PISTON-LOAD 1S3795 - Caterpillar

Analyzing the Results
The value for the blowby for each cylinder is obtained by subtracting the stabilized reading taken during each cut out cylinder from the reference value. The reference value is taken just before each cylinder is cut out. When repowering the injector the crankcase pressure should return to approximately the same stabilized value, duplicating the same change in blowby.Example Analysis
The example in Table 2 only uses four cylinders. For an actual test, values for all of the cylinders are used.
Table 2
Cylinder 1     Reference Value     8.32 in H2O    
Measured Value by cutting injector 1 7.52 in H2O    
Measured Value when repowering injector 1 8.41 in H2O    
Cylinder 8     Reference Value     8.52 in H2O    
Measured Value by cutting injector 8 8.63 in H2O    
Measured Value when repowering injector 8 8.46 in H2O    
Cylinder 13     Reference Value     8.22 in H2O    
Measured Value by cutting injector 13 8.12 in H2O    
Measured Value when repowering injector 13 8.18 in H2O    
Cylinder 16     Reference Value     8.89 in H2O    
Measured Value by cutting injector 16 7.89 in H2O    
Measured Value when repowering injector 16 8.79 in H2O    
Table 3
Cylinder 1 blowby contribution     8.32 - 7.52 = 0.80 in H2O    
8.41 - 7.52 = 0.89 in H2O Cylinder 1 has excessive blowby or a failed top ring.
Table 4
Cylinder 8 blowby contribution     8.52 - 8.63 = -0.11 in H2O    
8.46- 8.63 = -0.17 in H2O Cylinder 8 shows an increase in crankcase pressure. This cylinder is fine. The increase in blowby is caused by the transfer of load and increased injector duration to other powered cylinders.
Table 5
Cylinder 13 blowby contribution     8.22 - 8.12 = 0.10 in H2O    
8.18 - 8.12 = 0.06 in H2O Cylinder 13 shows only a slight drop in crankcase pressure. This cylinder is fine.
Table 6
Cylinder 16 blowby contribution     8.89 - 7.89 = 1.00 in H2O    
8.79 - 7.89 = 0.90 in H2O Cylinder 16 has excessive blowby or a failed top piston ring.Recommendations for Inspection
When suspect cylinders are found, perform the leak test in Special Instruction, REHS7138.
Illustration 6 g03316761
(1) Exhaust side plug (2) Valve cover holeAlternatively, cylinders can also be inspected with a borescope through the plug on the exhaust side of the cylinder head. Alternatively, the borescope can also be used through the valve cover hole with the respective valves open.If necessary, visually compare the suspect cylinder/s to a cylinder that tested ok. Evaluation Worksheet
Table 7
Date
    Unit
    Engine hours
   
Serial number
   
Coolant temperature (°C)
    rpm
   
Reference value for the whole engine (in - H2O)    
Oil Filter Differential Pressure at 1800 Rpm (170°F+ Coolant)