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Thread: Viscous fan question

  1. 17th March 2006, 01:42 PM #1
    Omaroo's Avatar
    Omaroo
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    Viscous fan question

    Hi all

    I'm cruising along a motorway doing 100 or 110 for a while and then stop for a couple of minutes (like for a fillup or to wait for someone). I then continue a couple of minutes later and try to get back to freeway speed and the fan sounds like it is spinning at engine speed - i.e. I have no power and the fan is pulling a gale through the radiator.

    Is this normal behaviour? After a while I get to 100/110 and it seems to settle again - but getting to that speed back up through the gears is laborious...

    Any ideas? Is this "normal"? Sounds like the viscous clutch is locking when it's hot and not releasing again for a long time even though their is air hitting the radiator at freeway speed...
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  2. 17th March 2006, 06:15 PM #2
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    Ralf_the_RR
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    I can't see the fan sucking that much horsepower to prevent you getting up to speed.
    There is something else wrong.

    I have my fan locked permanently (long story - don't ask), and it gets to 110 quite easily.
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  3. 17th March 2006, 07:19 PM #3
    PhilipA
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    There are probably 2 things.
    -heat soak in the engine bay increasing the temp to lock up stage.
    -when stopped the silicone fluid falls to the bottom and pools. This is more noticable when cold. Ever heard a Rangie when first started?
    If you are getting major heat soak, maybe you should look at some more vents to let the hot air out. After all the cabin of a Defender has built in vents,from the many leaks.
    What sort of car. Classic Rangie?
    Regards Philip A
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  4. 17th March 2006, 09:06 PM #4
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    Omaroo
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    No, a '00 Defender Td5 Philip
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  5. 17th March 2006, 09:52 PM #5
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    akitda
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    Hi,

    I have got the same problem as you have described. I have noticed that when I was driving from Mel to Syd last month on a very hot day (38+ degree). The coupling fan just same working continousuly and "sucking" half of the engine's power. By the way, I am having a td5 90.

    Cheers,

    Greg
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  6. 18th March 2006, 06:41 AM #6
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    Apart from the mud-related problems, is it time to go electric?
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  7. 18th March 2006, 06:59 AM #7
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    Captain_Rightfoot
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    I drove up to an island in December last year... 1000k. It was hot- between 35 and 40.... and we were cruising at 110 - 120 and I too noticed that the fan would come in quite often, and it made much noise, and you could feel the drain on the engine.. I though it was just me. 8O
     2005 Defender 110 
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  8. 21st March 2006, 07:28 AM #8
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    someone (an Aussie, can't remember who) on one of the Pommy forums was having overheating problems with their Tdi Deafener at speed, and it turned out to be a buggered viscous clutch. Installed a new one and no more problems.
    The ram air effect obviously isn't working, meaning that the air isn't getting away from the underbonnet area. Remember that for air to flow it needs a pressure differential, ie, it only flows from a region of (relatively) high pressure to a region of lower pressure. If the underbonnet air pressure is too great, it will need either extra venting (NOT at the base of the windscreen, this is also a high pressure area) or mechanical assistance, hence the fan locking up to pull more air through and force it out of the engine bay area.

    I'm about to embark on the bonnet venting scheme on a TD42T GU Patrol. These things are known overheaters when towing and they have a massive radiator. I've only got as far as wool tuft testing to work out the best position, and proved that the base of the screen is a high pressure area when the tufts folded back under the trailing edge of the bonnet. This is why they used a rear opening bonnet scoop back in the A9X Torana and XC Falcon Hardtop touring car days.
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