B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 001-006   Bearings, Main

The engine has seven main bearings. The lower bearing shells are all the same. All of the upper bearing shells are also the same with the exception of the journal adjacent to the rear one. The next-to-last journal is fitted with a flanged upper bearing shell and is referred to as thee thrust bearing. The flanges control the end thrust of the crankshaft.

The upper bearings have three holes in them. The middle hole receives lubricating oil from the main oil rifle. One of the adjacent holes is aligned with a drilling in the camshaft journal and serves as an orifice for lubrication flow to the journal. The other adjacent hole supplies lubricating oil for piston cooling. The hole does not align perfectly with the cooling nozzle. The hole is offset to keep it away from the highly loaded bearing area.

NOTE: Oversize main bearings are available for reground crankshafts. These are available from your Authorized Cummins Repair Location.

Improper maintenance of the lubricating system is the primary cause of reduced main bearing life.

WARNING  Some state and federal agencies have determined that used engine oil can be carcinogenic and cause reproductive toxicity. Avoid inhalation of vapors, ingestion, and prolonged contact with used engine oil. If not reused, dispose of in accordance with local environmental regulations

WARNING  To avoid personal injury, avoid direct contact of hot oil with your skin.

Drain the lubricating oil. Refer to Procedure 007-025.

Remove the lubricating oil pan and gasket. Refer to Procedure 007-025.

NOTE: Before removing the main bearing caps, make certain that the caps are clearly marked for their location on the lubricating oil cooler side of the main bearing cap.

Mark the bearing shell with the letter L (lower) and the journal number from which it was removed.

Perform an inspection of the main bearings and crankshaft journals. Remove the number 2 and 3 caps, and check the crankshaft journals for signs of overheating, deep scratches, or other damage. If there is no damage, there is no need to pull the other main bearing caps at this time.

Remove all main bearing caps except for numbers 1 and 7.

Pin, Part Number 3823818

Use a pin to roll out the upper bearings from between the crankshaft and cylinder block.

To make a pin, grind a 6-mm [0.24-in] capscrew to the dimensions shown, or use pin, Part Number 3823818.

Install the pin into the lubricating oil hole in the crankshaft. Rotate the crankshaft so the pin pushes against the end of the main bearing opposite the tang. Remove the main bearing.

Follow this procedure to remove the other main bearings.

CAUTION  Do not use a scraper or a wire brush. The bearings can be damaged.

WARNING  When using solvents, acids, or alkaline materials for cleaning, follow the manufacturer’s recommendations for use. Wear goggles and protective clothing to reduce the possibility of personal injury.

WARNING  Wear appropriate eye and face protection when using compressed air. Flying debris and dirt can cause personal injury.

NOTE: Make sure the bearings are marked for location. The bearings must be installed in their original location if used again.

Use solvent and a soft bristle brush to clean bearings.

Dry with compressed air.

Inspect all main bearing caps and main bearing crankshaft journals for dents, cracks, deep scoring, overheating, and other damage.

Inspect the crankshaft journals for deep scratches, indications of overheating, and other damage.

NOTE: If the crankshaft journals or main caps are damaged, the engine will need to be removed to complete the overhaul.

Determine the size of the main bearing removed, and obtain the same size for installation.

Refer to Procedure 001-016 for measurement specifications.

Measure the installed main bearing bore diameter.

A damaged, worn, or missing thrust bearing flange on the upper main bearing shell can be detected by measuring the end play of the crankshaft. Excessive wear will increase the end play.

CAUTION  Do not lubricate the side that is against the cylinder block. Engine damage can occur.

Apply a coat of clean lubricating engine oil to the new upper main bearings.

NOTE: Used bearings must be installed in their original location.

Position the new main bearing on the crankshaft, and install as far as possible by hand.

Pin, Part Number 3823818

Using the pin, Part Number 3823818, and rotation of the crankshaft, finish pushing the main bearing in slowly, being sure it is aligned with the cylinder block. Make sure the tang on the main bearing sets into the notch.

Make sure the pin does not slide under the bearing.

Install the lower main bearings into the main bearing caps. Apply a coat of clean lubricating engine oil to the inside of the main bearings.

NOTE: Do not lubricate the back of the bearing shell.

CAUTION  Make sure the caps are correctly installed with the number toward the oil cooler side of the engine. Failure to do so can result in engine damage.

23 mm

Install a main bearing cap after each upper main bearing is installed to keep the main bearing in place while the other uppers are installed.

Do not tighten to the final torque value at this time.

Use the same procedure to remove and install a rear main bearing cap, number 7.

CAUTION  Use care so the screwdriver does not damage the crankshaft or cylinder block.

NOTE: The front main, number 1, does not have a hole in the journal, so the pin can not be used to replace the bearing.

Use a flat-blade screwdriver. Gently bump the end of the bearing to loosen it from the cylinder block. Then, use finger pressure against the main bearing shell, and rotate the crankshaft to roll the main bearing out.

Lubricate and install the main bearing.

Use the screwdriver to push the main bearing into position as you rotate the crankshaft.

NOTE: The crankshaft must rotate freely.

Tighten the capscrews evenly and in sequence.

Check the main bearing installation and the size of the main bearings if the crankshaft does not rotate freely.

NOTE: The dimensions of the thrust bearing and crankshaft journal determine end play.

Measure the crankshaft end play.

Install the lubricating oil pan and gasket. Refer to Procedure 007-025.

Fill the engine with clean gas engine lubricating oil. Refer to Section 7 for the correct lubricating specifications.

Operate the engine at idle for 5 to 10 minutes. Check for loose parts and leaks.