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Viscous fan versus electric fan

Posted: 07 Aug 2011
by mat_the_cat
Something to ponder - on the Discovery someone has removed the standard large viscous coupled engine driven fan and replaced it with a pair of smaller Kenlowe units. As standard it also has two electric fans which come on with the air conditioning or with a thermal switch on the block. This has been disconnected and used to trigger the Kenlowe fans.
To me, this is not ideal for a number of reasons. Firstly, the Kenlowe units have about the same flow as the old engine driven fan, so now the total amount of cooling air available is less. The additional fans are almost always on when climbing hills. When in traffic, there is no airflow through the engine bay when the fans aren't running, so underbonnet temperatures get higher, also they seem a but unreliable. Even with 40A relays they seem to fail - usually on continuously but once didn't come on. Lastly, LR could have put an all electric system as they had the thermal switch in place, but chose to have main cooling with the engine fan, so there must be a reason.
Should be a simple job to whip the viscous fan off the old Disco, and put it on the new one, then reinstate the wiring to the standard electric fans. There doesn't seem to be a difference with economy, so I can't see any downside! Any thoughts? As a bonus, I might be able to get a few quid from selling the Kenlowe fans on eBay...

Re: Viscous fan versus electric fan

Posted: 07 Aug 2011
by docchevron132
Merc do the same. The viscous fan is very useful for keeping air moving through the engine bay continually, which better regulates the under bonnet temps, rather than having fans that switch in and out. Leccy fans running at road speeds over 30MPH can actually make the engine hotter as it fucks up the air flow through the rad.
So yes, I'd reinstate the viscous fan and use the original fans for what they were intended, IE air con and extra cooling when required only.

Re: Viscous fan versus electric fan

Posted: 08 Aug 2011
by Philhod
Wat ee sed. The system was designed for optimum service on that vehicle.

In my experience, fuck around with it at your peril, unless you know you can improve it. 8)

Re: Viscous fan versus electric fan

Posted: 08 Aug 2011
by mat_the_cat
My thoughts exactly, but it is a common mod on these vehicles. :roll: The other problem is the original mechanical fan (which was almost the size of the rad) had a shroud directing the air all over the radiator. The additional electric ones cover about 2/3 of the rad, but their airflow is only on the parts actually covered by the fans. Not an improvement in my book! [no]

Re: Viscous fan versus electric fan

Posted: 08 Aug 2011
by docchevron132
sounds like whoever fitted the Kenlowe's bought what they could afford without thinking about airflow or coverage..
If you want EPIC cooling, I have a spare hydraulic fan off the bus. Although you may hve to cut a hole in the bonnet for it!

Re: Viscous fan versus electric fan

Posted: 08 Aug 2011
by Vanny
Thirded, go have a look under a recent LandRover and you'll likely find viscous AND electric, both for very good reasons.

It's also worth considering a latching kill switch on the elctirc fans for wading. High speed electric fan + water = fucked blades imho.

Re: Viscous fan versus electric fan

Posted: 08 Aug 2011
by Way2go
Vanny wrote: It's also worth considering a latching kill switch on the elctirc fans for wading. High speed electric fan + water = fucked blades imho.
Might be better to fit a float switch in that case. :)

Too much to remember too late, comes to mind otherwise. :wink:

Re: Viscous fan versus electric fan

Posted: 08 Aug 2011
by Philhod
I have a spare hydraulic fan off the bus. Although you may hve to cut a hole in the bonnet for it!
:lol: :lol: :lol: And then you wouldn't be able to see where you were going and the heater would be permanently cold. :lol: :lol: :lol:

Re: Viscous fan versus electric fan

Posted: 08 Aug 2011
by Way2go
Philhod wrote:
And then you wouldn't be able to see where you were going
Not necessarily, Spitfire pilots could see through their propellers. :P
(And they could fire their guns through them due to synchronisation! :wink: )

Re: Viscous fan versus electric fan

Posted: 08 Aug 2011
by mat_the_cat
Surely it would have been better to mount the guns on the propeller itself so that instead of having to aim them, all he'd have to do is draw alongside (or above/below) the enemy, and fire!

Re: Viscous fan versus electric fan

Posted: 09 Aug 2011
by docchevron132
with only 8 seconds worth of squir from a Spit, you'd want to make sure the blade was pointing the right way at the time!

Re: Viscous fan versus electric fan

Posted: 09 Aug 2011
by Vanny
Way2go wrote:Too much to remember too late
Got to say, everytime i've waded a car its never been an instantaneous thing, usually long winded preparation of checking the breathers, puting the recovery gear on the bonnet (saves swimming under the car later), ensuring a few more 'able' characters have made it across first, i'm sure i'd think to turn the fans off.

But i love the idea of a float switch!

Re: Viscous fan versus electric fan

Posted: 09 Aug 2011
by mat_the_cat
Whenever I've been wading to that sort of depth the fans have never come on (mind you with the viscous fan on the old one the electric fans only came on once, and that was on a steep hot climb in low first). But I like lots of switches, so I'll probably fit an isolator on the dash.

Re: Viscous fan versus electric fan

Posted: 09 Aug 2011
by Philhod
Talking of switches Mat, I mounted that one you gave me in the blank panel,opposite side to the coin tray.

Must say it looks the dogs there. Will have to study the wiring diag and connect to the lights next.
I decided to repaint the black round the window frames,sill edges and have included the air vents and the rear spoiler. Must say it looks great now it's finished.

Re: Viscous fan versus electric fan

Posted: 20 Sep 2011
by mat_the_cat
Fitted the viscous fan (and sold the electric ones for £53 on eBay!) and the standard electric ones barely come on. They did once after towing a couple of tons of hay up a hill, but not yet when solo. That must mean that the overall engine temperature is now lower even though the point at which the temperature gauge takes its reading from is roughly the same (the gauge never moves off halfway no matter what you do).

Re: Viscous fan versus electric fan

Posted: 20 Sep 2011
by docchevron132
bet I could make it come on!

Re: Viscous fan versus electric fan

Posted: 20 Sep 2011
by Philhod
:lol: Hot stuff Eh!

Re: Viscous fan versus electric fan

Posted: 20 Sep 2011
by Vanny
TC in the top and bottom hose and coolant inlet hose (you can put them into fluid between the metal pipe and the rubber), then log them. You must have access to this shit no|?

Re: Viscous fan versus electric fan

Posted: 20 Sep 2011
by mat_the_cat
Yeah, I've got access to a few things that might do the job…but without a point of reference as to how it was before, there doesn't seem much point. What would be more interesting is the temperature drop across the BX intercooler before and after a bit of quick driving. I'm sure I can detect a drop off in performance. Am I right in thinking that in the early days of the BX Project there was a guide to making a water cooled intercooler using one of the washer bottles? Or was that a (strange) dream?

Re: Viscous fan versus electric fan

Posted: 20 Sep 2011
by Vanny
Your not mistaken it was there. Might dig it back out later, unfortunately i'm not allowed upstairs as she's on nights and sleeping!