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Viscous Fan


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Hi,

I did do a search, can find lots of thread about their removal, but not a lot about fixing them.

My viscous fan isn't working, it's not kicking in - after a run up the motorway, when left at idle the engine temperature will increase into the black section of the gauge (I know they're not accurate, but they must give a representation of what's going on) without the fan doing anything than slowely go round.

This is fairly new, it's only been a problem for the last week or so.

Is it possible that there could be something loose inside?

I just saw the price of a new viscous coupling on Rimmer Bros, and don't fancy paying it!

Cheers.

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I have a complete viscous fan assembly for a 200/300tdi for sale.

It's never been used so in as new condition.

£65 + post, but you are not far away from me.

I am at the eastern end of the A505 where it merges with the A11.

PM me if interested.

John

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I remember this topic came about in the former LR Enthusiast forum, and someone said that it was possible to top up the silicone fluid (low level being the cause of malfnctioning, most of times); the down side being that this special silicone fluid was to be bought at Toy***ta dealers!

Hope I won't get banned right at the begininng for using such a bad word...

Can't say if Marmite is up to the job...

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look on ebay I have purchased a few 300tdi ones on there (new) and paid £30ish

Ebay - good thinking. There are a few on there that I will keep my eye on.

I've just brought the car to work, the car definatley gets hotter when it's stationary - which I guess points to the fan.

Top hose is hot (but not so hot you can't hold onto it) bottom hose is cooler.

I gave the viscous coupling a decent look this morning. It doesn't appear to have leaked, there is no sign of the fluid leaking out. Also, my second post on this thread wasn't correct. The fan doesn't spin freely, it still feels like it's guts are still in place.

It isn't, however kicking in. Even sat idling after a 60 mph run on the motorway.

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In your first post you say "... it's only been a problem for the last week or so.".

What exactly makes you think there is a problem? That it isn't 'kicking in'?

Why do you think it should 'kick in' in the current UK weather conditions?

None of the circumstances you have described, continual idling, idling after a 60 mph run, etc, make me think the VC would have 'kicked in', in the current UK temperatures.

I have run a VC equipped Diesel LR for the last 9 years, experienced fan VC failure once, and have answered numerous queries about them on different LR Forums.

"after a run up the motorway, when left at idle the engine temperature will increase into the black section of the gauge"

Give me more information about your gauge please.

What colour is Cold; White?

Where is the centre position, needle straight up, or straight down, or horizontal?

The central area is what colour; Black?

High temperature is Red?

When you are doing 60mph down the motorway, is the needle at the central position? A needle width 'cooler'?

If you want to know what a 'kicked in' or 'locked' fan VC sounds and feels like, turn the fan by hand after the car has been standing unused and outside overnight. Even better if there is an overnight frost. The resistance you feel is close to the resistance when very hot.

Now start the engine, immediately speed it to 2000 ish rpm. The wind noise you hear, and the air movement you feel, (by holding a hand above the space between radiator and engine) is what happens when the VC is very hot and the VC has 'kicked in' or 'locked'.

Now let the engine tickover and listen to the wind noise from the fan. After 2 / 3 minutes the wind noise and air movement will drop.

Stop the engine and spin the fan, the resistance should be markedly less than than your first test, and is what you should feel in any condition from after just 5 minutes running, up to normal temperature.

Now, in what way is your fan not complying with the description I've just given?

HTH

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Now, in what way is your fan not complying with the description I've just given?

HTH

Hi David, that's quite a reply, thank you for your time.

Until a week ago, the temperature needle would slowely rise to vertical (so, half way round the gauge) and stop. No matter what the car was doing, crawling down lanes or being driven on the motorway, it would never go above this.

Now, for the last week or so, the needle has been rising as expected, but goes well past vertical, and sits at least 2/3rds of the way round the gauge when being driven, unless the car is idling, say in very slow moving traffic, the needle will will move all the way through the white, into the black bit just before it goes red.

(The first two thirds of the gauge are white, then there is a thin black bit, then the final quarter is red).

The viscous fan, which I would expect to come on (kick in, lock up) by the time the needle has swung into the black section never does. In fact, if left to idle for long enough, the gauge hits the red, and still the fan idles round moving very little air.

I've read that if the fluid leaks out of the viscous coupling, then the fan will feel loose, and spin easily on it's bearings. Mine does not, with the engine off mine still feels tight - there is significant resistance when it is turned.

The belts are in good condition and are the right tension.

I changed the coolant and thermostat last weekend, but it made no difference.

The coolant was clean, there is no evidence of any oil contamination. The car is not smokey and the engine oil is clean, and shows no signs of "mayo".

I will try and get hold of a decent temperature gauge, so that I can see exactly what is going on, but at the moment i've no reason to not believe the one mounted in the dash.

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Until a week ago, the temperature needle would slowely rise to vertical (so, half way round the gauge) and stop. No matter what the car was doing, crawling down lanes or being driven on the motorway, it would never go above this.

OK, that's what I'd expect.

