Why is there excessive exhaust gas without burning engine oil?

[DamianFitz]

Excessive exhaust gas without burning engine oil is most likely caused by excessive piston ring clearance, which produces waste gas. Valve stem seals do not cause this type of exhaust gas, and excessive valve guide clearance can also lead to this phenomenon, although such faults are rare. The main causes are still related to the piston and piston rings. The following are the reasons for the fault: 1. Wear of the engine piston rings: Severe wear of the engine piston rings and cylinder liners, piston top erosion or cylinder scoring. If the piston rings and cylinder liners are severely worn, or if there is piston top erosion or cylinder scoring, the seal between the piston rings and cylinder liners becomes loose. During the compression and expansion processes of the diesel engine, a large amount of compressed gas enters the crankcase through the tiny gaps between the piston rings and cylinder liners, leading to increased crankcase exhaust gas pressure. The main symptoms include severe exhaust gas from the breather, insufficient engine power, and possibly blue smoke. 2. Incorrect installation of engine piston rings: If the piston rings are installed incorrectly with all gaps aligned, even if the piston rings are not worn, a large amount of high-pressure gas during the compression and expansion processes will enter the crankcase, causing increased crankcase exhaust gas pressure.