28-11-00
 ALL  ú ú 01 Page 626 ú Sep 20/97

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757
MAINTENANCE MANUAL

 (d)  Remove the applicable tank access door (AMM 28-11-01/401, AMM 28-11-02/401, AMM 28-11-03/401).
 S 786-066
 (2)  Internal Pressure and Bubble Procedure
 NOTE: Use this procedure only if it is not possible to use the
____ talcum powder procedure to find the external leaks. For example, you can use this procedure if the airplane is defueled. But the recommended procedure to find external fuel leaks is the talcum powder procedure with fuel in the tanks.
 (a)  
Install the pressure plug equipment as follows: 1) Install the vent cover assembly in the surge tank vent. 2) Install the tank cover assembly in the door opening of the

 pressure relief valve in the surge tank (AMM 28-11-03/401).

 (b)  
Install all other fuel tank access doors removed (AMM 28-11-01/401, AMM 28-11-02/401, AMM 28-11-03/401).

 WARNING: BLOW INTO THE MANOMETER HOSE AND MAKE SURE THE WATER LEVEL
_______ CHANGES TO MAKE SURE THE WATER MANOMETER ASSEMBLY OPERATES SAFELY. MAKE SURE THE OPEN END OF THE MANOMETER IS COMPLETELY FREE OF ALL OBSTRUCTIONS. IF THE MANOMETER IS NOT CLEAR, INJURY TO PERSONS OR DAMAGE TO EQUIPMENT COULD OCCUR.
 (c)  
Install plugs in the fuel vent at each wing tip.

 (d)  
Connect the water manometer assembly to the adapter on the tank cover assembly.

 WARNING:_______DO NOT GO INTO A FUEL TANK THAT IS PRESSURIZED. DO NOT USE MORE THAN THE MAXIMUM SAFE PRESSURE OF 5.20 PSIG. IF YOU GO INTO A PRESSURIZED FUEL TANK OR USE MORE THAN THE MAXIMUM SAFE PRESSURE, YOU COULD CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT.

 (e)  
Supply 4.0 psig air pressure to the fuel tank.

 (f)  
Apply the bubble solution to the area out of the fuel tank that you think contains the leak.

 (g)  
Watch the area you think contains the leak for bubbles.

 NOTE: The size of the leak may be such that bubbles form very
____ slowly. It is necessary to watch constantly to find the leak.
 (h)  
Make a mark at the locations where you see bubbles.

 (i)  
Use a moist cloth to remove the bubble solution from the external surface of the fuel tank.

 (j)  
Remove the pressure from the fuel tank.

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 28-11-00
 ALL  ú ú 01 Page 627 ú May 28/99

A
757
MAINTENANCE MANUAL

 (k)  
Remove the pressure plug equipment from the surge tank vent and the door opening of the pressure relief valve in the surge tank.
　
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