Amperage _______________(Subtract System A Basic Current First)
 Flow _______________ cc/minute (Value 13)
 (c)  Subtract the Value 12 flow from the Value 13 flow. The difference must be less than 1500 cc/minute.
 S 796-071
 (26) Do these steps to find the leakage for the landing gear and steering valve:
 (a)  
Put the LANDING GEAR lever in the DN position.

 (b)  
Read the amperage or the flow value and write it here:

 Amperage _______________(Subtract System A Basic Current First)
 Flow _______________ cc/minute (Value 14)
 (c)  Subtract the Value 13 flow from the Value 14 flow. The difference must be less than 2100 cc/minute.
 S 796-072
 (27)
 If you found leakages that are too large, you can use procedure 3 to help you find the parts that are bad.

 S 846-073

 (28)
 Do the procedure to put the airplane back to its usual condition.

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737-300/400/500MAINTENANCE MANUAL
 TASK 29-00-00-796-074
 6.  Part Internal Leak Check (Procedure 3)________________________
 A. General
 (1)  
Use this procedure to find the internal leakage of each part or a small group of parts.

 (2)  
To find the condition of the parts of the hydraulic system you compare the leakage you measured to the maximum leakage. If you find a leakage that is more than the maximum, you must replace the parts that have too much leakage. Refer to Chapter 27 (Flight Controls), Chapter 32 (Landing Gear), or Chapter 22 (Autoflight) for the applicable removal and installation procedures.

 (3)  
You must find the changes in the flow of hydraulic fluid (during different conditions of operation) to find the internal leakage rate for each part. There are three procedures to measure the flow: the ammeter procedure, the flowmeter procedure, and the amp-clamp and multimeter procedure.

 (a)  
To use the ammeter procedure, you connect an ammeter in series with one phase of the motor on the electric motor-driven pump (EMDP). To find the flow you measure the current subtract the applicable system basic current, and use Figure 603 to change it to a flow.

 (b)  
To use the flowmeter procedure, you install a flowmeter on a hydraulic service cart and read the flow from it.

 (c)  
To use the amp-clamp and multimeter procedure, you put the amp-clamp adapter around one of the wires connected to a relay for the EMDP. You then read the current on the multimeter (that is connected to the amp-clamp adapter) subtract the applicable system basic current, and use Figure 603 to get the flow. One person can do this procedure from the Control Cabin.

 (4)  
When you read the ammeter, make a record of the value (on the data sheets in this manual) to the nearest 0.1 ampere. Use Figure 603 to change current to flow.

 (5)  
When you read the flowmeter, make a record of the value (on the data sheets in this manual) to the nearest 100 cc/minute.

 B. References
 (1)  
AMM 29-15-00/201, Hydraulic Systems A, B, and Standby

 (2)  
AMM 78-31-00/201, Thrust Reverser System

 C. Access
 (1)  Location Zones
 101/102 Control Cabin
 216/217 Main Wheel Wells

 D. Procedure
 S 846-075
 (1)  
Do the Prepare for an Internal Leak Check procedure.

 S 866-076

 (2)  
Close the No. 1 through No. 6 isolation valves (in the tail compartment) (Fig. 604).

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A 737-300/400/500MAINTENANCE MANUAL
 S 866-078
 (3)  AIRPLANES WITH ISOLATION VALVES FOR THE LANDING GEAR;
 Close them (Fig. 604).
　
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