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Driving through flood water - how deep can you go?  
Driving through flood water - how deep can you go? - *Gongfarmer*
During monday mornings ridiculous weather I spent 2 hours never getting to work. At one stage on the flatlands of the Fylde I drove for several hundred yards up a flooded lane lane that got steadily deeper. I was following a Hi-Lux and watched in horror as the water got ever closer to his bodywork. I this the same technique in flood water; select 1st gear, enter slowly then build up speed gently to create a bow wave. I reckon I was in 12 - 15" inches of water when panic set in, I didn't dare lose speed by turning round, eventually I found a farm drive that climbed out of the water where I turned round and retreated, discretion being the better part of valour! but what would happen if it had got deeper, what's the danger ? The ignition system is as high under the bonnet as it could be, so is it water entering the engine block through air intake or elsewhere?

Tags: technical issues leaks gearboxes 4x4s

Driving through flood water - how deep can you go? - movilogo
Is it not up to the ground clearance level height?
Driving through flood water - how deep can you go? - pyruse
If water enters the air intake, the engine is toast.
If you stall when the exhaust is under water, you will never restart until the car is pushed/towed out of the water.
If the water is deep enough, the car can be swept away.
It's easy to drive into a ditch because you can't see the edges of the road.

That's all the hazards I can think of.
Driving through flood water - how deep can you go? - Lud
>>
That's all the hazards I can think of.


If you wet the engine electrics thoroughly enough, a petrol engine will stop even if it hasn't ingested water through the intake (which will bend or break conrods or break the crankshaft). It won't start again until everything is dry, and perhaps with a modern engine - someone else will have to confirm this - the electronics will have suffered irreversible damage.

Suddenly immersing a hot turbocharger in cold water may crack its casting.
Driving through flood water - how deep can you go? - deepwith
Last week a friend followed other cars through flood water on her return home - having been through it 2 hours before. She drove out the other end and drove round the corner to find an AA van and several cars - at this point her car also stopped. Insurance company have written it off - a 2 year old mini which needs nearly £5,000 spent on it.
Driving through flood water - how deep can you go? - Spospe
If water gets drawn into the air intake, normally the air filter will prevent it reaching the engine. The engine will naturally stop, due to a lack of air (oxygen), but will not suffer direct mechanical damage. However, do not attempt to restart, get towed out and let the car drain, followed by opening the air filter to clean / dry it and turning the engine over with the plugs out (petrol) or the injectors (diesel). If the injectors are difficult to remove, try pushing the vehicle gently in top gear so as to turn the engine over and expel any water.

How deep can you go? It depends on the vehicle and how fast you drive. I have been deep enough for water to flood in through the doors over the sills (Rover 216) and there was no problem at all.
Driving through flood water - how deep can you go? - doctorchris
The number one issue is the height of the engine's air intake. If this sucks in water the engine "hydraulics", ie it ingests an incompressible medium, water, and serious damage results. Some cars have ridiculously low intakes, most off-road vehicles are more sensible and I'm sure you have seen such vehicles with snorkels that give amazing wading capability.
I've never found a relatively brief drowning of the electrics to cause problems, though I did take a petrol-engined 1993 Maverick repeatedly into muddy water which eventually deposited enough muck into the alternator to prevent the brushes contacting. Cleaning out the alternator remedied this.
Other than this, oyu don't want to put too much pressure on your door seals as dirty water will make a mess of your car's interior that would be hard to clean.
Driving through flood water - how deep can you go? - PhilW
There is another aspect. Near us a couple of roads used to flood regularly. One was next to the river after a bridge and usually had quite a strong current. When water here got up to the sills , the car would start to "float" and lose grip on the road and be swept sideways - dangerous because of deeper ditch at side of road. The other road would flood with virtually stagnant water - there one only had to worry about the air intake height (we had an old BX diesel at the time) and could go through deeper water - especially with the suspension set on "high"! I think the air intake on BXs was high up in the wing above he front wheel - but floating was the main problem!
Local kids used to make good money pushing stranded motorists out! One lad, after watching the BX go through asked my son to ask me to drive through repeatedly "leading" other cars so they got stuck!
Driving through flood water - how deep can you go? - Screwloose

Where did the nonsense about a bow-wave come from? That's just about the worst thing you could possibly do; many air intakes are in ludicrous places like the top of the bumper.

