly in low range first gear or reverse, there will be no natural air flow from the hot radiator to the viscous coupling, so the coupling won't find out the engine is too hot, and it won't drive the fan more - so it boils up.

Because the fan always runs a little, it is always pulling air through the radiator, and the coupling damned soon gets hot as the engine heats up the radiator.

Second, running the fan a little stops the air around the exhaust from getting too frigging hot for comfort, and melting all the plastic bits. It provides enough under-bonnet ventilation to make a difference.

This is one reason why electric fans are not always a good idea.

The turning of the coupling should be completely smooth ... no grittiness and nasty noises.

CharlesY

Thanks CharlseY... the new fan is completely smooth.

was just curious as to how 'viscous' the coupling should be as the only other one I'd felt was the broken one...

Yeah,

But first my apologies to Jason2 because I hadn't seen his good reply when I sent mine. I could have saved my keyboard ....

"Vicious coupling" is also an apt name for these things, because even on tickover on a cold day those blades will inflict a sore one if your fingers get involved.

It is tempting to hoick the fan off (one whack with a fan spanner spins it off on a LEFT HAND THREAD!) and it is so easy to do this that I tend to do so on a long run if there's not a lot of risk of stoppages. The worst case would be stop, lift bonnet, spin fan on by hand, smack with fan-spanner, shut bonnet, two-finger the guy behind who was tooting, and drive on.

But when the car is cruising along through the air, the blast of air comes through the radiator at some speed and thus takes the load OFF the fan anyway, and in effect even if the viscous coupling heats right up into lock-up, it won't be doing a lot of WORK to pull the air through as the air is already streaming in anyway. If little or no WORK needs done then little or no fuel is wasted in the process. In this "hot engine" situation the fan really starts to work on the air through the radiator when road speed reduces, and maximises when speed drops towards stationary.

Try taking it off on the motorway.
You may notice a decent noise reduction too.

CharlesY