🍋 Bad choices. We call them out.

What it is:

A low-frequency metallic tapping or knocking noise, especially when accelerating.

Why it happens:

• Bearings are designed to float on a microns-thin oil film.
• When debris scratches or gouges the bearing surface, the oil film breaks down.
• The crankshaft starts making direct metal-to-metal contact with the bearing.
• Each rotation produces a “tap” or “knock,” especially under load when forces are highest.
   

Think of it like this:

It’s the same sound you’d hear if a spinning shaft started hitting the sides of its housing because the cushion between them disappeared.

Why it happens:

• Bearings act like restrictions that oil pump pressure works against.
• When debris wears down the bearing material, the gap between the crankshaft and bearing widens.
• Oil escapes out the sides faster than the pump can maintain pressure.
• Result: overall system oil pressure drops, often triggering a dashboard warning.
   

Analogy:

Imagine trying to build water pressure in a hose when you’ve cut slits down its length — the pressure just can’t build.

Why it happens:

Once metal-to-metal contact begins:

• The crankshaft journals (the round surfaces it spins on) begin grinding against damaged bearings.
• The oil that should protect them is contaminated with metal shavings.
• This creates a vicious cycle:
  Debris → wear → more debris → more wear.

Eventually, the crankshaft journals become scored or warped — a death sentence for the engine.

Bottom line:

Once journal wear begins, the engine is on a countdown to catastrophic failure.

Why this occurs:

A crankshaft with a failing bearing:

• No longer rotates smoothly 
• Experiences slight “wobble” or drag
• Creates inconsistent rotational speed 

Engines rely on extremely precise crankshaft rotation to determine:

• When to fire spark plugs 
• When to inject fuel
• When the valves open/close 

If the crankshaft slows suddenly for even a fraction of a second:

• The computer detects irregular rotation 
• Cylinders fire at incorrect times
• Misfires occur under load
   

Translation:
A sick crankshaft throws the whole engine’s timing out of sync.

This is the catastrophic moment.

Why it happens:

As wear accelerates:

• Metal shavings contaminate the oil
• Bearing surfaces overheat
• The soft bearing metal melts or deforms
• The bearing grabs the crankshaft
• The crankshaft cannot rotat 

This is called bearing seizure, and it’s equivalent to throwing a wrench into a spinning fan.

When this happens:

It’s sudden, violent, and final — the engine stops instantly.

When the crankshaft locks, everything connected to it stops as well. 

That’s when the secondary failures occur: 

The crankshaft is the engine — it converts combustion into motion.

If it can’t rotate:

• Pistons can’t move
• The engine cannot fire
• Power output drops to zero instantly
   

This is why drivers often describe it as: “The truck just died.”

Turbochargers are driven by exhaust flow, which comes from combustion.

If the crankshaft stops:

• Combustion stops
• Exhaust flow drops to zero
• Turbocharger turbines coast to a halt
   

The vehicle loses all boost pressure immediately.

Many trucks/SUVs use hydraulic power steering pumps driven by the engine.

When the crankshaft stops:

• The steering pump stops
• Power assist disappears
• Steering becomes extremely heavy
   

This is dangerous at highway speed.

Many brake boosters rely on engine vacuum.

When the engine dies:

• Vacuum production stops
• The brake pedal becomes stiff
• Brake assist is reduced
   

This does not eliminate braking — but it makes braking MUCH harder.

 Combine:

• Power loss 
• No steering assist
• Reduced brake ass
• No turbo boost 
• No acceleration capability
   

…and the vehicle simply stalls in traffic or on the highway.

This is why NHTSA treats these bearing defects as major safety hazards — because the failure mode can cause a total loss of motive power without warning.