5.  Examine Forward Vibration Isolators
A.  Check all metal parts of forward vibration isolator (Detail A, Fig. 602) for evidence of cracks, wear or other damage. Check the conical hole in the isolator for galling, plating wear, and gouging. Check screws for worn or crossed threads or damaged heads.
B.  Replace vibration isolator if alignment pin is missing, loose, or damaged.
C.  Check the molded elastomer parts (Fig 602):
(1)  
If any evidence of sponginess or swelling is found, replace vibration isolator.

(2)  
Check for separations in the bond between elastomer and metal. If individual separations exceed 0.375 inch depth or 1.50 inches length or if total separations exceed 30 percent of bond line, replace vibration isolator.

CAUTION:  USE EXTREME CARE WHEN CHECKING CONDITION OF BOND. AN ACCEPTABLE BOND CAN BE DAMAGED BY USE OF A SHARP PROBE.
NOTE:  Any amount of molded urethane protective coating may be missing and is acceptable for continued service.
(2)  
Do a check of the bond between the elastomer and the ribbed cap.

(a)  
Use medium hand pressure and try to turn the ribbed cap.

(b)  
The bond is satisfactory if the ribbed cap does not turn.

(c)  
If the ribbed cap turns, repair the cap (Barry Controls OHM 71-20-03) or replace the isolator.

(3)  
Inspect elastomer surface for cuts, tears, or gouges. Eight damaged areas up to 0.50-inch diameter by 0.150-inch depth are allowed providing that no more than three are in any quarter of the mount and no bond damage per par. C. (2) is noted in that area.

D.  Using a micrometer, check overall free thickness (steel cap to rubber) at three points around isolator (Detail A, Fig. 602). If average of three readings is less than 1.815 inches, replace the isolator core assembly.
NOTE:  Care must be taken not to depress the elastomer while taking dimensions with the micrometer.
E.  See Fig. 602 for the forward vibration isolators dimensions of mating surfaces.
502 
71-20-0 Page 604  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  May 01/00 

6.  Examine Aft Vibration Isolators
A.  Check the mating surfaces of the isolator housing assembly halves, the conical hole in the flexible core, and all bolt holes for galling, plating wear or gouging. Check bolts for worn or crossed threads or damaged heads. If severe discrepancies are noted, the defective part should be replaced. Check all metal parts for faults.
B.  Magnetic-particle inspect per ASTM E 1444 or BAC 5424, Class B.
CAUTION: DO NOT MAGNAFLUX ANY PART WHICH IS BONDED TO ELASTOMER.
C.  Check elastomer housing:
(1)  
Inspect for scratches, nicks, burrs, chipped plating and corrosion. Repair damaged area (Barry Controls OHM 71-21-03).

(2)  
Check housing flange holes for cracks and wear. Rework flanges holes (Fig 601)

NOTE:  The housing assembly halves are matched pairs. If a serious deficiency is found in one half the other half must also be replaced.

(3)  
Check aft vibration isolator mounting bolt and bolt holes for cracks and wear. Rework bolt holes (Fig 601).

D.  Check elastomer core (Fig 602):
(1)  
Inspect Core metal:

(a)  Inspect for scratches, nicks, burrs and corrosion. If damage does not exceed 0.50 inch diameter by 0.15 inch depth. Repair damaged area (Barry Controls OHM 71-21-03).

(2)
Inspect molded elastomer parts:

CAUTION: USE EXTREME CARE WHEN CHECKING CONDITION OF BOND. AN ACCEPTABLE BOND CAN BE DAMAGED BY USE OF A SHARP PROBE.
NOTE:  Any amount of molded urethane protective coating may be missing and is acceptable for continued service.
(a)  
Inspect elastomer surface for cuts, tears, gouges or abrasions. Minor abrasion is acceptable. No cuts, tears or gouges allowed. Replace elastomer if cuts, tears, gouges or abrasions are observed.

(b)  
Inspect for sponginess or swelling. Replace elastomer core if any evidence of sponginess or swelling is observed.

(c)  
Check for permanent set. Place core assembly in aft housing. Push housing together using moderate hand pressure. Measure distance between housing halves at the parting surface. If the average distance is less than 0.150 inch, replace the core assembly.

(d)  
Check bond between elastomer and ribbed cap by attempting to rotate cap using medium hand pressure.  1) Core assembly is acceptable if ribbed cap does not rotate. If cap rotates, rebond
　
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