While conducting a cylinder leakage test, bubbles are seen in the coolant in the radiator. Technician A says a failed exhaust valve is the cause. Technician B says a failed intake valve is the cause. Who is right?

In a cylinder leakage test, the presence of bubbles in the coolant within the radiator typically indicates a breach between the combustion chamber and the cooling system, often due to a head gasket failure or a crack in the cylinder head or block.

When considering the roles of the valves, a failed exhaust valve primarily allows exhaust gases to escape into the exhaust system rather than leaking into the cooling system. An intake valve failure would allow fuel and air mixture to enter the cylinder incorrectly, but it wouldn’t produce bubbles in the coolant either. Both scenarios described do not directly result in coolant contamination through bubbling.

Thus, since neither a failed intake valve nor a failed exhaust valve would explain the observed symptoms in the radiator, the conclusion is that neither technician is correct in attributing the bubbles in the coolant to valve failure.