How to replace engine bearings

Knowing how to replace engine bearings can be a life saver for your engine.

Problems with engine bearings will usually result in some sort of knocking noise coming from your engine. The type of knocking noise that you hear will use the usually give you a good idea of which engine bearing is faulty or needs to be replaced.

1. Before disassembly, number each connecting rod and matching cap according to cylinder location and each main bearing cap as to its location in the block.

engine bearings
engine bearings

2. Loosen cap screws and lift main bearing caps until free from block. Use cap screws as a lever to free stubborn caps.

3. Bore gauges or inside micrometers are recommended for measuring housing bore dimensions. If not available, a good visual check should be made and any bores suspected of being incorrect should be checked carefully.

4. Use a micrometer to measure size, roundness and taper of the crankshaft.

5. One method to check the surface finish of a crankshaft is to rub a one cent coin several times across the surface of the shaft. If the shaft picks up copper from the coin, the shaft is too rough and must be reconditioned.

6. Any burrs found at the oil holes of the crankshaft must be removed, using a stone, file or scraper.

7. All oil passages must be clean. A brush and solvent should be used to clean these passages. Clean, dry, compressed air should also be used.

8. Select the correct part number and undersize bearing to suit the engine application.

9. Using a clean, lint-free cloth, wipe bearing back and bore surfaces. They must be clean and dry. Never put anything between the bearing back and bore surface.

10. Oil hole in block must line up with hole or slot in bearing to assure proper oil flow.

11. Rubber crankshaft seals must be installed with the sealing lip pointing toward inside of engine.

12. All bearing surfaces and seal lip must be lubricated with a good supply of lubricant.

13. Place the crankshaft gently and squarely onto the main bearings. Care should be exercised to prevent damage to the flange thrust surfaces. Main caps must be installed in proper position.

14. All threads must be clean and lightly lubricated to obtain accurate torque reading. Final tightening of all bolts and cap screws must be done with a torque wrench to proper specifications. Do not attempt to guess at torque tightening.

15. With a feeler gauge of proper thickness, check clearance between crankshaft thrust disc and bearing flange surface.

16. Before installing piston and rod assembly, cover rod bolt threads with suitable protectors to prevent nicking of crankshaft. A short piece of rubber hose is good for this purpose.

17. Place matching number cap on connecting rod. When torquing nuts, socket should be lifted slightly to clear cap ribs. Socket interference with cam rib can give a false torque reading.

18. After assembly, engine oiling system must be primed before starting engine to prevent dry start and premature damage to bearing surfaces.

Symptoms of Faulty Engine Bearings
Problems with engine bearings will usually result in some sort of knocking noise coming from your engine. The type of knocking noise that you hear will use the usually give you a good idea of which engine bearing is faulty or needs to be replaced.

  • Bad main bearing sounds. If you hear knocking sounds when you start your car that continue while the engine is running, and the sound is coupled with low oil pressure warnings, this is a good indicator that your engine has bad main bearings
  • Faulty rod bearing sounds. If the knocking noise sounds more akin to striking a piece of tin or aluminum and increases in intensity as you accelerate, the most likely culprit is a faulty rod bearing

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About Danny Bender 88 Articles
The premier engine troubleshooting resource site. DannysEnginePortal.com offers information on engine rebuilding, engine repair, machine operations, engine testing, and possible solutions.

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