You Turned the Key. Now What?
If you are reading this, you probably already tried to start your flooded car. Maybe you did not realise how deep the water was, or maybe the car seemed fine from the outside. Whatever the reason, what matters now is understanding what may have happened inside the engine and taking the right steps from this point forward to limit the damage and protect your insurance claim.
What Happens Mechanically: Hydrolock Explained
When your engine tries to start with water in the cylinders, a condition called hydrolock (hydraulic lock) occurs. Here is why it is so damaging: your engine works by compressing a mixture of air and fuel in each cylinder, then igniting it. Air and fuel compress easily because they are gases. Water does not compress. When the piston moves upward and hits a cylinder full of water, the force has to go somewhere. That force transfers through the connecting rod, which is the metal arm linking the piston to the crankshaft. The connecting rod bends, cracks, or snaps. In severe cases, the piston itself cracks, the cylinder wall fractures, or the crankshaft is damaged.
Assessing the Severity
What happened when you tried to start it? The answer tells you a lot about how severe the damage might be:
- Brief crank, then nothing: The starter motor engaged briefly but the engine would not turn over. This suggests water was present in the cylinders but the starter motor's limited torque prevented it from forcing the pistons through the water. Damage may be minimal. This is the best-case scenario among bad scenarios.
- Loud banging or knocking sounds followed by the engine stopping: This is the sound of connecting rods hitting water and bending. The damage is likely significant. At minimum, connecting rods are bent. The engine block and crankshaft may also be damaged. This is the most common hydrolock scenario.
- Engine seemed to start and run normally for a moment: This can happen when there is a small amount of water in the cylinders, not enough to cause immediate hydrolock but enough to cause internal scoring, bearing damage, and contamination. The engine may seem fine initially but develop problems over the following days or weeks. Do not assume everything is okay.
- Engine started and is running now: If the engine is currently running, turn it off immediately and do not restart it. Even if it sounds normal, water contamination of the oil, coolant, and fuel systems can cause progressive damage that destroys the engine over the next few hundred kilometres.
Can Your Engine Be Saved?
The answer depends on the severity of the hydrolock:
- Minor hydrolock (brief crank, no loud noises): There is a reasonable chance the engine can be saved. A specialist will remove the spark plugs or injectors, manually crank the engine to expel water, replace the oil and filters, and run a compression test. If all cylinders show healthy compression, the engine may be fine. Repair cost estimate: AED 1,500 to AED 5,000 for inspection, fluid replacement, and testing.
- Moderate hydrolock (knocking sounds, engine stopped): Connecting rods are likely bent. In some cases, only one or two rods are damaged and can be replaced. In others, the crankshaft or block is also damaged, requiring a full engine rebuild or replacement. Repair cost estimate: AED 5,000 to AED 25,000 depending on the make and model.
- Severe hydrolock (loud bang, visible metal debris in oil): The engine is almost certainly destroyed. Replacement is the only option. Cost estimate: AED 15,000 to AED 60,000+ for a new or remanufactured engine installed, with premium European brands at the top of that range.
Insurance Implications
This is the part that worries most people, and rightly so. Insurance companies can partially or fully deny claims if they determine that starting the engine caused or worsened the damage. The logic is straightforward: if the engine had water in it and you tried to start it, the hydrolock damage was caused by your action, not by the flood itself. Some insurers will still cover the claim but reduce the payout. Others may deny the engine claim entirely while still covering other flood damage (interior, electrics, etc.).
Being honest with your insurer is important. If you started the engine, tell them. Do not try to hide it because a forensic inspection of a hydrolocked engine will reveal whether the engine was cranked after water ingestion. Lying about it can void your entire policy, not just this claim.
What to Do Right Now
Follow these steps immediately:
- Stop: If the engine is running, turn it off. Do not restart it for any reason.
- Disconnect the battery: If you are comfortable doing so, disconnect the negative terminal to prevent any accidental electrical activation.
- Document: Take photos and videos of the vehicle, the water level marks, and the engine bay. Record any unusual sounds or smoke you noticed when you tried to start it. Write down exactly what happened while the memory is fresh.
- Call your insurer: Report the incident honestly. Tell them the vehicle was flooded and that you attempted to start the engine. Ask for a claim reference number.
- Arrange a flatbed tow: The vehicle must be transported on a flatbed to a specialist for inspection. Do not tow it with the wheels on the ground.
- Get a professional inspection: A flood damage specialist will assess the engine damage and provide a written report. This report is essential for your insurance claim. Visit our inspection services page to arrange an assessment.
Moving Forward
Starting a flooded engine is a costly mistake, but it is not always the end of the road. Minor hydrolock can often be resolved, and even when the engine needs replacement, the rest of the vehicle may still be worth saving. The key is to stop making the situation worse, get professional help immediately, and be honest with your insurer. Use our free flood damage checker to get an initial assessment of your situation.