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Old 11-15-2013, 06:50 AM
BMR_LVR's Avatar
BMR_LVR BMR_LVR is offline
Humble E34 lover
Location: Asheboro, NC
 
Join Date: Dec 2008
Posts: 5,508
Mein Auto: 1992 525i
Well, I used to think the newspaper test was a solid test. Not so much anymore. Let me explain (this assumes a correctly functioning fan clutch).

When stone cold, the fan clutch will be engaged, i.e. turning almost 1:1 with the crank. As the engine warms up, the fan clutch will disengage, i.e. turn slower than the crank. This in essence is the function of the clutch; to not turn as fast when not needed, i.e. when the engine is at normal operating temp. So, if you stick the newspaper in the fan when the engine is only at normal operating temp, the fan will stop rather easily. I know this because I tested it when I recently put a new fan clutch on. I then did a complete coolant system overhaul about 5K miles thereafter as preventative maintenance. It had been 80K since my previous overhaul. So, I know that the fan was new and the cooling system was new and functioning properly.

Moving on, if the engine temp exceeds normal, that is when the viscous clutch will begin to engage and cause the fan to turn faster thereby drawing in more air across the radiator to assist with cooling the engine back to normal temp. This can happen on a hot day in stop and go trafice. I'm sure many here have had the experience of being in traffic, taking off and hearing the fan roar for a few seconds (10-20 seconds) and then quiet down again. This is the normal operation of the fan clutch.

So, having said that, the newspaper trick would really only work if the engine temp was up to the point that the viscous material in the clutch is hot enough to engage and turn the fan faster. So, if your engine is at normal operating temp, the fan will be stopped by the rolled up newspaper. Now, if the engine is running hotter than it should (say anything above 12 o'clock and up to 3/4), then the fan should indeed shred the newspaper if it is operating properly.

So a synopsis of a normally operating fan clutch:

Engine stone cold - fan clutch engaged
Engine at normal operating temp - fan clutch disengaged (easily stopped with the newspaper)
Engine above normal operating temp - fan clutch engaged
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Quote:
Originally Posted by noego View Post
It's Deja Poo - as in, I've heard this **** before.
Steve

Calypso Red 1992 525i with 225K miles

1991 735i - Sold
1992 525i - Sold
1995 325is - Sold
2000 528i - Sold

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