Water crossings.

The idea of the tarp is to create a dam effect, producing a bow wave which in fact pushes the water in front of you, and not have it slurping up around your engine. Naturally, this means you don't stop as you move through the water (if you can help it ...).

Have not heard of tying up the radiator fan before, but I am aware of instances where the fan has been sucked into the radiator during water crossings. If I was worried I'd probably disconnect the fan belt, but others may have more imaginative solutions to that one.

I have been lucky .. done a few water crossings, but always as a last option and I will drive miles (kms) to find a more shallow way through. Seems easier to drive than to repair.

Safe travels
Jack

Being a novice myself... I learnt all I could before "practicing"....

Always try to find the shallowest route.
Always walk the crossing first...... obviously only if it ain't croc/alligator/piranha infested.
Keep a constant speed and keep the "bow wave" happening
Never, repeat NEVER change gears while your running gear is submerged.
Don't try to go too fast, you run the risk of the radiator fan "propelling" forward into the radiator!

Hope this all helps!!

Tieing up the fan could lead to damage of the viscous coupling & on the majority of cars is totally unneccesary. On a diesel fitted with a snorkel, water splashing around the engine bay makes no difference. The chance of a viscous fan going through a radiator on a river crossing is remote (never seen 1) and easily resolved by fitting a tarp.
Tarping up is particulary usefull on petrol cars to stop water splashing over the spark plugs & distributer or to stop excess mud through the altinator etc in deep bog holes. Cheers Craig...............

You never have to worry about the fan unless it is a fixed blade type ie no viscous coupling. The viscous unit stops with the weight of the water hitting it where the fixed one acts as a propellor and usually goes through the rad.

I have a fixed fan on my LR 110

I usually undo the tensioner bolt on the alternator so the fan belt can slip if it has to before crossing deep water. Have had it over the bonnet no worries with this technique. Never bothered with a blind

James, tarping up is your best option, for the reasons mentioned above. Do that (and it's simple) and you won't have to worry about the fan.

A few more tips:

Take a break before doing a water crossing, if have the time. It will give the brakes and diffs time to cool down a little and possible avoid warping disks and sucking a bunch of water into the diffs.

Most water crossing are bests tackled in second-low and at a walking pace. That maintains a nice, steady bow wave and gives you the best chance of climbing out the exit if it's a bit tricky.

And, as the others have said, look for the shallowest, firmest crossing, whilst keeping in mind the TreadLightly principle.

I can see that tarping will prevent water coming straight through the radiator into the engine bay at the speed the vehicle is travelling, but I can't see that it will have any effect on the water that enters the engine bay from underneath the vehicle during a long deep crossing. So it won't prevent the slow immersion of the engine bay contents (including the fan). To get a picture of what I mean have a look behind the vehicle as you drive through water slowly - there isn't a nice deep track where the vehicle has bow-waved the water aside because it fills in instantly. Same with the tarp. If you could see inside the engine bay you would see the water filling from behind where thge tarp stops.
As for the viscous fan slipping when it hits the water, it doesn't. If the engine is hot the fan is engaged and the water won't make it slip.
Cooling fans propellering are problems seen on 100 series LCs and TD5 discoveries (now remedied by new fans with blades that won't flex forward).

I don't know about you guys but 99% of water crossings iv done have a rocky bottom & its hard to keep up a bow wave as you travel too slow.

With that in mind i wouldn't just rely on the tarp method, use it as an extra precaution.

I recently crossed a very muddy bog hole with 18" of muddy water.I was a little sloppy with the way I fitted the blind and got a lot of silt into engine bay.

When I got home I found that I had to hose the radiator core out from both directions under high pressure none stop for 15min, before it flowed through clean.
It certainly highlighted that if I had failed to spend the time hosing it out, the amount of silt in the radiator core would have significantly reduced it's effeciency.
Regards
Joe