Advanced Diagnostics: B Scan Engine Inspection Service
The B Scan is the most comprehensive engine inspection available without tearing apart the engine. The B Probe, designed for both spark-ignited and diesel engines, gives a fast, convenient method to identify problems and perform repairs before the engine suffers severe damage or downtime.
How Does B Scan Work?
For a B Scan, the engine’s spark plug or injector is removed, and a specially designed probe (B Probe) is inserted into the opening. Next, 80 psi air pressure is blown into the cylinder and the leak rate is measured. Leakage of greater than 1X the cylinder bore, measured in standard cubic feet per minute (SCFM), is considered abnormal.
A vacuum is then induced by reversing the flow through the cylinder, lifting the piston and rod. A dial indicator measures the amount of piston travel and the dial indicator’s needle will experience a momentary pause when the weight of the connecting rod is first encountered. The amount of piston travel to this point is equal to wrist pin clearance. More vacuum is applied and the total lift achieved. Subtracting the total lift value from the wrist pin clearance value results in the rod bearing clearance. The engine’s OEM supplies acceptable clearance values for comparison.
An excessive leakage rate indicates anomalies with the rings, liner, valves, or head. Excessive or minimal clearance indicates rod, wrist pin, or busing problems. For some models, master rod clearances can also be measured. Once this information is recorded, we perform a complete borescope inspection of the cylinder, including pictures of all components. The time spent in each cylinder is approximately ten minutes, so in an average of two hours, we have performed a comprehensive top-end examination of the engine.
- Wrist Pin Bearing Clearance
- Rod Bearing Clearance
- Master Rod Bearing Clearance