TM-9-2815-200-35

ENGINE, WITH CONTAINER:TURBOSUPERCHARGED, DIESEL ,FUEL INJECTION ,90-DEGREE “V” TYPE, AIR - COOLED ,12 - CYLINDER , ASSEMBLY ;MODELS AVDS-1790-2M (2815-856-4996), AVDS-1790-2A AND AVDS-1790-2AM (2815-856-9005)

TECHNICAL MANUAL; DIRECT SUPPORT, GENERAL SUPPORT AND DEPOT MAINTENANCE MANUAL INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS

TM-9-2815-200-35 - Page 344 of 779

6-26. Repair

a. Pistons.

(1)

Replace

pistons

which

are

not

within

limits specified in overhaul standards (table 6-

13).

(2) Replace pistons which are distorted,

cracked, worn, or abraded.

(3) Replace piston if oil holes in the ring

lands cannot be cleared or if lands are damaged

or broken.

(4) Replace pistons that are badly burred,

nicked, or scratched. Remove minor burs, nicks,

or scratches from pistons with crocus

cloth

dipped in dry-cleaning solvent or mineral spirits

paint thinner.

b. Piston Rings.

Piston rings cannot b e

repaired. All piston rings must be replaced with

new rings at engine overhaul.

c. Piston Pins and Plugs.

Replace piston pins

and plugs which are cracked, or have deep nicks

or scratches. Remove minor nicks or scratches

with crocus cloth dipped in dry-cleaning solvent

or mineral spirits paint thinner. Replace piston

pin plugs which have a large wear pattern on the

end. Replace piston pins and plugs not within

limits specified in overhaul standards (table 6-

13).

6-27. Assembly

a.

Check marking on new rings and install the

upper (tapered) compression ring and the two

intermediate compression rings with the marking

“UP” toward the piston dome. Install all rings

using remover and replacer - 5120-795-0177 as

shown in figures 6-44 and 6-45. Use care in

installing rings to avoid damaging ring lands or

distorting rings.

b. Measure side clearance of all new ring (fig.

6-46). Replace rings when side clearance does

not conform to limits specified in overhau l

standards (table 6-13).

Figure 6-46. Checking piston ring side

clearance.

c. Install piston in bore of piston and install a piston pin

plug at each end of piston pin.

d. Select pistons according to weight. Variations in the

weight of pistons in an engine should not exceed 0.5

ounce.

6-50