Visual Inspection of the Piston

3408 3408 GENERA GENERATOR TOR SET ENGINE ENGINE 78Z000 78Z00001 01 01143 01143 SEBP13 SEBP1379 79 -

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Product: GEN SET ENGINE Model: 3408 GEN SET ENGINE 78Z Configuration: 3408 GENERATOR SET ENGINE 78Z00001-01143

Reuse And Salvage Guidelines Visual Inspection of the Piston{1214} Media Number -SEBF8049-16

Publication Date -09/06/2006

Date Updated -12/06/2006

i02563276

Visual Inspection of the Piston{1214} SMCS - 1214 Engine:Commercial All 3044C (S/N: 3441-UP) Engine:Truck All Industrial Engine:with Turbochargers All Machine Engines: All Marine Engine:with Turbochargers All

Introduction This Reuse and Salvage Guideline contains the necessary information in order to allow a dealer to establish a parts reusability program. Reuse and salvage information enables Caterpillar Dealers Dealers and customers to benefit from cost reductions. Every effort has been made in order to provide the most current information that is known to Caterpillar. Continuing improvement and advancement of product design might have caused changes to your product which are not included in this publication. This Reuse and Salvage Salvage Guideline must be used with the latest technical technical information that is available from Caterpillar. For additional information about this guideline, consult Repair Process Engineering of the Marketing and Product Support Division at 1 (309) 675-5434.

Summary The engine reconditioning does not necessarily result in the installation of new pistons as part of the process of reconditioning. Pistons that meet the specifications in this guideline and other applicable guidelines can be expected to have the same performance in the same application until the next overhaul. Compare the pistons from this guideline with the pistons that are removed from the engine. This guideline gives specific types of wear. Some pistons cannot be salvaged. Reference this guideline before reusing a piston. The pistons that are considered unacceptable in this guideline should not be reused. Piston failure can be due to poor engine performance. Always correct the true cause of the original failure. Note: Salvaging pistons with extensive damage may not be practical due to labor costs.

References Reference Refer to Reuse and Salvage Guidelines, SEBF8059-12, "Procedure and Specifications to Clean and Measure Pistons". Reference Refer to Reuse and Salvage Guidelines, SEBF8051-05, "Inspection and Measuring Procedures for Piston Pins". Reference Refer to Contamination Control Guidelines, PEBJ0002, "Caterpillar Dealer Contamination Control Compliance Guide". Reference Refer to Special Instructions, SEHS8696, "Piston Cleaning Procedure".

Tooling and Equipment Table 1 Tooling and Equipment Part Number

Description

6V-7894

Microlite

6V-2196

Microscope

Refer to the latest version of the Service Manual, NENG2500, "Tools and Shop Products Guide" for any changes.

Nomenclature

3408 GENERATOR SET ENGINE 78Z00001-01143(SEBP1379 - 01)/Basic Search

Illustration 1

g01198372

The piston is from a 3114 engine or the piston is from a 3116 engine. (1) Crown (2) Crater (3) Ring Band (4) Ring Grooves (5) Ring Lands (6) Skirt (7) Pin Bore (8) Snap Ring Groove (9) Top Land (10) Cooling Jet Relief (11) Skirt Relief

Illustration 2

g01198447

The piston is from a 3114 engine or the piston is from a 3116 engine. (1) Crown

Page 2 of 53


Illustration 1

g01198372

The piston is from a 3114 engine or the piston is from a 3116 engine. (1) Crown (2) Crater (3) Ring Band (4) Ring Grooves (5) Ring Lands (6) Skirt (7) Pin Bore (8) Snap Ring Groove (9) Top Land (10) Cooling Jet Relief (11) Skirt Relief

Illustration 2

g01198447

The piston is from a 3114 engine or the piston is from a 3116 engine. (1) Crown

Page 2 of 53


(2) Crater (3) Ring Band (4) Ring Grooves (5) Ring Lands (6) Skirt (7) Pin Bore (8) Snap Ring Groove (9) Land (10) Skirt Relief

Illustration 3

g01198161

The piston is from a 3400 series engine of t he direct injection type with a double ring land. (1) Crown (2) Crater (3) Ring Band (4) Ring Grooves (5) Ring Lands (6) Skirt (7) Pin Bore (8) Snap Ring Groove (9) Top Land (10) Cooling Jet Relief (11) Skirt Relief