Now, for the last week or so, the needle has been rising as expected, but goes well past vertical, and sits at least 2/3rds of the way round the gauge when being driven, unless the car is idling, say in very slow moving traffic, the needle will will move all the way through the white, into the black bit just before it goes red.

(The first two thirds of the gauge are white, then there is a thin black bit, then the final quarter is red).

OK, on the assumption that the gauge and sensor is good, I can see why you think there is a problem.

The viscous fan, which I would expect to come on (kick in, lock up) by the time the needle has swung into the black section never does. In fact, if left to idle for long enough, the gauge hits the red, and still the fan idles round moving very little air.

I'd agree with your reasoning, and with the needle in the thin black I'd expect a blip on the throttle (to about 2500 / 3000 rpm) to create a noticeable roar from the fan, so loud you would hear it from the driving seat, with the bonnet closed.

I've read that if the fluid leaks out of the viscous coupling, then the fan will feel loose, and spin easily on it's bearings.
Yes, I'd go with that.
Mine does not, with the engine off mine still feels tight - there is significant resistance when it is turned.

This result does depend so much when you test it.

With a overnight stand the fluid collects in the bottom of the VC, and locks the inner and outer together. This gives a strong resistance.

The initial 5 minutes running, even just at tickover, centrifuges the oil to it's correct position, creating a weak bond between inner and outer, making the blades easy to turn manually, allowing a lot of slippage when the engine is running.

When the very hot air from the radiator hits the VC, a thermally operated valve opens, and the oil flows to make a strong bond between the inner and outer, forcing the blades (connected to the outer) to move at the fast speed of the inner, thus moving more air.

Unfortunately, a lot of this is relative, until you have gained the experience of what feels good, and what feels bad, it is difficult to be certain what you have.

The belts are in good condition and are the right tension.

I changed the coolant and thermostat last weekend, but it made no difference.

The coolant was clean, there is no evidence of any oil contamination. The car is not smokey and the engine oil is clean, and shows no signs of "mayo".

OK, have you rechecked for an airlock - ie, does the heater produce a good strong output, or at least, do both pipes get hot?

Does turning the heater fan on high pull the engine temperature down when it's near or in the black?

I will try and get hold of a decent temperature gauge, so that I can see exactly what is going on, but at the moment i've no reason to not believe the one mounted in the dash.

When the gauge is in the black, or the red, does the engine smell hot? With the gauge that far over the heat should be radiating strongly from the block and hit you in the face when you open the bonnet.

You mentioned Rimmers, while a good reputation for service is reported on forums, particularly for overseas customers, they aren't the cheapest place. Get a Paddocks price, it will probably be a Britpart unit, but I've run one for years with no regrets. Unfortunately I don't know your area, so can't comment on any local suppliers. Now you have found Rimmers you will have a part number.

Also look for a new sensor.

Presumably there has been no other recent changes or problems that are apparently unconnected?

I'm not jumping one way or the other just yet about the VC. If it is that I'll expect you to say the engine smells hot, and that drawing heat out via the heater (windows open to let it escape), keeps the temperature under control.

VCs generally fail by slowly leaking oil (look for a very dirty front face, and oily dirt on your fingers after touching the blades), or they seize almost solid, in which case they make lots of wind roar. Sometimes the bearings go, but you would have felt the blades wobble if that was the case.

Good Luck.

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Now, for the last week or so, the needle has been rising as expected, but goes well past vertical, and sits at least 2/3rds of the way round the gauge when being driven, unless the car is idling, say in very slow moving traffic, the needle will will move all the way through the white, into the black bit just before it goes red.

I don't have a VC fitted. I've a thermostatically controlled electric fan, which never comes on unless the truck is working very hard at low speed.

Motorway, lanes, traffic around town, all have the temp gauge sitting at vertical (normal), so I'd suspect that while your VC may or may not be working, the root of the problem is something in the cooling system itself; dead thermostat, airlock, or blocked radiator.

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Thanks for the replies all - I really appreciate it, especially as a relative newbie on the forum.

The engine does not smell hot. Putting the heaters on did not make a significant change to the engine temp (in other cars i've had, when doing this, the gauge has reacted very quickly), but the heater does blow hot air.

When the engine is hot, a blip of the throttle does not cause the fan to speed up.

I have not ruled out a duff gauge. I only thought of it now, but the alternator light is taking longer and longer to go out (i.e. it doesn't go out when the car is started and is idling, it only goes out after you have pulled away and the revs have risen a bit). I'll have a look at the earth strap from car to battery - perhaps it's got grubby and is causing the gauge to malfunction?

So, I have an action plan for this weekend.

Start the car with the bonnet open, see if the fan initially roars into life, before slowing down.

Take the car on a quick run, but not up to temperature. At this point the silicon fluid should have been distributed round the fan and it should not be locked - i.e. easy to spin by hand.

Get the car hot, turn it off, see if the fan is now "locked".

I guess this should prove the condition of the viscous coupling?

I'll also find a clean bucket to drop my coolant into (which I only replaced last week) and flush the radiator and try and bleed it properly.

Can anyone point me in the direction of a comprehensive "how to" to the correct procedure?

Thanks again. :)

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See post number 6 here for a simple guide to what goes on in a viscous fan coupling.

