TD5 Viscous fan unit

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Scooby22

Scooby22

Well-Known Member
Posts
1,247
Location
County Durham
About 6 years ago on my way to work my viscous fan unit unscrewed itself and fell off, there was a bit of a clatter then fell silent before I could pull up, found it wedged to one side, I pulled it out with some battle damage to a couple of fan blades where it had hit the drive belt and shoved it in the back and continued on my way to work, watching the temperature gauge carefully, it never moved from its normal reading.
On my way home again never moved from normal, I looked on ebay to see if I could get replacement fan blade unit but could only find the full viscous fan unit at silly prices, I continued to use my TD5 while looking for the blades or a cheaper unit, and temperature never moved above normal reading no matter how far or hard I drove it, (including long stretches of motorway and stuck in traffic jams).
I changed the thermostat in case it was not closing and keeping the engine cool but it was still the same after changing it, I just stopped looking for a fan and have driven for over 6 years now with no problems at all. I sometimes wonder if not having it may result in less air being sucked through the intercooler at low speeds but have not noticed any drop in power.
Has anybody else removed theirs and had the same outcome, in my case I conclude it is not required on my TD5.
 
Scooby22 said:
About 6 years ago on my way to work my viscous fan unit unscrewed itself and fell off, there was a bit of a clatter then fell silent before I could pull up, found it wedged to one side, I pulled it out with some battle damage to a couple of fan blades where it had hit the drive belt and shoved it in the back and continued on my way to work, watching the temperature gauge carefully, it never moved from its normal reading.
On my way home again never moved from normal, I looked on ebay to see if I could get replacement fan blade unit but could only find the full viscous fan unit at silly prices, I continued to use my TD5 while looking for the blades or a cheaper unit, and temperature never moved above normal reading no matter how far or hard I drove it, (including long stretches of motorway and stuck in traffic jams).
I changed the thermostat in case it was not closing and keeping the engine cool but it was still the same after changing it, I just stopped looking for a fan and have driven for over 6 years now with no problems at all. I sometimes wonder if not having it may result in less air being sucked through the intercooler at low speeds but have not noticed any drop in power.
Has anybody else removed theirs and had the same outcome, in my case I conclude it is not required on my TD5.
Click to expand...
Can't speak for a td5 but loads of guys drive there TDI 200 - 300's without fans in the UK. I drove my 200 here in France in temperatures of 35c without any problems. If you are going to tow stuff you might well need a fan thought or if you are going to do a trip across Morocco.
 
Yes tried mine without it, it runs fine if you are in the UK and not towing anything
But I found myself watching the gauge like a hawk, I read how overheating can wreck the head, and if you think fans are dear look up the price of a head.
The TD5 fan is not like the 200 - 300 ones you will only find the full unit, for sale, the others sell the hub alone.
I bought a Bearmach one couple of years ago and its working fine.
One word of warning I bought second hand off e-bay, and it was another case of people who buy a new part and shamelessly put the duff one on there, I would recommend anyone to bite the bullet and go for a reputable supplier.
 
I dont tow with my TD5 I use my XC90 for that, but like you was watching temp gauge closely, still do, but after 6 years I think it is going to be fine in normal use. I did tow my caravan once with it and it still only went to normal temp but that was only a short trip of 20 miles on a dual carriageway with only slight inclines
 
neilly said:
@raywin

Is the Defender not like the D2, in which the temp gauge only indicates a range of temp when it is sat in the ctr?

Cheers
Click to expand...
Mine is a 2001 Defender 90n with the 15P engine the engine temp display is not an analog read out as in most cars they only show the temperature in blocks which are sent by the ECU i.e. it reads cold until it hits a certain point then it shifts to just below normal, then moves up to normal, I cant be 100% sure but I read by the time it decides to move the needle up to red its already overheated.
I thought about that and decided I would like to add a bit more help so I bought this:
http://www.ebay.co.uk/itm/DC-12V-32...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649
I haven't manage to install it yet but its on the list, I may try and plumb it into the fuel pressure regulator too to look at the delivery pressure from the tank pump, either that or use it for the more obvious oil pressure monitoring.
 
I ran a td5 dicco for 4 years and 50k miles all over uk/europe, never heard the viscous fan come on until i fitted a bigger intercooler and from then on it was a regular occurrence, some time later back to std cooler and guess what? the fan stopped switching in.
So in conclusion I dont reckon theres much margin for error regarding the cut in temperature.
Plus of course if you also have a/c thats another air flow restrictor.

200 no fan no issue except in extreme situations
300 no fan needs keeping an eye on
td5 no fan be careful have you seen cyl head price?
tdv6 no fan dont even go there, engines very expensive, plus the fan hub is speed sensed and I think can also lock up on demand from the ecu.
 