Creep through standing water trying not to leave even a ripple; walking pace is far too fast. [Specialist wading-prepped vehicles excepted.] Flowing water is near-lethal; think of it as a liquid landslide, the moment it reaches the floor, you're driving a rudderless boat - that's going wherever the current takes it.

I've never seen an airfilter stop floodwater yet and even a little sucked in will destroy the engine totally, particularly a diesel. Despite all the references in books; in dozens of cases, I've never seen water sucked back up an exhaust and they seem to start OK with the end immersed too.

Gritty water getting into the alternator ruins the bearings; if it gets into the clutch housing it takes out the release bearing and the starter and scores the rear oil seal seat on the crank. Immersing warm gearboxes and diffs in cold water causes sudden contraction of the air inside and sucks water in through the breather tubes.

All told; modern cars are just not cut out for wading. Open the window and watch the front wheel; whatever you're driving, once it's up to the wheel centre - back it out.

Driving through flood water - how deep can you go? - PhilW
Screwloose,
With you on all points except "whatever you're driving, once it's up to the wheel centre - back it out." Hydraulic Cit will go a little deeper - but not a lot! (3 inches??) Open to contradiction!


Driving through flood water - how deep can you go? - retgwte
managed about 4 or 5 foot in a hire car the other day, just went for it

about 2 or 3 foot in my own

:)

surprising the number of people who dont know how to drive through water, if youre risking it you may as well improve the odds by doing it well, and the number of people who stop dead in the deepest part!



Driving through flood water - how deep can you go? - PhilW
"managed about 4 or 5 foot "
Surprised you didn't get a leak through the sunroof - what car was it? - or do you mean you got 4 or 5 foot into the flood before car stopped?
Daft - even a tank would struggle with 5 foot of water.
Driving through flood water - how deep can you go? - oilrag
No more than 2 inches in my case ;)

Years ago I went through about a foot deep and later had the wheel bearings failing one by one.

That was the petrol automatic Maestro that did 23MPG and had very severe metal cracking on the camshaft lobes when I peered in with a view to checking the clearances.

Thank you for holding on, metallic blue Maestro, DCX ++++, a `pigeon returning to roost` (condition undetected) at a Rover dealer`s used car lot in the early 90`s. ;)

Regards

Edited by oilrag on 23/01/2008 at 19:27

Driving through flood water - how deep can you go? - Screwloose
managed about 4 or 5 foot in a hire car the other day just went
for it


I didn't know that you could hire a Scammell Explorer.....
Driving through flood water - how deep can you go? - Screwloose
Phil

As you're changing the ride height to above the surface; that could be an exception - might not do the wheelbearings much good if prolonged though; car oil-seals are mainly designed to keep grease in.....
Driving through flood water - how deep can you go? - Number_Cruncher
>>I've never seen..

My experience of this is exactly the same.

If anyhing, I would go a bit further, and suggest that once you are into water that's more than a 4 inches deep or so, back out, and find another route.

Where does the water going back up the exhaust pipe myth come from?

Number_Cruncher


Driving through flood water - how deep can you go? - Susukino
"All told; modern cars are just not cut out for wading. Open the window and watch the front wheel; whatever you're driving, once it's up to the wheel centre - back it out."

This advice is undeniably valid in a kind of "you won't have any regrets" kind of way, but it's a bit overblown. My house is at the end of a long unpaved muddy track through a wood in west Wales, with a ford halfway down the track. The water is usually about 6 inches deep and when we've had really heavy rain (i.e. fairly often in this part of the world) it quickly gets to double that.

