How to Tell If You Have a Faulty Engine Bearing

February 21, 2012

Learn about the sounds that indicate faulty engine bearings, and the basics of engine bearing replacement.

Engine Maintenance

The engine bearing in your vehicle refers to either the engine's main bearings or the rod bearings. Engine bearings protect and support the connecting rod or crankshaft, enabling it to spin freely in the engine. When there are problems with engine bearings, the vehicle will demonstrate a few tell tale symptoms that must be addressed sooner rather than later.

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

Addressing Faulty Engine Bearing Issues
If your car displays either of the knocking symptoms discussed above, you should take it immediately to a qualified repair shop or mechanic to find out if the bearings need to be replaced. Replacing faulty main bearings will usually require replacing the crankshaft and all of the main bearings. A faulty rod bearing will usually require not only replacement of the bearings, but may require an engine rebuild as well.

Engine Bearing Replacement

When either rod bearings or main bearings in an engine fail, it is a good idea to replace all of the bearings in the set. It must be stated that this is a precision operation that most mechanics allow a machine shop with the proper tools to perform.

Tools and Materials

  • Wrenches
  • Sockets
  • Extensions
  • Ratchets
  • Screwdrivers
  • Pliers
  • A torque wrench
  • A gear puller set

Take Pictures and Disconnect
You should take pictures and label all your electrical and vacuum connections so that you get them right when you put everything back together. Once you have a few pictures and your connections all labeled, carefully disconnect all the electrical sensors and fittings and the vacuum fittings on your intake manifold. Then, remove the accelerator cable from the throttle plate. Take the inlet air tube off between the air cleaner and the manifold. Drain the radiator into a bucket and remove the upper radiator hose and the heater hoses.

Remove the Intake Manifold
Most intake manifolds on V8 engines will be secured with 16 bolts. All of these need to be removed. Work from the inside out to help prevent warpage. Set the intake manifold aside on some clean rags or newspaper.

Remove the Radiator and the Accessories
Remove the radiator, alternator, water pump, smog pump (if equipped) air conditioning compressor (don't disconnect the hoses) and the power steering pump (leave hoses attached) and set them aside. Set the engine to top dead center for cylinder number one to facilitate reassembly by rotating the crankshaft. Next, remove the timing gear set and set this aside. This is a good time to replace this item.

Remove the Camshaft
With the timing set removed, you will see two or three bolts that hold the camshaft in the block. Remove the bolts. You need to at least loosen the valve rockers to enable the removal of the lifters and pushrods. Before removing these, get a box and label it 1 through 8 and push the corresponding pushrod through by the correct number. Place the same lifter next to the pushrod it was paired with.

Important: Don't mix and match pushrods and lifters after use.

With all the lifters and pushrods removed, you can now remove the camshaft by carefully pulling it out the front of the engine.

Remove and Replace the Thrust Bearing
At the back of the engine you will see a thrust bearing retainer plate. This is secured to the block by either two or three bolts. Remove these bolts and the retainer plate and the thrust bearing will come out in your hands. Refer to a motor manual for proper torque wrench settings and replace with a new thrust bearing, reusing the retainer plate. Carefully reinsert the camshaft and reinstall the front retainer plate.

Everything you removed in the previous steps needs to be replaced now. First the pushrods and lifters. Then the cam gear and timing chain set and cover. The water pump comes next. Then install the accessories. Reinstall the radiator. Refer to your motor manual to find the torque sequence and wrench setting for the intake manifold bolts. Replace all the heater and radiator hoses, vacuum lines and electrical connections. Finally, reconnect the throttle cable to the throttle plate and attach the air intake tube.

With the proper tools and a motor manual, this engine bearing replacement procedure can normally be accomplished in an afternoon.

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