YOKE AS 8Y6652 - Caterpillar

Excessive exhaust pressure will cause high exhaust temperatures. This high exhaust temperature can damage the substrate coating for the catalytic converter. Check the exhaust pressure in order to confirm the proper design of the exhaust system.The following factors can cause catalyst plugging:
Debris released into the catalyst from initial engine start-up
Deposits on the substrate from carbon fouling
Powdery gray/white ash caused by use of incorrect engine oil
Debris released into the catalyst from engine misfire and/or backfireExhaust pressure is measured as the engine is operating at rated speed and full load conditions. Use either a water manometer or a mechanical gauge to measure the exhaust pressure.The total exhaust pressure is measured from the test port at the inlet housing of the convertor. The total exhaust pressure is the pressure between the engine exhaust manifold and the converter.The total exhaust pressure for turbocharged engines ... 6.75 kPa (0.98 psi)The total exhaust pressure for naturally aspirated engines ... 3 kPa (0.44 psi)Check the exhaust pressure at the outlet in order to calculate the pressure differential across the convertor. The differential pressure will provide information about plugging of the catalyst. The pressure after the catalytic convertor is measured from the test port at the outlet housing of the convertor. Maximum differential pressure across the catalytic converter for turbocharged engines ... 2.02 kPa (0.29 psi)Maximum differential pressure across the catalytic converter for naturally aspirated engines ... 0.90 kPa (0.13 psi)If a problem with the catalytic converter is suspected, refer to the information in the following stories to identify the problem:Reference: Systems Operation, "Catalytic Convertor"Reference: Testing and Adjusting, "Catalytic Convertor Performance - Test"Reference: Testing and Adjusting, "Catalytic Convertor Substrate - Inspect"