Page 3 of 53


Illustration 4

g01198198

The piston is from a 3400 series engine of the direct injection type with a single ring land. (1) Crown (2) Crater (3) Ring Band (4) Ring Grooves (5) Ring Lands (6) Skirt (7) Pin Bore (8) Snap Ring Groove (9) Top Land (10) Cooling Jet Relief (11) Skirt Relief

Illustration 5 The piston is from a 3500 series engine. (1) Crown (2) Crater (3) Ring Band (4) Ring Grooves (5) Ring Lands

g01198306

Page 4 of 53


(6) Skirt (7) Pin Bore (8) Snap Ring Groove (9) Top Land (10) Cooling Jet Relief (11) Skirt Relief

Illustration 6

g01198322

The piston from a typical precombustion chamber engine (1) Crown (2) Valve Pocket (3) Heat Plug (4) Crater (5) Ring Band (6) Top Ring Groove (7) Middle Ring Groove (8) Oil Ring Groove (9) Third Ring Land (10) Skirt (11) Pin Bore (12) Snap Ring Groove (13) Top Ring Land (14) Second Ring Land (15) Cooling Jet Relief (16) Skirt Relief

Page 5 of 53


Illustration 7

Page 6 of 53

g01198332

One-piece piston with a coating of graphite

Note: The piston and piston pin must be identified and marked with the cylinder number and orientation in reference to the front of the engine. Note: Do not mix and match pistons and piston pins from different cylinders. Ensure that the pistons and piston pins are oriented properly to the front of the engine upon reassembly.

NOTICE If the pistons and piston pins have been worn together, mixing the parts can possibly lead to pin rotation issues.

Illustration 8 Nomenclature for ring grooves (1) Ring Band (2) Top Ring Land (3) Second Ring Land (4) "J" Groove (5) Skirt

g01198333


Illustration 9

Page 7 of 53

g01198336

Nomenclature for ring grooves (1) Third Ring Land (2) Ring Band (3) Top Ring Land (4) Second Ring Land (5) "C" Groove (6) Skirt

General Procedures Follow the instructions in this guideline in order to determine if a piston is reusable. 1. Make a visual check of the overall condition of the piston. 2. Clean the piston thoroughly. 3. Reinspect the piston after cleaning for the following. {

Cracks

{

Scuffing

{

Holes

{

Additional visible damage

4. The following areas of the piston should be inspected before reusing. (a) Ring Band (b) Ring Groove (c) Ring Land (d) Skirt (e) Pin Bore (f) Snap Ring Groove 5. Measure the piston according to the specifications in the Reuse and Salvage Guidelines, SEBF8059, "Procedure and Specifications to Clean and Measure Pistons".

Initial Inspection Make a quick visual inspection of the piston before cleaning. If no obvious faults are found, clean the piston according to the instructions in the Reuse and Salvage Guidelines, SEBF8059, "Procedures to Clean and Inspect Pistons".

Visual Inspections Top of Piston


Page 8 of 53

Small cracks around the heat plug are normal. To measure these cracks, use a 34 gauge wire that has a d iameter of 0.15 mm (0.006 inch) as a gauge. A 6V-2196 Microscope and 6V-7894 Microlite can also be used.

Illustration 10

g01198512

Small cracks that are less than 0.15 mm (0.006 inch) wide around the heat plug.

Use the piston again.

Illustration 11

g01198517

The arrows show cracks that are wider than 0.15 mm (0.006 inch).

Do not use the piston again.

Illustration 12

g01198526

If necessary, use a 6V-2196 Microscope and 6V-7894 Microlite to measure the size of the cracks around the heat plug.


Illustration 13

Page 9 of 53

g01198531

View the cracks through the eyepiece of the 6V-2196 Microscope . This crack is wider than 0.15 mm (0.006 inch).


Illustration 14

g01198535

Large cracks connected to each other.


Illustration 15

g01198540

Crack (A) goes into the valve pocket. Cracks (A) and (B) are wider than 0.15 mm (0.006 inch).



Illustration 16

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g01198569

The crack goes across the area between the valve pockets.


