Maintenance
CAUTION
Leaks are the most common trouble encountered
The ability of the sealant compound to seal
with the integral fuel cells. Slight leaks may sometimes
depends upon its adhesion to metal. Oils and greases
be repaired simply by retorquing (tightening) the bolts
are adhesion breakers and MUST be completely
or screws on either side of the leak. On others it is often
removed from all sealing areas, injection tools, and
necessary to reseal the injection groove around the
your hands when operating or servicing the injection
perimeter of the wing, and replace the O-rings and
gun. Some common contaminants are hair oils, body
washers. Both of these procedures are described in the
oils, and protective hand creams.
following text.
RETORQUING.--You should always retorque to
stop a fuel stain or seepage before attempting to reseal.
Remove the screws from the injection holes of the
The first step in stopping a leak is to retorque the bolts
area to be sealed, and place the sealant gun nozzle tip
or screws for 6 inches on each side of the leaking area
into the countersink of the injection hole. See figure
according to the torque values given in the MIM for the
4-77. Special fittings may be attached between the gun
different size bolts and screws being used. Standard
tip and the barrel for use in areas of limited
bolts are used primarily in attaching wing skin and
accessibility. Hold the gun firmly in position and
should be torqued from the nut side according to
depress the trigger until a plug of sealing compound at
standard torque tables.
least 1 inch in length flows out of the next adjacent
REPLACING SEALS.--If, after retorquing, the
injection screw hole.
leak still persists around a bolt and washer seal, replace
the seal with a new one. Be sure to install a washer
between the bolt head and the seal or leakage will still
occur. Also, be sure to torque the bolts according to the
CAUTION
torque values listed in the MIM.
It is essential that the groove between injection
If the leak is around an O-ring seal, replace the
holes be filled by injection from one direction only. If
O-ring. First, loosen the bolt or screw with a steady
the sealant is forced into these areas from two
pressure. Back out the bolt only as far as necessary to
directions, it is possible that air bubbles will be
remove the O-ring over the head of the bolt or screw.
trapped in the groove. When injection has been
Use petrolatum (Vaseline) if desired. Install a new
inadvertently made from two directions, sealant
O-ring and tighten the bolt to the required torque.
should be injected from one side until a plug of
sealant 5 inches long has been extruded.
The bolt should not be completely removed
because of the possibility of cross threading during
reinstallation. Cross threading could result in the loss of
NOTE: The trigger must be released approxi-
a structural fastener by stripped threads on the nut plate
mately every 30 seconds to allow the gun piston to
or by the threads locking and twisting.
return before another cycle can begin.
REINJECTING SEALANT.--If the leak is at the
Replace the screw in the hole that has just been
perimeter of the tank, reinject the sealant. You should
injected. Proceed in the same manner on the next
use integral fuel tank groove injector compound and fill
adjacent hole (the one from which sealant has
the groove sealant injector gun.
protruded) until the area to be resealed is completed.
NOTE: Be sure that the gun is filled in such a
After all injection hole screws have been installed,
manner that no air is trapped in the sealant. Provide air
remove excess sealing compound from the wing by
pressure at the inlet of the gun according to the gun
scraping with a wood or plastic blade. The area may be
manufacturer's instructions.
cleaned with solvent.
4-50