We go back and forth every day in a Toyota Yaris diesel which has, I think 14-inch wheels. When the water is really deep then we don't chance it but I've certainly been through a foot of water many times - that's significantly deeper than the 7 inches that would mark the midpoint of the wheel. I just stick it in first and surge through the ford. Three years after buying the car it's still in great condition and has (touch wood) never gone wrong or let us down. The people who owned the house previously had a Fiesta. I can't imagine that most 4x4s or even soft-roaders wouldn't fare a lot better than the Yaris and the Fiesta. On the other hand I certainly wouldn't try entering ANY piece of water unless I was intimately familiar with the ford or bit of flooded road in question!

Just my tuppence worth, but based on daily experience rather than the occasional encounter with flood waters.

Suss
Driving through flood water - how deep can you go? - Chad.R
The Yaris may have 14 inch wheels but with the tyre the total diameter would be close to 2ft.

So halfway up the "wheel" would be about a foot of water.
Driving through flood water - how deep can you go? - Susukino
"The Yaris may have 14 inch wheels but with the tyre the total diameter would be close to 2ft.
So halfway up the "wheel" would be about a foot of water."

Thanks, that's an excellent point - I never thought of that because I don't bother to look at the wheels, I just trundle cheerfully through the ford. The various depths of the ford as reported are accurate; in the early days I would get out of the car and paddle around in my wellies in the water to check the depth, but I seldom do that now that I'm used to it.

It does suggest that Screwloose's comments about avoiding anything above the midline of the wheel + tyre are less conservative than I initially thought.

This probably also explains in part why many people in my neck of the woods drive Land Cruisers, Land Rovers, Patrols and battered old Izusu's.

Suss
Driving through flood water - how deep can you go? - pendulum
The air filter housing on my ZX is I think the lowest part of the vehicle other than the wheels. The intake is at the front and quite low as well. I'd dare not take it through any flood water. I've been known in heavy rain to avoid large puddles that have formed.
Driving through flood water - how deep can you go? - Aretas
Screwloose - I love your summary, the best bit being how to decide enough is enough. I will certainly remember the wheel centre tip.
Driving through flood water - how deep can you go? - oilrag
"managed about 4 or 5 foot in a hire car the other day, just went for it"

We went through 9 feet once by going for it in reverse and relying on cavitation to keep the air intake clear and personal gas to keep the cabin pressurized.

Driving through flood water - how deep can you go? - PhilW
"personal gas to keep the cabin pressurized"

You must have been on the Marstons Pedigree - it has that effect on me too!


Driving through flood water - how deep can you go? - bathtub tom
One of my cars has got the 'cat' under the car. The cost of a new 'cat' will buy an awful lot of petrol to find a suitable detour.
Driving through flood water - how deep can you go? - *Gongfarmer*
If drawing in water through the Air intake is the main danger, there may be a few boy-racers with regretting fitting those ground level cold air intakes !
Driving through flood water - how deep can you go? - retgwte
4 inches?

wow u not seen nothin have you

out in south west was it last week or the week before i forget i drove through very deep water, which was very unexpected, just flash flood i guess on top of already overflowing rivers etc, there would have been nowhere to turn round anyway, thin country road, and as soon as you go for it theres another car 10 foot behind doing the same, it was a A road as well (yes you do get thin A roads in the countryside) and I knew the people behind would get trapped so I called the fire brigade as soon as I found somewhere to park, the next day the police were blocking the road as it was circa 10 foot deep and nobody would have go through if they had started off down the road

last weekend slightly less deep water somewhere else I had a chance to turn round so turned round, surprising number of grannies going for it though

isnt it the focus that has a very low air intake for the cabin air? wouldnt like to be in one of those

none of this is the deepest ive been through though, was in a flash flood in the north east with my mother in the passenger seat, totally unexpected, overwhelmed the drains and boy was it like driving a submarine, just made it home which was on high ground thankfully :) them old cavaliers sure were good cars!