Illustration 17

g01198570

Cracks in the crater that are not wider than 0. 15 mm (0.006 inch)


Illustration 18

g01198573

Crack (A) goes into the valve pocket. Callout (B) shows cracks that are connected to each other. If either type of crack is found, do not use the piston again.


Do not reuse the piston if the piston sh ows signs of contact with a valve or contact with valves. See Illustrations 19, 20, 21 and 22.


Illustration 19

Page 11 of 53

g01198626

The light marks are caused by contact with the valves. Find the cause of the contact with the valve and then inspect the piston for cracks.


Illustration 20

g01198629

The light marks are caused by contact with the valves. Correct the cause of the contact.


Illustration 21

g01198632

The heavy marks are caused by contact with the valves. Correct the cause of the contact.



Illustration 22

Page 12 of 53

g01198635

The light marks are caused by contact with the valves. No material has been embedded into the surface of the piston. Check for cracks in the ring band area and measure the pin bores before reusing.


Illustration 23

g01198642

Typical example of pitting


Illustration 24

g01198651

The light pitting on the piston crown and in the area of the valve pockets is acceptable.


The latest designs of direct injection pistons have a sharp edge at the edge of the crater bowl in order to ensure good engine performance for emissions and fuel economy. Fine cracks can begin at this sharp edge due to thermal fatigue and mechanical fatigue. Although some fine cracking may be normal, severe cracks can be a sign of severe engine load factor. The pistons with crater cracks that are less than 6.00 mm (0.236 inch) long may be reused. The piston can be reused if the cracks are on the edge of the crater rim of the piston. The cracks in the piston should not be within 30 degrees of the centerline of the piston pin bore.


Illustration 25

Page 13 of 53

g01198655

Cracks that are less than 6.00 mm (0.236 inch) long are allowed within the shaded area.

(1) The centerline of piston pin bore (A) 30 degrees (B) 6.00 mm (0.236 inch)

Illustration 26

g01198667

The cracks are in the crater area of a direct injection piston. Measure the length and angle of the crack in relation to the pin bore. Use the piston again if the crack is less than 6.00 mm (0.236 inch) wide and the crack is not within 30 degrees of the pin bore.

Illustration 27

g01198673

The crack in the piston is outside of the allowable area for cracks.



Illustration 28

Page 14 of 53

g01198681

Remove burrs or raised edges with a file or a small grinder.


Use the piston again after the raised edges are removed and the piston is cleaned and completely inspected.

Illustration 29

g01198686

Light damage to the edge of the piston crown.


Use the piston again after the raised areas have been cleaned. Use the piston after the areas have been completely inspected. Pistons that have cracks in the area of the valve pockets should not be reused. The material that is below the valve pocket of the piston sho uld not be removed. Do not remove any sharp edges or any other material that has been embedded in the piston that can be easily removed by h and.

Illustration 30 The damage is to the edge of the piston crown.

g01198701



Use the piston again after the raised areas are removed and the area of the ring land is checked carefully.

Illustration 31

g01198704

The damage is to the edge of the piston crown.


Use the piston again after the raised areas have been removed and the area of the ring land is checked carefully.

Illustration 32

g01198777

Arrow (A) shows a small chip on the top of the piston. Arrow (B) shows debris on top of the piston.


Use the piston again after the raised edges or debris is removed with a file.

Illustration 33

g01198780

The small holes (A) are caused by debris. Light pitting (B) in crater.

Page 15 of 53



Illustration 34

g01198781

There is light pitting in the area of the valve pocket.


Illustration 35

g01198785

Do not reuse any piston that has heavy pitting on the entire crown.


Illustration 36 The light amount of erosion that is allowable


g01198788

Page 16 of 53


Page 17 of 53

Illustration 37

g01198791

The piston displays the maximum amount of erosion that is allowable. Do not reuse a piston that is displaying the severity of erosion that is more than the amount that is shown in Illustration 37.


Illustration 38

g01198792

The piston has heavy erosion on the crown. Any piston that is displaying this severity of erosion anywhere on the crown should not be reused.


Illustration 39

g01198796

The close up photo of a piston with heavy erosion



Illustration 40

Page 18 of 53

g01198805

The heat plug is loose and uneven with the surface of the crater. If the plug requires tightening, do not reuse the piston.


Pitting of the Piston Crown

Illustration 41

g01198814

The piston crown is showing light pitting.


