Identification of Parts Failures

"Scuffing and scoring (adhesive wear) is caused by too much heat. When two metal parts rub and the heat builds up to the welding point, a small deposit or "hot spot" of metal is pulled out and deposited on the cooler surface.

"Scuffing leaves discolored areas on the surface of rings, pistons and cylinder walls.

"Scuffing starts as tiny surface disturbances. If they are not removed, scuffing spreads and becomes noticeable and more severe. It is then called scoring. Any engine condition which heats rubbing parts to the welding point, or which prevents the transfer of heat from these surfaces, influences scuffing.

"The following are possible causes of scuffing and scoring:

* Improper warm-up 
* Lubricating system not functioning 
* Cooling system plugged 
* Combustion knock and preignition 
* Lugging or overloading 
* Misaligned connecting rod

"Occasionally an unusual wear pattern results from a misaligned connecting rod. Contact with cylinder wall shows on the bottom of the skirt at left, and at the ring lands on the right (arrows). There is also a diagonal wear pattern extending across the skirt of the piston. This uneven wear is due to a bent or twisted connecting rod or shaft. When connecting rods are misaligned, rings do not have proper contact with cylinder wall, pistons wear rapidly and unevenly, oil consumption is excessive and the engine is prone to scuff or score. Always check rod alignment.

PISTONS, RINGS, CYLINDER LINERS AND GASKETS 
Introduction 
Identifying Piston Failures in Gasoline Engines
Detonation 
Preignition 
Scuffing and Scoring 
Corrosive Wear 
Physical Damage to Pistons 
Identifying Piston Failures in Diesel Engines Cracking 
Piston Breakage 
Wear 
Scuffing and Seizure 
Erosion 
Identifying Piston Ring Failures 
Wear 
Chipping 
Scuffing and Scoring 
Breakage 
Sticking 
Identifying Cylinder Liner Failures 
Cracking 
Chemical Attack 
Cavitation 
Wear 
Scratching 
Blown Head Gasket

JOURNAL BEARINGS 
Introduction 
Journal Bearings 
Dirt 
Lack of Lubrication 
Improper Assembly 
Misalignment 
Overloading 
Corrosion 
Electric current

VALVE GEAR TRAIN 
Introduction 
Identifying Valve Failures 
Distortion of Valve Seat 
Deposits on Valve 
Identifying Valve Failures 
Too Little Tappet Clearance 
Burned Valve 
Erosion of Valves 
Heat Fatigue 
Pitting Breaks 
Wear 
Identifying Rocker Arm Failures 
Identifying Push Rod Failures 
Bent Push Rod 
Identifying Valve Tappet Failures

TURBOCHARGERS 
Introduction 
Wheels and Impellers 
Foreign Material 
Sludge Build Up 
Contact Damage 
Abrasion-Erosion 
Shafts 
Oil Starvation 
Contaminated Oil 
Journal Bearings 
Oil Starvation 
Contaminated Oil 
Unbalanced Rotating Assembly 
Thrust Bearings 
Oil Starvation 
Contaminated Oil Housings

GEARS 
Introduction 
Gear Terminology 
General Category of Failures 
Wear Pitting, Spalling, and Case Crushing
Fatigue Impact 
Rippling, Ridging, and Cold Flow 
Combined Effects 
Ring Gear Teeth 
Ring Gear and Drive Pinion 
Drive Pinions 
Differential Side Gears and Pinions 
Differential 
Spider Arms and Side Pinions 
Rear Axle 
Differential Side Gears 
Transmission Helical Gear 
Transmission Splined Mainshaft 
Transmission Countershaft 
Transmission Mainshaft Second Speed Gear
Transmission Mainshaft Overdrive Gear
Transmission Countershaft Gear 
Bumps, Burrs and Swells on Operating Transmission 
Gear Teeth 
Appearance of Failure

SHAFTS, AXLES, SPINDLES, AND UNIVERSAL JOINTS 
Introduction 
General Category of Failures 
Overload Failure 
Fatigue Failure 
Torsional Fatigue 
Severe Service Frettage and Scoring 
Combined Fatigue Failures 
Impact Failures 
Improper Use 
Specific Category of Failures 
Crankshaft 
Pump Shafts 
Transmission Shafts 
Spindles 
Universal Joints 
Lack of Lubrication 
End Galling 
Brinelling 
Slip Spline Galling 
Fatigue 
Broken Journal

HYDROSTATIC TRANSMISSIONS
Introduction 
Heavy Duty Hydrostatic Systems
Thrust Plate or Fixed Swashplates 
Smearing or Galling 
Scoring 
Piston/Slipper Assembly 
Scoring 
Damaged Slipper 
Rolled 
Contaminated Slipper 
Smearing or Galling 
Discoloration 
Piston Filler Separation 
Slipper Separation 
Slipper Retainer Discoloration 
Scoring 
Low System Charge Pressure 
Ball Guides 
Scoring 
Worn Cylinder Block 
Pulled Bushing 
Fracture 
Bearing Plates 
Smearing-Outer Edge 
Erosion 
Grooved 
Total Smearing 
Discoloration and Smearing 
Discoloration 
Cavitation 
Bi-Metal Bearing Plates
Total Smearing 
Cavitation 
Metal Separation 
Valve Plate Contamination 
Smearing 
Grooving 
Shaft Seal 
Grooving 
Scoring 
Fracture
Charge Pump Assembly 
Fractured Input Flange 
Displacement Control Valve 
Broken Spring 
Broken Control Shaft 
Servo Sleeve and Piston 
Fracture 
Scoring 
Shafts 
Worn Spline 
Fractured Input Taper 
Worn Spline 
Light Duty Hydrostatic Systems 
Stuck Piston 
Valve Plate/Charge Pump Housing

ANTI-FRICTION BEARINGS 
Introduction 
Anti-Friction Bearings 
Contamination 
Improper Lubrication 
Improper Installation 
Careless Handling 
Misalignment 
Severe Service 
Vibration 
Electric Current

BELTS AND CHAINS 
Introduction 
V-Belts 
Cracking 
Rupture 
Tear 
Burn 
Gouges 
Wear 
Internal Cord Failure 
Cuts 
Peeling, Fraying, Chewing 
Banded V-Belts 
V-Belts 
Ridging Outside of Sheave Groove 
Bottoms of Belts Cracking 
Top of Band Frayed, or Damaged Band
Separating From Belts 
Holes or Blisters in Tie Band 
Special V-Belts 
Frayed Edges 
Narrow Wear in One Section 
Drive Belt Disintegration 
Drive Belt with Sheared Cogs 
Flat Belts 
Flat Belt Tears 
Flat Belt Burn 
Chains 
Wear of Chains and Chain Parts 
Fracture of Chains and Chain Parts 
Corrosion of Chains and Chain Parts

TRACKS AND TIRES 
Tracks 
Links 
Pins and Bushings 
Sprockets 
Rollers 
Special Tracks 
Cable and Edge Damage 
Obstruction and Impact Damage 
Face Damage 
Lug Damage
Track Tension Damage 
Tires 
Fabric Breaks 
Rubber Checks 
Wear 
Tread Wiping 
Tread and Sidewall Cuts

MISCELLANEOUS FAILURES 
Introduction 
Pump Rotors 
Pump Impellers 
Disk Blades 
Spark Plugs 
Oil Test Kits
0-Rings 
Intercooler Brace 
Fasteners 
Failures During Assembly 
Galling 
Bolt Yield and Tensile Failure 
Nut/Cap Screw Thread Failure 
Nut Dilation 
Galling 
Failures During Use or After Assembly 
Fatigue Failure 
Loss of Cap Screw Torque After Assembly