Driving through flood water - how deep can you go? - wemyss
At five foot surely the water level would have been higher than your head when seated in the car. Remarkable story and one I must remember.

wemyss
Driving through flood water - how deep can you go? - Screwloose
At five foot surely the water level would have been higher than your head


Seeing as most cars will start to float at around 18-20" must've had screw propulsion and rudders like an Amphicar.
Driving through flood water - how deep can you go? - Leif
>> At five foot surely the water level would have been higher than your head
Seeing as most cars will start to float at around 18-20" must've had screw propulsion
and rudders like an Amphicar.



A conning tower, and torpedo tubes more like ..
Driving through flood water - how deep can you go? - Leif
As I mentioned on a recent thread, a few days ago I was crawling through flood water, maybe 4" deep, in a Ford Ka. An idiot in a Land Rover on the other side of the road decided to take the flood at high speed, creating a large bow wave, and huge 2m high waves either side, which completely engulfed my car.

We have a local road in Luton which goes under a railway bridge, and it often floods so as to be impassable. I've seen a car or two stranded before.

I have to admit that it is only because of this site that I know how to drive through a flood (slowly with high revs) and to avoid anything but shallow ones.
Driving through flood water - how deep can you go? - Number_Cruncher
>>with high revs

What's the logic for high revs?

Number_Cruncher
Driving through flood water - how deep can you go? - retgwte
well you need to keep the revs high to keep the exaust pressure high, so you need to be in a lower gear than normal, and foot holding the revs up if changing gear

all to stop the water versus gas battle that will be taking place at the pipe opening

drive like normal and youre at much higher risk of stalling from water blocking pipe

also phycological affect mainly now, but on a car which could misfire or whatever having some momentum in the flywheel to keep the engine running would also reduce risk of stalling, less important in a modern well maintained car

sure there are other reasons?

Driving through flood water - how deep can you go? - Billy Whizz
were you driving this car?
www.youtube.com/watch?v=G3jcTVb4iSU
Driving through flood water - how deep can you go? - Number_Cruncher
>>water blocking pipe

I can't believe this bit. Engines will continue running (albeit not producing their full power output) with almost completely blocked exhausts, and the water pressure we are considering can't be great - 4" depth of water is equivalent to about 1% of atmospheric pressure.

Perhaps there should be a motor car edition of QI, where these long standing myths can be well and truly debunked. Ackerman steering geometry is another long standing bit of nonsense that I would like to see expunged from text books!

The flywheel angular momentum argument I do like though - being in a low gear does give your car more kinetic energy without giving it extra forward speed.

Number_Cruncher
Driving through flood water - how deep can you go? - Screwloose
retgwte

There is no battle; a modern engine is a very efficient air pump indeed and can easily produce 40 or 50 lbf/sq/in without even firing; [try holding your hand over the tailpipe and crank it....] There's no need to have the engine at anything but idle - you should only be doing about a quarter of an mile-per-hour so there will be no changing of gears needed.

As you're only going to be in a safe depth of water, there's no reason why you can't switch it off - if some idiot is coming the other way with a bow-wave the size of the Titanic it's a good move. Wait until it's a millpond again, start it up and resume your quiet progress. No stress - no rush.

Even if the complete exhaust were full, it wouldn't take many seconds for it to be expelled. Trust me; I've done enough breakdowns up to my knees in floodwater to know it works. A few squirts of WD40 and they usually started - in those days the air intakes were right on top of the carbs.

Edited by Screwloose on 23/01/2008 at 23:25

Driving through flood water - how deep can you go? - retgwte
dunno cold water inside the catalyst may make it crumble thesedays?

i dont pretend to have done any great experiments, but having watched cars driving through water for 40 odd years the ones that have got stuck have generally been the ones low on revs, and the higher reving ones more often made it, sort of becomes instinct from personal experience if you know what i mean

anyways we should run a test, anyone got a hire car at the moment?

