Signs of engine damage and what to do when a car engine took in water in a flood

When a running engine takes in water (hydrolock), the sudden stop can bend connecting rods and damage internal components. This is because unlike air, water does not compress, destroying the metal around it. Here are the key signs of bent rods or internal damage:

1. Physical Symptoms During Engine Operation

• Knocking or Tapping Noise: A bent rod can cause a distinct knocking sound as it throws off the crankshaft balance.
• Rough or Uneven Idle or Misfiring: If a connecting rod is bent, the piston may not reach the correct height in the cylinder, causing poor compression and misfires.
• Loss of Power: Reduced compression in one or more cylinders leads to lower engine performance.
• Excessive Vibration: A damaged rod disrupts engine balance, causing noticeable vibrations.

2. Performance & Starting Issues

• Hard Starting or No Start: If the rods are severely bent, the engine may not crank properly, or it may seize completely.
• Check Engine Light (CEL): Misfires and compression issues can trigger error codes.
• Unusual Exhaust Smoke: If internal damage affects cylinder sealing, you might see blue (oil burning) or white (coolant burning) smoke.

3. Mechanical Inspection Signs

• Low Compression in One or More Cylinders: A compression test or leak-down test can reveal a problem.
• Visible Damage When Removing the Oil Pan: If the oil pan is removed, bent rods may be visibly deformed.
• Piston Height Variation: Measuring piston deck height (how far each piston reaches at top dead center) can reveal inconsistencies caused by a bent rod.

If you suspect water damage, a tear-down inspection is the best way to confirm bent rods or other internal damage before attempting repairs.

If an engine has taken in water during a flood and suffered bent connecting rods, it's essential to thoroughly inspect and potentially reface the engine block and cylinder head. Here’s why:

1. Inspect for Warping and Damage

• Cylinder Head Warping: Water ingestion can cause hydrostatic lock, which may lead to extreme forces on the engine components. The sudden stop can cause the cylinder head to warp, especially if the engine was running at high RPMs.
• Engine Block Warping or Cracks: The immense pressure generated by the water inside the cylinders can also lead to block distortion or cracking.

2. Reface (Resurface) If Needed

• If the cylinder head is warped, it should be refaced (milled) to restore a flat sealing surface.
• The engine block deck should be checked for flatness. If it’s warped, it might also need resurfacing.
• If there are deep gouges or cracks, resurfacing may not be enough, and the block or head may need replacement.

3. Additional Checks

• Check for piston and cylinder wall damage (scoring, cracks).
• Inspect main bearings and crankshaft for stress or damage.
• Replace head gaskets and rod bearings after repairs.

Final Recommendation

Before resurfacing, thoroughly inspect the engine components using a straightedge and feeler gauge. If warping exceeds manufacturer tolerances, resurfacing is necessary to ensure proper sealing and prevent further issues like compression loss or coolant leakage.