Illustration 42 The piston crown is showing light pitting.


g01198821


Illustration 43

Page 19 of 53

g01198965

The piston crown is showing numerous deep pits and distinct pits.


Fuel Erosion The piston has erosion in the area of the crater that is caused by fuel. The erosion of the piston that is caused by fuel is only a problem of appearance and the structural integrity of the piston is not affected. Use the photos that follow to determine if the piston can be reused.

Illustration 44

g01198972

The crater of the piston is showing light erosion that is caused by fuel.


Illustration 45

g01198977

The crater of the piston is showing light erosion that is caused by fuel.



Illustration 46

g01198982

The crater of the piston is showing numerous areas of erosion that is caused by fuel.


Do not use pistons that have more severe erosion than the piston that is shown.

Illustration 47

g01198986

The crater of the piston shows deep erosion that is caused by fuel.


Illustration 48

g01198989

The crater of the piston is showing six points of deep erosion that is caused by fuel.


Page 20 of 53


Illustration 49

g01198990

The crater of the piston is showing multiple points of deep erosion that is caused by fuel.


Top of the Ring Land

Illustration 50

g01199009

The piston shows normal carbon scratches. The scratches are common on pistons with offset pin bores.


Illustration 51 Example of light carbon scratches on the piston


g01199013

Page 21 of 53


Illustration 52

Page 22 of 53

g01199018

The piston is displaying heavy carbon scratches in the top ring land.


Illustration 53

g01199021

The piston has light carbon scratches in the top ring land.


Use the piston again after the raised areas are removed with a file and the piston is properly cleaned. Refer to the Reuse and Salvage Guidelines, SEBF8059, "Procedures and Specifications to Clean and Measure Pistons".

Illustration 54

g01199026

Deep scratches on the piston which have offset pin bores.




Page 23 of 53

Note: If an engine failure has caused a force against the piston, the piston must be visually inspected for cracks. Refer to Illustrations 55, 63, and 77.

Illustration 55

g01199027

A crack in the top land of the piston


Illustration 56

g01199028

Minor damage to the top lands of the piston



Illustration 57 Minor damage to the top land of the piston

g01199038


Page 24 of 53



Ring Band, Ring Grooves and Ring Land

Illustration 58

g01199084

The piston is showing separation of the ring band. Check below the ring band and above the ring band. The piston is not reusable if there is the slightest separation in the ring band.


Illustration 59

g01199093

The piston has had pieces that are broken out of the top land and the ring band.


Illustration 60 A chip in the oil control ring groove

g01199096


Page 25 of 53

Do not use the piston again. Note: The piston can be reused after a burr or a raised area is made smooth with a file.

Illustration 61

g01199148

Carbon in the ring grooves of the piston


Use the piston after the carbon deposits are removed. Refer to the Reuse and Salvage Guidelines, SEBF8059, "Procedures and Specifications to Clean and Measure Pistons".

Illustration 62

g01199152

Damage to the piston groove


Illustration 63

g01199157


Page 26 of 53

The crack is in the ring land of the piston.


Illustration 64

g01199167

The damage is to the ring land of the piston.


Illustration 65

g01199168

The damage is to the ring land of the piston. The piston is not reusable as the ring lands have been compressed. Filing the area smooth will not make this piston reusable.


Procedure to Inspect Skirt

Illustration 66

g01199171

An example of a piston with normal wear on the skirt. The area that is gray has many small scratches.


Page 27 of 53


Use the piston again after the scratches are removed by cleaning with glass beads. Refer to the Reuse and Salvage Guidelines, SEBF8059, "Procedures and Specifications to Clean and Measure Pistons".

Illustration 67

g01199282

A piston that has light scratches on the skirt


Use the piston again after the scratches are removed by cleaning with glass beads. Refer to the Reuse and Salvage Guidelines, SEBF8059, "Procedures and Specifications to Clean and Measure Pistons".

Illustration 68

g01199285

The piston skirt is from a 3500 series engine that has been cleaned per the guideline the Reuse and Salvage Guidelines, SEBF8059, "Procedures and Specifications to Clean and Measure Pistons". The piston skirt still has light scratches but there is no raised material.


Illustration 69

g01199295


Page 28 of 53

The piston is showing evidence of seizure. The piston has more damage that is suggested so the piston should not be reused.


