Heavy, unceasing rain, overflowing watercourses and an often-inadequate network of surface water drains mean that highways can flood with alarming rapidity, creating hazardous driving conditions. Steve Banner assesses the risks for light commercial vehicles

Nobody would try to drive through a flooded road ideally, but some people may feel they have no choice but to make the attempt. They include emergency vehicles whose crews need to rescue stranded people whose lives may be in danger.

No matter what the justification, there is no denying that entering flood water poses a risk to both the vehicle and the individual at the wheel. Light commercials are especially vulnerable because they invariably lack the ground clearance enjoyed by bigger vehicles.

“Significant damage can be done to the internal components of an engine if water enters the air intake on a petrol or diesel vehicle,” warns Chris Woolsey, UK technical, quality and warranty director at global automotive giant Stellantis. “Admittedly an electric vehicle does not have such an air intake, but its components can be damaged by water nevertheless.” Stellantis embraces the Citroen, Peugeot, Vauxhall and Fiat Professional brands, all of which offer extensive light commercial ranges.

Says a Toyota spokesman: “Water can do major harm to an internal combustion engine if it is sucked in through the air intake and into the combustion chamber. You might get away with bent valves or conrods, but damage could also be done to the crank and pistons, depending on how much water is involved.

“As a consequence, you will need a new engine.”

Says Gary Digva, founder of onboard camera specialist Road Angel: “Water can cause irreversible and costly damage to multiple parts of a vehicle including the transmission, brakes, suspension and general electrical components.” If you are at the wheel of a van with a standard ride height, and the water rises above the middle of the tyres, or looks deeper than 100mm, then do not venture into it, he advises.

That is a view shared by recovery service the AA, which adds that the havoc wreaked by an ingress of water on a vehicle’s electrics can, among other things, cause an airbag to trigger for no discernible reason.

“It only takes an egg-cup full of water to be sucked into your engine to cause significant damage,” it warns. With many light vehicles, the air intake is low down at the front it adds, making it susceptible to water inflows.


How do you know if water has got into an engine?

Tell-tale signs include a fast cranking sound or whirring when you try to fire it up, as well as an abnormally strong smell of fuel, especially near the exhaust pipe, the AA says. The vehicle may not start at all, or start briefly, then stop again.

If you happen to operate 4x4 pick-up trucks such as Toyota’s Hilux, then you are less at risk of coming to grief, although the danger is not entirely eliminated. Because they are designed to tackle uneven terrain and cross the occasional stream, they have more ground clearance than a typical 4x2 van. That means they have more of a chance in deep water, although they are not invulnerable. Hilux, for example, boasts a wading depth of up to 700mm. It can be possible to increase a pick-up’s wading depth to closer to 800mm-850mm if you have the suspension jacked up and bigger wheels and tyres fitted.

Most 4x4 pick-ups can be equipped with a snorkel if the operator needs to travel down sections of highway that regularly end up under water. Costing around £400 to £500 plus VAT and fitting from a supplier such as Truckman, a snorkel in effect raises the truck’s air intake so it sits above the windscreen.

Most of those fitted are of the ram type, using a forward-facing duct into which air is rammed when the vehicle is in motion. Cyclone or vortex-type snorkels are also marketed, with tilted vanes inside the bowl-shaped head which cause the air to swirl around inside.

If you ask a workshop to install a snorkel, then make sure to opt for one that is specifically designed for the make of vehicle concerned, and is sized so that it can be mated to the body where the factory-fitted air intake sits. Universal ones are marketed but may not be easy to install, or all that effective once they are in position. Bear in mind that no snorkel will work if it is not properly sealed with a silicone sealant.


With a gross payload typically hovering at around 1.0 to 1.2 tonnes, there is a limit to how much weight in terms of equipment and emergency supplies a 4x4 pick-up can haul up a highway awash with muddy water.

If a lot more needs to be transported, and it is essential that it reaches its destination, then the answer may be to deploy one of Mercedes-Benz’s extraordinarily capable all-wheel-drive Unimogs. They can shift up to 7.5 tonnes, depending on the specifications, and are adept at coping with deep water. Grossing at up to 14.5t, a Unimog U5023 can be specified with a wading depth of up to 1,200mm as an option. A U5023 customer selecting this option was Cornwall Fire & Rescue Service.

Powered by a 227bhp 5.1-litre diesel which delivers 900Nm, its U5023 comes with the optional EAS automated manual version of the standard gearbox. To supplement its eight forward and six reverse gears, the service specified the working and crawler gear range, which provides another eight forward and reverse ratios.

Cornwall’s Unimog can avail itself of a number of different mission-specific pods which are lifted on and off using a Palfinger PK12502 SH crane mounted behind the cab.

Says Mark Salter, the service’s group manager, assets team: “Coupled with the Unimog’s impressive wading ability, the flood response pod enables us to recover residents who have become stranded in their homes after torrential downpours, as has happened two or three times in recent years.

“The disaster response pod contains heavy-duty equipment that might be used to rescue casualties in the event of anything from a building collapse to a plane crash, or an accident involving a heavy goods vehicle.”

Grossing at up to 7.0 tonnes, and with a payload capacity of up to 4.3 tonnes, IVECO’s 4x4 Daily, represents another mobility choice.


If you must get through flood water, then drive slowly and steadily, the AA advises, and do not create a bow wave. Let approaching vehicles pass first and remember that the water may contain hazardous debris – manhole covers that have broken loose, for example.

Once you emerge, test your brakes as soon as it is safe to do so, the AA adds; and if the water was deep, then ensure that whatever you were driving goes into a workshop at the first opportunity for a thorough safety inspection. The underside of the vehicle should be checked for damage caused by any underwater obstacles it may have encountered, and thoroughly steam-cleaned if it has been driven through diluted sewage.

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