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Phillywilly72



Member Since: 29 Apr 2024
Location: Wiltshire
Posts: 45

United Kingdom 2011 Defender 110 Puma 2.4 DCPU Tamar Blue
Radiator Fan Immediately On
New owner of a 2011 110 dcpu. On cold start the radiator fan starts with engine. Are they viscous and so should only kick in when temp reached or can there be a dodgy sensor somewhere. Would like to diagnose this myself. Any help appreciated cheers Phil.
Post #1033230 29th Apr 2024 10:46am
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Ianh



Member Since: 17 Sep 2018
Location: Essex
Posts: 1972

United Kingdom 
As standard the fan will be a viscous fan , although someone could have replaced it with an electric fan. It’s easy to tell which one you have with the bonnet open, if not sure post a picture and members will confirm.

A viscous fan is a self contained unit, with no input from external sensors. In essence it uses a bimetallic coil, that when heated allows fluid to fill a gap between two plates that then causes the fan to rotate.

The fan can free rotate with engine running but if working properly does not engage more unless the airflow over the bimetallic coil reaches the right temperature.

From what you say , if it’s a viscous fan, it is working as normal.

This is well worth a read on the subject. https://www.defender2.net/forum/post754068.html
Post #1033239 29th Apr 2024 11:58am
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hank



Member Since: 12 Sep 2016
Location: South Wales
Posts: 2290

Wales 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
Double check which fan is going.
The engine coolant fan is viscous.
The air conditioning condenser fan is electric - you can see this one behind the front grille > 110 XS Double Cab
Post #1033240 29th Apr 2024 12:00pm
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Mo Murphy



Member Since: 01 Jun 2008
Location: Letchworth Garden City, Herts
Posts: 2214

United Kingdom 1984 Defender 90 BMW M57 3.0 Diesel HT Auto Pennine Grey
The viscous fan will always rotate with the engine but its basically just freewheeling until the hub locks up.
Mo The Land Rover 90 - Many are called, few are chosen.

50 Shades of Pennine Grey
Post #1033256 29th Apr 2024 2:22pm
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Phillywilly72



Member Since: 29 Apr 2024
Location: Wiltshire
Posts: 45

United Kingdom 2011 Defender 110 Puma 2.4 DCPU Tamar Blue
I don’t have air con and if the rad fan goes at full whack on startup, I suspect it’s seized. I’ll try the newspaper method first. Also will a viscous freely rotate if I hand spin it switched off and cold?
Post #1033266 29th Apr 2024 3:35pm
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andy63



Member Since: 30 Jun 2023
Location: north east
Posts: 497

United Kingdom 
The fan may well make a bit of a roar at start up.. But it should revert to a quieter tone fairly quickly.. If there is fluid still in the coupling when you start it takes a few seconds for it to be forced back into the reservoir..
I'm sure this has already been mentioned but if you use a bit folded newspaper it should be possible to stop it rotating fairly easily when cool.. When warmed up and connected it will be difficult to stop if it's working properly.. I'm sure you could use a hot air gun to carefully connect the coupling by actuating the valve 👍
Post #1033269 29th Apr 2024 3:53pm
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MadTom



Member Since: 10 Sep 2013
Location: Olomouc
Posts: 615

Czech Republic 1999 Defender 130 Td5 HCPU Baltic Blue
Just small detail - when the mechanical engine fan is on full power (with viscous clutch engaged), it sounds like a small helicopter, and with hot engine you will feel hot wind on your feet standing behind the car. Is is much more powerfull than standard electric fan. "Drobek" = The Small One - Discovery 2, "Blufínek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo Smile
Post #1033357 30th Apr 2024 7:31am
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