Illustration 70

g01199297

The piston shows scuffing just below the bottom ring groove.


Use the piston again after the skirt has been cleaned and inspected. Refer to the Reuse and Salvage Guidelines, SEBF8059, "Procedures and Specifications to Clean and Measure Pistons".

Illustration 71

g01199299

The piston shows small shiny areas of particles or aluminum bearing material that have been embedded in the skirt.


Do not use the piston again unless the particles can be removed by cleaning with glass beads. Refer to the Reuse and Salvage Guidelines, SEBF8059, "Procedures and Specifications to Clean and Measure Pistons".


Illustration 72

Page 29 of 53

g01199304

The piston shows metal particles in the skirt. The piston has dark particles that are not aluminum so the piston should not be reused.


Illustration 73

g01199310

The piston is showing the maximum amount of damage to the skirt that is possible. A piston must have no raised material in order to be reused.


Illustration 74

g01199315

The piston displays wear due to lack of lubrication for a short period of time.


The piston can be reused if there is no raised material or embedded material in the skirt after being cleaned.

Illustration 75

g01199316

The piston is showing damage just below the ring groove. The piston has no cracks that are visible.



Page 30 of 53

Use the piston again after the raised material is removed with a file and the piston is clean. Refer to the Reuse and Salvage Guidelines, SEBF8059, "Procedures and Specifications to Clean and Measure Pistons".

Illustration 76

g01199329

A piston that has light damage to the bottom of the skirt



Illustration 77

g01199333

The piston is showing heavy damage to the skirt. A piston with cracks in any area of the skirt make the piston unusable.

Do not use the piston again. Note: Illustrations 78 and 79 are displaying a crack in the piston skirt of a C15 piston. The piston skirt that is shown in Illustration 78 and Illustration 79 is the same piston.

Illustration 78

g01243290


The C15 piston is showing damage to the piston skirt. There is a crack near the hole for the pin.


Illustration 79

g01243598

The location of the vertical line is at the transition line of the piston skirt.


Graphite Coated Pistons If a piston has severe scoring, material transfer, embedded material, or other obvious damage the piston should not be used again.

Illustration 80

g01199385


If the cover plates of the cooling gallery are found in a loose condition the piston should not be used again.

Illustration 81

g01199395

The piston has minor scratches in the graphite coating of the skirt.


Page 31 of 53


Illustration 82

Page 32 of 53

g01199403

The piston has minor scratches in the coating of graphite on the skirt.


Illustration 83

g01199408

The piston has loss on the coating of graphite on the skirt.


Use the piston again if the loss of coating on the skirt does not exceed half the area of the skirt. The piston should not be reused if the wear is from hard contact.

Illustration 84

g01199422



Use the piston again if the loss of coating of graphite does not exceed half the area of the piston skirt. The piston mu st also show no signs of wear from hard contact.


Illustration 85

g01199436



The loss on the coating of graphite on the pi ston exceeds half of the skirt. The piston is also showing signs of wear from hard contact.

Illustration 86

g01199491



The loss on the coating of graphite on the piston exceeds half of the skirt.

Illustration 87

g01199571

The piston should not be reused because of scratches that extend into the steel skirt.


Page 33 of 53


Illustration 88

Page 34 of 53

g01199573

The scratches on the piston that extend into the steel skirt that can be felt should not be used again.


Procedure to Inspect Pin Bores During the visual inspection of the piston pin bo re, carefully inspect the snap ring groove of the piston for damage or wear. Do not use the piston again if the groove is excessively worn or damaged. The piston should b e checked in the snap ring groove for undetected wear by making a comparison between the fit of the snap ring in the old piston and fit of the snap ring in a new piston. The piston should not be reused if the effort to turn the snap ring in the used piston is significantly less than the new piston.

Illustration 89

g01199576

A piston with light damage to the pin bore and skirt




Illustration 90

Page 35 of 53

g01199578

A piston with damage to the snap ring groove


Illustration 91

g01199581

The piston has internal damage to the area of the piston pin bore.


Illustration 92

g01199584

The piston has light wear on the edge of the bore, but the measurements of the bore are correct.


Illustration 93

g01199614

The piston has discoloration on the underneath side. Measure the piston pin bores in order to make sure that there is no distortion.



