ask again about viscous fan on diesel GQ

Submitted: Friday, Mar 21, 2003 at 23:19
ThreadID: 3986 Views:1238 Replies:3 FollowUps:2
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Sorry guy! I know this topic has been discussed over and over again. I hope you won't feel annoying to my question.
I find that my fan run as fast as the engine at cold start. Shouldn't it run slowly and getting faster and faster once it warm up ?
I have changed thermostat, water pump and coolant 3 months ago. Normally it take 10mins idling to warm it up to "C" mark. Normal temp guage about 1/3
Is my fan working properly ?
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Reply By: Will - Saturday, Mar 22, 2003 at 15:53

Saturday, Mar 22, 2003 at 15:53
IAMGQ, probably the simplest way is to ask some one that has the same model and ask them to show you theirs ,(with a smile on your face).
See if theirs does the same under the same conditions.
I think you will find that the fan will only turn much slower at revs when the air flow through the radiator pushes against the natural flow direction of the fan. Meaning the flow of air retards the rotation of the fan. When the motor is hot the resistance to this retarding motion is greater meaning the fan will turn more, thence flow of air through the radiator from your forward motion plus the fan turning means more air.
The fan will always turn more at low speed because the motor will always run a little hotter at idle and you have no air flow to stop the fan rotation.
I hope that helps or have I made it worse.
AnswerID: 15856

Follow Up By: IAMGQ - Saturday, Mar 22, 2003 at 22:59

Saturday, Mar 22, 2003 at 22:59
Thanks Will
I think I understand what you mean.
FollowupID: 9693

Reply By: Truckster - Saturday, Mar 22, 2003 at 19:51

Saturday, Mar 22, 2003 at 19:51
When you first start the car the fan should run as though the car is HOT....

Then after a 30seconds - minute it should slow down.

When Hot there should be resistance in the fan slowin you from turning it.

When cold it should freewheel easier.

If in doubt goto a radiator place, 4wd store, Nissan dealer, or your local 4wd club and ask somene there.
AnswerID: 15877

Follow Up By: IAMGQ - Saturday, Mar 22, 2003 at 23:01

Saturday, Mar 22, 2003 at 23:01
Thanks Truckster, Will check it tomo.....
FollowupID: 9697

Reply By: colin - Sunday, Mar 23, 2003 at 20:26

Sunday, Mar 23, 2003 at 20:26
the silicne in the hub runs differently to your normal way of thinking, the hotter the radiator the stiffer the silicon so the more the fan runs, but it also has a lot to do with the coil spring which helps cut in the hub at a set temp. Thats what Trucky paid $80 dollars for at Berrimah Diesal. Col
AnswerID: 15933

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