Bendix Air Compressor Inspection Of Parts

Cylinder Head Body

Inspect the cylinder head for cracks and obvious physical damage. Pay particular attention to the area around coolant ports for cracks. Check for stripped or damaged threads. Apply shop air pressure to one of the coolant ports with all others plugged, and check for leakage by applying a soap solution to the exterior of the body. If leakage is detected, replace the head.

End Covers

Check for cracks, stripped oil port threads and external damage; and if noted, replace the end cover. If the crankshaft main bearings are installed in the end cover, check for excessive wear and flat spots and replace the end cover if necessary.


Check all crankcase surfaces for cracks and damage. Pay particular attention to cooling fins. On compressors where ball bearing main bearings are used the difference between the O.D. of the outer race and the I.D. of the crankcase hole should be 0.000 to 0.038 mm (.0000 to .0015 in) loose. This is to maintain the correct press fit. The crankcase must be replaced if the fit is too loose.

On compressors fitted with precision, sleeve main bearings the difference between the O.D. of the crankshaft journal and the main bearing I.D. must not exceed 0.102 mm (.0040 in), or the end cover and main bearing must be replaced.

The cylinder bore should be checked with inside micrometers or calipers. Cylinder bores which are scored or out of round by more than 0.0123 mm (.0005 in) or tapered more than 0.0123 mm (.0005 in) should be rebored or honed oversize. Oversized pistons and piston rings are available in 0.25 mm (.010 in), 0.50 mm (.020 in) and 0.75 mm (.030 in) oversizes. The cylinder bore must be smooth, straight, and round.


Check the piston for scores, cracks, or enlarged ring grooves; replace the piston if any of these conditions are found. Measure the diameter of the top of the piston and the top two ring lands. [Compare to cylinder bore and piston diameters to be sure the diametrical clearance is between 0.325 mm (.0128 in) minimum and 0.500 mm (.0177 in) maximum].

Check the fit of the wrist pin to the piston. The wrist pin should be a light press fit in the piston. This clearance should not exceed 0.015 mm (.0006 in). If the wrist pin is a loose fit, the piston and pin assembly should be replaced. Check the fit of the wrist pin in the connecting rod by rocking the piston. Clearance for connecting rod wrist pin is 0.023 mm (.0009 in) max. Replace the connecting rod if excessive clearance is found. NOTE: Wrist pin bushing replacement is not recommended for those connecting rods which incorporate them.

Check the fit of the piston rings in the piston ring grooves. Check the ring gap with the rings installed in the cylinder bores. Refer to Figure 10 for correct gap and groove clearances.


Check the crankshaft threads, keyways, tapered ends and all machined and ground surfaces for wear, scores, or damage. Standard crankshaft connecting rod journals are between 31.750 mm (1.2500 in) and 31.725 mm (1.2490 in) in diameter. If the crankshaft journals are excessively scored or worn or out of round, the crankshaft must be replace. Main bearing journals must be maintained so the ball bearings are a snug fit or so that no more than 0.102 mm (.004 in) clearance exists between the precision sleeve main bearing and the main bearing journals on the crankshaft. In crankshafts fitted with oil seal rings, the oil seal ring groove or grooves must not be worn. The ring groove walls must have a good finish and they must be square. Using a wire or similar device, check to be sure the oil passages are open through the crankshaft.

Connecting Rods

The BX-2150 connecting rod does not incorporate replaceable crankshaft journal bearing inserts and must be replaced if excessively worn. Clearance between the crankshaft journal and the connecting rod bearing must not be less than 0.025 mm (.0010 in) or more than 0.064 mm (.0025 in).

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