Illustration 94

Page 36 of 53

g01199941

The piston has a wear pattern inside the pin bore.


Do not use the piston again if the scratches can be felt with a fingernail.

Illustration 95

g01199944

The piston shows wear and scratches in the pin bore that can be felt with a fingernail.


Illustration 96

g01199956

There is a track of heavy debris on the piston. The piston pin bore can be used again because the surface of the bore is smooth.



Illustration 97

g01199959

There is embedded debris in the surface of the piston. The piston has debris that can be felt.


Illustration 98

g01199964

The piston has visible scratches that cannot be felt. The surface of the piston is smooth.


Illustration 99

g01199969

The piston has visible scratches and a track of debris that cannot be felt. The surface of the piston is smooth.


Page 37 of 53


Illustration 100

Page 38 of 53

g01199975

The piston has visible scratches that can be seen but not felt. The scratches on the piston have been caused by removing and installing the pin.


Illustration 101

g01200089

The piston bore has a maximum allowable amount of debris.


Illustration 102

g01200090

The piston has severe tracks of debris but the surface of the bore is smooth.


Piston Pin Bores


Illustration 103

Page 39 of 53

g01200091

The piston has impact damage that was caused by mishandling. This type of damage to the piston will result in a crack that will extend to the bore.


Illustration 104

g01200093

The piston shows a wear step in the snap ring groove. This type of damage is caused by a rotating snap ring.


Illustration 105

g01200096


Page 40 of 53

The piston has damage that has been caused by snap ring pliers during the removal of the snap ring.


Two-Piece Pistons Nomenclature

Illustration 106

g01200097

The schematic of a two-piece piston crown and piston skirt (1) Crown (2) Crater (3) Ring Grooves (4) Ring Lands (5) Piston Pin Bushing (6) Skirt (7) Pin Bore in Skirt (8) Top Land (9) Piston Side Relief

Reconditioning Procedure There are several methods for reconditioning minor damage to the piston crown and the piston skirt. Use the method for cleaning that is least aggressive during the process for reconditioning of the piston. A depression results when a part is scratched, nicked, or dented. The scratch, the nick, or the dent can also result in a area that is raised.


Illustration 107

Page 41 of 53

g01200111

Carefully remove the raised metal area that is caused by nicks, dents and scratches. Illustration 107 shows examples of the various types of damage to the piston. In order for the piston to be reused, the piston must be cleaned and the area of metal that is raised must be removed from the surface of the piston. (A) Scratch (B) Raised Metal

The raised areas of the piston can be removed by several methods. The most common methods of removing raised metal are a file, a polishing wheel, or a Scotch-Brite abrasive disc. The file is the most aggressive method for removing raised material. The file is generally recommended for small areas on the surface for material that has been raised more than 0.20 mm (0.008 inch). Use caution to ensure that only the raised material is removed. Be sure that no indentations are left behind from the reconditioning procedure. The polishing wheel and the Scotch-Brite abrasive disc are used to remove small scratches in larger areas. The piston skirt is made from aluminum. In order to reduce the risk of damage to the piston, manual buffing is preferred to a polishing wheel to remove scratches and imperfections. Illustration 132 shows an example of a skirt that was buffed with a Scotch-Brite abrasive disc.

Visual Inspection Make a basic visual inspection of the piston before cleaning. Check the piston for obvious damage. Do not use the piston again if obvious damage is visually inspected. Clean the piston and inspect the piston if no damage is observed.

Handling Damage and Cracking

Illustration 108

g01200118

The piston skirt has dents in the bottom.


The piston may be used again if the raised material can be removed with a file or an oilstone.


Illustration 109

g01201901

The piston has several small nicks that appear as shiny areas.


Use the piston again after removing the raised material.

Illustration 110

g01201911

The piston has several small nicks that are visible.


Use the piston again after removing the raised material.

Illustration 111

g01201914

The piston has a crack in the web area. There is also damage near the pin bore of the piston.


Page 42 of 53


Illustration 112

Page 43 of 53

g01201921

The piston has damage in the area of the pin bore. There is no amount of damage that is allowable in the area of the pin bore.


Illustration 113

g01201926

The piston has a large nick on the surface of the skirt. The damage to the skirt is not repairable.


Illustration 114 The piston has a nick that is too large to repair.


g01201932


Illustration 115

Page 44 of 53

g01201935

The piston has an area of damage that is too large to repair.