Driving through flood water - how deep can you go? - pyruse
As you're only going to be in a safe depth of water, there's no reason why you can't switch it off - if some idiot is coming the other way with a bow-wave the size of the Titanic it's a good move. Wait until it's a millpond again, start it up and resume your quiet progress. No stress - no rush.
-------------------------
This hasn't been my experience. Last time I stalled a car in a ford (15 years ago), it wouldn't restart until it was pushed out, at which point it restarted at once. This was an old Nissan Bluebird.
Water over the exhaust certainly does stop some cars from starting.
Driving through flood water - how deep can you go? - ForumNeedsModerating
.. through flood water, maybe 4" deep, in a Ford Ka. An idiot in a Land Rover on the other side of the road decided to take the flood at high speed, creating a large bow wave, and huge 2m high waves either side, which completely engulfed my car.

4 inches? How can a large bow be created by 4 inhes of water? This in turn creates 'waves' of over 6 feet in height? Yeah, right... You got a bit splashed in in other words. Hyperbole at its finest!





Edited by woodbines on 24/01/2008 at 00:14

Driving through flood water - how deep can you go? - Leif
4 inches? How can a large bow be created by 4 inhes of water? This
in turn creates 'waves' of over 6 feet in height? Yeah right... You got a
bit splashed in in other words. Hyperbole at its finest!



Not a word of hyperbole. I simply described what happened, and I was genuinely expecting to be stuck. Watch a car go through a flood at speed, and you will see water thrown up, especially from a large vehicle such as a Land Rover. (Well, large compared to my motorised tea pot.)
Driving through flood water - how deep can you go? - spikeyhead {p}
I managed about 46 yards in a Citreon ZX TD

Unfortunately the puddle was 50 yards long

However, all it needed to get it going again was

A new

Turbo
set of con rods and crank shaft
Alternator
various bits of brakes
Assorted valves, I didn't bother to listen to the exact number that were replaced, though its entirely possible that the word "most" was used rather than a specific number.
all the fluids needed renewing, oil, antifreeze etc
exhaust

The above list isn't exhaustive, however its a sufficient reminder not to drive into a 50yard long foot deep puddle at 60mph. The effects of hydrolicking a turbo diesel engine are substantial. The car was sold very shortly afterwards, I doubt the new owner had a very happy ownership experience with that car.
Driving through flood water - how deep can you go? - Cliff Pope
Is the "cold water cracking a hot cat" story fact or fiction? If so, then even quite shallow puddles would present a risk.

The "water up the exhaust" story is total myth. Look at motor boats - you commonly see them with the exhaust burbling happily away with the outlet under water.
Unless perhaps you are reversing? That is always the moment for decision - the puddle looked shallow, but as the road progressed you realise it is getting deeper. At what point do you decide to stop, turn round, or press on and hope?
Driving through flood water - how deep can you go? - Chris S
This week there was an item on the news about a car being swept away as it crossed a ford outside Shrewsbury. The water was only about a foot deep but very fast flowing. I suppose water speed is as important as depth.
Driving through flood water - how deep can you go? - bignick2
" This week there was an item on the news about a car being swept away
the water was only about a foot deep but very fast flowing. I suppose water speed is as important as depth."

Don't forget that water is HEAVY - a cubic metre of water weighs 1000Kg (ie more than the weight of most small cars) if it is flowing at any sort of speed that is a lot of kinetic energy available for picking up a car and carrying it downstream.


Driving through flood water - how deep can you go? - Chris S
Is the "cold water cracking a hot cat" story fact or fiction? If so then
even quite shallow puddles would present a risk.

I've cracked an exhast in two after driving through a flood.
The "water up the exhaust" story is total myth. Look at motor boats - you
commonly see them with the exhaust burbling happily away with the outlet under water.

