* Frozen Water: If water froze in the engine block, the expansion of ice could exert immense pressure, potentially cracking the oil pan or the related metal plate (likely the oil pan baffle or windage tray). This is especially likely if you didn't properly address the water intrusion issue before extremely cold temperatures.
* Excessive Pressure Build-up from a Blocked/Failing Oil Gallery: A blockage in an oil passage within the engine could cause a pressure buildup that eventually ruptures the weakest point – potentially your oil pan. This is less likely to cause the "exploded" appearance unless combined with other factors.
* Engine Failure Related to Water Ingress: Water in the engine can cause catastrophic damage, leading to bent connecting rods, piston damage, or other internal failures that can then create pressure that leads to the oil pan failure. This is a more plausible scenario given the descriptive word "exploded". The pressure from a destroyed engine component could literally blow out parts of the oil pan.
* External Force (Less Likely): While less probable, a significant impact to the undercarriage could theoretically damage the oil pan. This is less likely to create the "exploded" effect unless accompanied by other damage.
Why water ingress is a factor: Water in the engine cylinder can cause hydrolock (the piston cannot compress the incompressible water), bending a connecting rod, or causing other critical engine damage. This damage can then generate the pressure needed to rupture the oil pan.
What you should do:
1. Don't try to start the engine. Further damage is highly likely if you do.
2. Have it towed to a qualified mechanic. They can diagnose the root cause of the damage, which is crucial for determining the extent of repairs needed (a new oil pan might be the least of your problems).
3. Describe the "exploded" damage as clearly as possible to the mechanic. Pictures would be invaluable.
In short, water in the engine is a serious problem and likely played a significant role in this catastrophic failure. The "exploded" appearance points towards a much more severe internal engine failure likely caused by the water damage, which then led to the oil pan damage as a secondary effect. A proper inspection is absolutely necessary to determine the full extent of the damage and the best course of action.