Illustration 116

g01201938

The piston has damage to the top surface of the skirt. The piston must not have damage in the joint between the skirt and the crown.


Scuffing Scuffing is not permitted on the piston skirts that are going to be reused. Scuffing is a combination of scratching and embedded material. Do not reuse skirts that have evidence of scuffing.

Illustration 117

g01201941

The piston has a scuffed area that is small and material is also embedded in the surface.



Illustration 118

g01201951

The piston has a scuffed area that is small and material is also embedded in the surface.


Illustration 119

g01201960

A piston that has moderate scuffing


Illustration 120 The piston has moderate scuffing.


g01201967

Page 45 of 53


Illustration 121

Page 46 of 53

g01201972

The piston has severe scuffing.


Discoloration and Markings

Illustration 122

g01201974

The piston has a horizontal marking that is discolored. The horizontal marking does not affect the reusability of the piston.


Use the piston again after the scratches have been polished.

Illustration 123

g01201978

The piston has discoloration due to the cleaning solution.



Illustration 124

Page 47 of 53

g01201990

The piston has horizontal markings that are the result of the manufacturing process. The horizontal markings are not a defect on the piston.


Illustration 125

g01201992

The piston is showing corrosion that is the color of rust.


Use the piston again after polishing the skirt to remove the corrosion. There must also be no corrosion in the piston pin bore or in the groove for the piston snap ring.

Embedded Material There must be no embedded material in the piston. Embedded material can appear as dark hard particles in the surface of the skirt that can scratch the cylinder wall. Embedded material can also appear as light particles on a dark piston. Do not reuse any piston skirt that has embedded material.

Illustration 126

g01201996


Page 48 of 53

Even small amounts of embedded material are unacceptable.

Do not use the piston again. Note: The piston skirt that is shown in Illustration 132 has scratches that can be smoothed through buffing. The piston skirt has embedded material so the skirt cannot be reused.

Illustration 127

g01201997

The piston has a large embedded particle which makes the piston unacceptable.


Illustration 128

g01202022

The piston shows a heavy concentration of embedded particles.


Scratches

Illustration 129

g01202025


The piston has scratches that are not deep and no embedded material is visible.


The piston can be used again after the piston is smooth from buffing.

Illustration 130

g01202026

The piston has scratches that are not deep and no embedded material is visible.


Use the piston again after the piston is smooth from buffing.

Illustration 131

g01202028

The piston skirt is showing scratches that cover a wide area but the scratches are not deep.


Use the piston again after the piston is smooth from buffing.

Illustration 132

g01202031

Page 49 of 53


Page 50 of 53

The piston has a skirt that is smooth from buffing with a Scotch-Brite abrasive disc.


Use the piston again if all the raised material is removed by buffing.

Illustration 133

g01202296

The piston may have scratches that are too deep to salvage. The piston needs to be buffed and the piston needs to be inspected before the piston can be reused.


Use the piston again if there is no visible raised material or embedded material.

Illustration 134

g01202297

The piston may have scratches that are too deep to salvage. The piston needs to be buffed and the piston needs to be inspected before the piston can be reused.


Use the piston again if there is no visible raised material or embedded material.

Illustration 135

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The piston may have small scratches but embedded material is visible.


Crowns The recommendations in this section are based on two-piece piston crowns. To illustrate damage to pistons, some of th e photographs in this section are of one-piece pistons.

Illustration 136

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The piston has damage in the areas between the lands. The piston can be reused because the damage does not extend into the ring groove.


The piston can be used again if the raised material can be removed with a file or oilstone.

Illustration 137

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The damage to the piston extends into the area of the ring groove which cannot be corrected.



Illustration 138

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The damage to the piston is in the area of the ring groove which cannot be corrected.


Illustration 139

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The damage to the piston is on the bottom of the crown which cannot be repaired.


Illustration 140

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The piston has porosity in the bottom of the ring land that does not affect the sealing ability of the ring. Notice the dent at the top of the piston crown. The piston can be reused after the raised material is removed.


Do not use the piston again if the damage to the ring land is by the p iston ring that will affect the shape of the groove.

Illustration 141

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The piston has a dent between the ring grooves that can cause the groove to change in shape.

Visual Inspection of the Piston

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