Is this the exhaust or the coolant out-flow? Many motor boats don't have radiators, they just sccop up water, pass it over the engine and then dump it out again.
Driving through flood water - how deep can you go? - Alan
I cant understand why an insurance company should be expected to pay out for a wrecked engine if someone drives into floodwater. Insurance is surley to pay for acidental damage or an unforseeable event such as fire or theft and then the insurancce company is often reluctant and looking for a get out.
Choosing to drive into water and have it sucked into the engine is completelty forseeable and as deliberate an act as deliberatly driving into a brick wall.
If you leave you car with the keys in the insurance does not pay out even if it is only left for a minute while opening a gate or garage door etc.
If people choose to wreck their cars then they should accept responibilty for their actions.
Driving through flood water - how deep can you go? - Screwloose
Cliff

If the car has been idled for a few minutes before entering the water, then the cat will be around 150-180C going in and 200-odd coming out. The stainless casing will certainly contract, but most good cats would stand it - at a wild guess, I'd expect a failure rate of under 1%.

A very hot cat [450C] or one of the many cheap and very nasty ones, now getting everywhere, might be a different story.
Driving through flood water - how deep can you go? - ForumNeedsModerating
There are lots of mini-floods in my neck of the (rural welsh) woods. I regularly ford up to the engine undertray/ just below wheel mid-line (Merc C-class)- if you didn't around here you'd never get anywhere. I do about 5mph & generally know how deep it's going to get before I start, since I regularly use the same (flooded) roads.
The under parts of my car are pretty well 'undertrayed' , so I don't mind a good splash through anything less than whole road-width floods - in fact - younger passengers positively relish a good splash that sets the auto wipers off! (So do I actually!)
Driving through flood water - how deep can you go? - Chad.R
The kids love driving through water in the Landcruiser - anything less than a 1ft doesn't even get a second thought.

In our other car, a (1.3 petrol) Yaris, any more than 3-4 inches is a no-no.
Driving through flood water - how deep can you go? - Westpig
few years back drove mate's wife's Suzuki Jeep along a flooded country road where the river/stream had burst its' bank.....wasn't the wisest thing i've ever done

it was at night....and as we gently went forward (on tarmac) we were going against the flow of water...which promptly went right up over the lights and bonnet and started going either side of the windscreen

the depth wasn't that deep, but the flow made it seem so

i kept it revving at 6,000 revs and it didn't miss a beat, but wouldn't repeat that again, with the lights under water it was pitch black, so very difficult to reverse...had to unzip the roof to the rear to see by a bit of moonlight....stupid really
Driving through flood water - how deep can you go? - Sofa Spud
QUOTE>>>>If water gets drawn into the air intake, normally the air filter will prevent it reaching the engine.

But if it does get drawn through the filter and into the cylinders, being uncompressable in liquid form, the water will cause catastrophic damage like bent con rods. This does happen - I know of a case.
Driving through flood water - how deep can you go? - borasport20
QUOTE>>>>If water gets drawn into the air intake normally the air filter will prevent it
reaching the engine.

Just as a matter of interest, say you have a 2000cc engine running at 1000 rpm, what volume of fluid is that pumping through the engine, per second, per minute ?

tia

Driving through flood water - how deep can you go? - Screwloose
Just as a matter of interest say you have a 2000cc engine running at 1000
rpm what volume of fluid is that pumping through the engine per second per minute?


On a diesel, without making any deductions for relative efficiency, 1000 litres a minute of air - or half-a-cupful of water.

[Because after the first half-cupful of water, it likely won't be drawing in anything, ever, again.]

Driving through flood water - how deep can you go? - Sofa Spud
In the 70's I was working as a van driver. I was in a Bedford CF coming up to a ford across the road in a village. Now I was never a tearaway driver but, being about 19, I thought I'd go a bit faster than normal through the ford since the road was clear. But round the bend came an orange MGB GT with a smartly dressed woman at the wheel. She passed me just as I was at maximum splash and her drivers' window was wide open!

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