Free advice from Haynes’ Technical Editor Driving through water: ⬆️ or ⛔️? | | | As someone who has lived on the edge of the Somerset Levels for many years, I have some wisdom to dispense concerning driving through water, now that our typical British weather is returning after the recent cold spell. | | | The damage water can do to your vehicle
The best advice about driving through a flooded section of road is… don’t. It’s extremely dangerous and it does your car no good at all. The roads often have ditches running parallel to them, and if the water’s deep enough, it’s not possible to tell where the road stops and the ditches start. And you do not want to drive into a flooded ditch.
As well as the immediate danger, flood water will wash any lubrication from the suspension joints and bearings. It can remove the grease between the brake pads, the calipers and the CV joints if the boots are damaged. And if it gets into the transmission bell housing, it can cause the clutch to fail. | | Apart from being swept away by the flood waters, the main danger of driving through them is ingesting water into the engine. Fluids don’t really compress, so if water gets into the combustion chamber, the pistons will hit the water and something will break. It's called hydraulic locking, or hydrolocking, and it could be the piston, connecting rod, crankshaft, cylinder head, etc. Basically, the engine will be wrecked.
If you absolutely have to drive through that flood, here are a couple of points to bear in mind: - Keep the car in a low gear (first, preferably) and go slow to keep the bow wave as small as possible. The engine air intake is usually just below the bonnet line.
- Unless you can see that the water is shallower on one side, try to stick to the middle of the road. The camber often makes the water deepest at the edges. Obviously, you'll have to rely on there being no oncoming traffic, or hope that vehicles on the other side of the flood will wait for you to come through. If they don't, their bow wave could well swamp you.
| | | Technical Editor, Martynn Randall has been with Haynes for 27 years and has written more than 60 Haynes Manuals. | | | | | | |  |