On mine there is quite a difference when the fan is locked on, the thing roars but that's what I can hear with the bonnet up, that's how I found my first one was duff it was on all the time until I played with the little bi metal strip in the middle.
Cant say I notice it when traveling but maybe it never cuts in.
 
neilly said:
How did you hear the fan come on? surely it is always turning?

Cheers
Click to expand...


Its always turning but its practically freewheeling until the centre unit senses the flowing air is at a set temperature then the viscous unit starts to lock up and drive the fan hard and this is what you can hear.
Same as when car started from cold, the oil in the viscous unit has settled overnight and when you start the car and drive off the fan is driven hard for a few hundred yards until the oil sorts itself out then it goes back to freewheel mode.

I reckon most viscous fan cooling is passive ie its moving some air when its freewheeling especially at low speed ie town work and this is generally enough to keep things in check, its only when the going gets hard that its really needed.
 
raywin said:
On mine there is quite a difference when the fan is locked on, the thing roars but that's what I can hear with the bonnet up, that's how I found my first one was duff it was on all the time until I played with the little bi metal strip in the middle.
Click to expand...

Yes, have noticed this on the TD5 D2 my Dad just got, it does "roar" more than mine does. Will be keeping an eye on it in the short term.

Cheers
 
neilly said:
Yes, have noticed this on the TD5 D2 my Dad just got, it does "roar" more than mine does. Will be keeping an eye on it in the short term.

Cheers
Click to expand...
As Lynall says above when the motor has been standing and you start it up the fan seems to drive but when the engine has been revving it then goes to freewheel mode, it seems to do it more in the cold when the viscous liquid in the hub is thicker and settled in the hub.
If you start the engine with the bonnet up it will roar and you can feel the air moving, take it for a short spin and then pop it open again and you can hear the difference , this is also when I can stop mine with a roller up piece of cardboard.
 
@raywin

Yes, I understand how a VF works, My initial question was regarding when lynall said he could hear it turn "ON", I was just after a confirmation of what he meant , as it is already turning. It is more of an engagement action.

Cheers
 
my fan stated to roar a few times towing in europe when travelling slow up mountaiins, as i would hope suggesting viscous is in good condition,ive experienced some that roar frequently which would suggest either its getting hot or viscous is seizing ,similarly others that wont lock up however hot engine gets a new viscous isnt that dear
 
lynall said:
I ran a td5 dicco for 4 years and 50k miles all over uk/europe, never heard the viscous fan come on until i fitted a bigger intercooler and from then on it was a regular occurrence, some time later back to std cooler and guess what? the fan stopped switching in.
So in conclusion I dont reckon theres much margin for error regarding the cut in temperature.
Plus of course if you also have a/c thats another air flow restrictor.

200 no fan no issue except in extreme situations
300 no fan needs keeping an eye on
td5 no fan be careful have you seen cyl head price?
tdv6 no fan dont even go there, engines very expensive, plus the fan hub is speed sensed and I think can also lock up on demand from the ecu.
Click to expand...
My gauge has never gone to half way it always stays below. My defender is an XS model and also has a/c.
 
Scooby22 said:
My gauge has never gone to half way it always stays below. My defender is an XS model and also has a/c.
Click to expand...

Yes thats std for a std car gauge as they are not linear, ie they dont go from 0 to 120, more like 50/60 to 120 and the ok zone where the needle sits in the middle will be quite large probably from 80 to 110 ish, so being in the middle can vary hugely and you never really know how close to the limit you are until its to late.
A capilliary or digi gauge will tell you exactly whats going on and you will be amazed just how much the temperature fluctuates.
 
neilly said:
@raywin

Yes, I understand how a VF works, My initial question was regarding when lynall said he could hear it turn "ON", I was just after a confirmation of what he meant , as it is already turning. It is more of an engagement action.

Cheers
Click to expand...

First long hill after fitting the fat intercooler as I crested the top the roar was pretty loud and as this was my daily route for 9 years I knew what and where things were going to happen, so the roar took me by surprise.

The trucks are viscous with electronic speed monitoring and can also be switched on/engaged/activated by the ecu, if you use the intarder (awesome bits of kit) the ecu knows the cooling system is going to be working hard so will pull the fan in early to keep temperature in check
 
lynall said:
The trucks are viscous with electronic speed monitoring and can also be switched on/engaged/activated by the ecu, if you use the intarder (awesome bits of kit) the ecu knows the cooling system is going to be working hard so will pull the fan in early to keep temperature in check
Click to expand...

That does not sound like my D2.....................:p:p:p


Cheers
 
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