Chris

Thanks, that's made things much clearer.

I have already cleaned out my rad by removing the grill and spraying it with a hose, but have not taken off the cowling and done it from behind. Before doing anything I will try this - see if the radiator is so blocked that no hot air is passing through to the fan (and thus, it is not activating the viscous coupling).

Good job I didn't have anything else planned for tomorrow!

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The engine does not smell hot. Putting the heaters on did not make a significant change to the engine temp (in other cars i've had, when doing this, the gauge has reacted very quickly), but the heater does blow hot air.

When the engine is hot, a blip of the throttle does not cause the fan to speed up.

To me, sitting securely and comfortably facing my PC, these results tell me the engine is not overheating

I have not ruled out a duff gauge. I only thought of it now, but the alternator light is taking longer and longer to go out (i.e. it doesn't go out when the car is started and is idling, it only goes out after you have pulled away and the revs have risen a bit).

On a 38A, a bad engine to chassis earth connection is often revealed by the temperature gauge malfunctioning. I hestitate to carry the cause / result comparison too far, and the visible effects of high resistance earths can be difficult to define on paper, but....

Note that all car electrical systems have two earths, the alternator case, and the battery Negative terminal. If these are electrically tied together everything is fine. If the link is high resistance, then the gauge sender will be sending the alternator earth, via the high resistance path to the gauge, which is completing the circuit to the battery earth, thus you see that the different earth potentials cause problems.

I'll have a look at the earth strap from car to battery - perhaps it's got grubby and is causing the gauge to malfunction?

Note there are two earth cables to check, engine to chassis, chassis to battery. Yours may be Engine to Battery, Battery to Chassis, but they both need checking.

So, I have an action plan for this weekend.

Start the car with the bonnet open, see if the fan initially roars into life, before slowing down.

Take the car on a quick run, but not up to temperature. At this point the silicon fluid should have been distributed round the fan and it should not be locked - i.e. easy to spin by hand.

Get the car hot, turn it off, see if the fan is now "locked".

I guess this should prove the condition of the viscous coupling?

"Get the car hot" in this case means very close to or into the black, although as I said earlier, I don't think the engine is overheating, so even if you get the gauge into the Red, the engine won't be hot enough to tighten up the VC.

Gauge sensor or poor engine earth, or possibly faulty alternator, are my current favourites.

If you have a digital voltmeter, with the engine running, measure the DC voltage between the alternator case and the battery negative terminal. Put a heavy electrical load on, headlights, + any heated screens, + heater fan on high. You are looking for fractions of a volt on a good system. One volt would be a bad system.

Then just for kicks, set the voltmeter to AC, and measure across the alternator, +ve to case. This should be nothing, but it sometimes finds a faulty alternator, otherwise it proves it 'clean'.

Hope it doesn't rain too much, I'm green lane navigating and gate opening on Saturday pm :-)

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Don't worry about the fan - I haven't had a working one fitted for the last two years and the only times I've got to the stage of overheating has been when I reached the top of the Alps in the summer, and hoofing up sand dunes in the sahara.

It's not warm enough here yet for it to make an impact unless you're doing heavy towing etc - the rad is good enough to cope on its own.

Do the usual checks - is the thermostat opening and letting coolant circulate through the rad? is the rad blocked inside with gunk or outside with mud in the vanes? Airlock?

Also check the wire coming off the temp sensor in the thermostat housing - I've seen the same symptoms you describe being caused by a slightly chaffed wire earthing out on the engine block.

You can check if the viscous coupling is knackered by getting the engine hot then poking a rolled up newspaper in it. If it turns to hamster bedding, the fan works, if the fan stops, change it!

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On the viscious unit there should be a tiny coil spring, heat sensitive, which controls the opening and closure of the inner valve: might be worth checking if this spring is clean and free to sense heat and move, opening the valve. If it is clogged with dirt, it might not work properly.

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So many great replies! Thanks loads all!

(This is THE best Landrover forum i've found!)

Looks like i've got loads to check tomorrow - will report back after a day's fault finding.

Thanks again.

:)

On the viscious unit there should be a tiny coil spring, heat sensitive, which controls the opening and closure of the inner valve: might be worth checking if this spring is clean and free to sense heat and move, opening the valve. If it is clogged with dirt, it might not work properly.

Where abouts on the unit is this spring? I thought the VC unit was pretty much sealed up?

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So many great replies! Thanks loads all!

(This is THE best Landrover forum i've found!)

Looks like i've got loads to check tomorrow - will report back after a day's fault finding.

Thanks again.

:)

Where abouts on the unit is this spring? I thought the VC unit was pretty much sealed up?

Right in the centre of front face of the VC unit - the side nearest the rad

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Temperature...

Last Sunday we had a day out.

The ambianent temperature didn't rise above 4deg C

The engine coolant temperature didn't rise above 80deg C It mostly stayed at 76deg C

The normal engne coolant temperature on my truck is 86deg C That is normal between 20deg C and 35deg C ambiant. Honestly I don't think it's been warm enough for the viscous fan to think about working.

By ten bobs worth

mike

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