There are several signs that may indicate a blown diesel engine, such as:

1. Loud knocking or banging noises coming from the engine: This can indicate that the pistons or connecting rods have failed and are striking the inside of the engine block.
2. Blue or white smoke from the exhaust: This can indicate that oil is being burned in the combustion chamber and can be caused by a failed piston or valve.
3. Loss of power and poor engine performance: This can indicate that the engine is not able to produce enough power due to a failure of one or more components.
4. Warning lights on the dashboard: Warning lights such as the check engine light or the low oil pressure light can indicate a problem with the engine.
5. Low compression: Low compression in one or more cylinders can indicate that the pistons, rings, or valves have failed.
6. Engine will not start or runs poorly: This can indicate a failure of one or more components, such as the fuel injectors, fuel pump, or air intake system.
7. Overheating: Engine running too hot, which can be caused by issues with the cooling system, low coolant levels, or a clogged radiator.
8. Vibration: Engine vibrating excessively, which can be caused by issues with the engine mount, drive belts, or imbalance in the rotating components.
9. Oil leaks: Oil leaks can occur due to worn or damaged seals, gaskets, or hoses, which can cause damage to the engine and lead to reduced oil pressure.
10. Excessive engine noise: Unusual noises such as knocking, ticking, or squealing can indicate problems with the engine and its components.

It’s important to note that these are signs that may indicate a blown diesel engine, but not a definitive diagnosis. It is best to consult with a qualified mechanic or technician for a proper diagnosis and repair. A diagnostic test, such as a compression test, can be used to confirm the failure of the engine. If the engine is found to be blown, it will likely need to be replaced or rebuilt.