Intake Valves Stuck Closed:
* No combustion: The most immediate consequence is a complete lack of air intake. Without air, fuel cannot combust, leading to a complete loss of power and potentially damage to the piston and cylinder walls. The cylinder will likely experience a vacuum condition.
* Piston damage: The vacuum in the cylinder can cause the piston to be pulled downwards too forcefully, leading to bent connecting rods, cracked pistons, or damage to the crankshaft.
* Hydrostatic lock: If there's any liquid (fuel, coolant, or even condensation) in the cylinder, the piston can't compress it, leading to catastrophic damage as the engine tries to turn over. This is a particularly severe risk for the engine.
Exhaust Valves Stuck Closed:
* Excessive cylinder pressure: The exhaust gases have nowhere to escape. The pressure buildup during combustion will be significantly higher than normal. This drastically increases stress on all the engine's components.
* Blown head gasket: The immense pressure can easily blow the head gasket, leading to coolant leakage, oil contamination, and compression loss.
* Cracked cylinder head or block: The extreme pressure can crack the cylinder head or even the engine block itself.
* Piston ring damage: Excessive pressure can damage piston rings, leading to blow-by (leakage of combustion gases past the piston rings).
* Bent connecting rods: The extreme pressure forces exerted on the piston can easily bend or break the connecting rods.
Both Intake and Exhaust Valves Stuck Closed:
This scenario combines the problems described above, resulting in a much more severe outcome. The catastrophic failure is almost guaranteed. The engine would likely seize completely due to the combined effects of hydrostatic lock and excessive cylinder pressure.
In short: Failure to actuate either the intake or exhaust valves in a diesel engine will lead to significant and likely irreparable damage. The longer the engine runs in this condition, the more extensive and costly the repairs will be. The engine may be beyond economic repair.
