1. General
A.  The nose cowl anti-icing shutoff valve and thermostatic valve are located on the right side of each engine. Access is gained by opening main right cowl panel. The valves are located at approximately the four o'clock position. Installation on both engines are the same.
2.  Removal/Installation Nose Cowl Anti-Icing Shutoff Valve
A.  Remove Nose Cowl Anti-Icing Shutoff Valve (See figure 401.)
(1)  
Pull (open) ENGINE AND WING ANTI-ICE VALVE and ENGINE AND WING ANTI-ICE CONTROL circuit breakers on P18 circuit breaker panel for applicable engine.

(2) 
 Disconnect electrical connector.

(3)  
Remove mounting hardware that attaches shutoff valve to thermostatic valve.

(4)  
Remove mounting hardware that attaches shutoff valve to upper duct.

(5)  
Remove shutoff valve and gaskets.

B.  Install Nose Cowl Anti-Icing Shutoff Valve (See figure 401.)
(1)  
Position shutoff valve and gaskets in place between thermostatic valve and upper duct.

(2)  
Install mounting hardware that attaches shutoff valve to upper duct.

(3)  
Install mounting hardware that attaches shutoff valve to thermostatic valve.

500 
Aug 15/68  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  75-11-21 Page 401 

Nose Cowl Anti-Icing Shutoff Valve and  500 
75-11-21  Thermostatic Valve Installation  Nov 15/67 
Page 402  Figure 401 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

3.  Removal/Installation Nose Cowl Anti-Icing Thermostatic Valve
A.  Remove Nose Cowl Anti-Icing Thermostatic Valve
(1)  
Disconnect lower duct coupling nut.

(2)  
Remove mounting hardware that attaches thermostatic valve to nose cowl anti-icing shutoff valve.

(3)  
Remove thermostatic valve and gasket.

(4)  
Remove reducer fitting and gasket from valve.

B.  Install Nose Cowl Anti-Icing Thermostatic Valve
(1)  
Install new gasket on reducer fitting and install fitting in thermostatic valve.

(2)  
Position thermostatic valve and valve gasket between lower duct and nose cowl anti-icing shutoff valve.

(3)  
Install mounting hardware that attaches thermostatic valve to shutoff valve.

(4)  
Connect lower duct coupling nut.

500 
Nov 15/67  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  75-11-21 Page 403 

ANTI-ICING AIR REAR TUBE - REMOVAL/INSTALLATION
1. General
A.  The anti-icing air system is composed of two identical, but opposite assemblies located on the left and right sides of the engine. Replacement procedure is the same for either assembly.
2.  Remove Anti-Icing Air Rear Tube (Fig. 401)
A.  Lower the engine enough to gain access to the rear anti-icing tube (Ref 71-00 R/I).
B.  Remove bolts securing rear anti-icing air tube to rear compressor outer duct.
C.  Remove four bolts securing anti-icing valve to anti-icing air rear tube assembly. Remove assembly from engine.
NOTE:  Assembly prior to P&WA SB 1536 will incorporate anti-icing air regulator or metering plug in forward end of rear anti-icing tube.
Assembly incorporating P&WA SB 5706 will incorporate gaskets between anti-icing valve and muting tube or support surface. Remove gaskets and note location to facilitate installation.
3.  Install Anti-Icing Air Rear Tube (Fig. 401)
A.  Install rear tube assembly on rear compressor outer duct boss using new gasket, four washers and bolts. Tighten bolts 65 to 75 pound-inches and lockwire.
B.  Secure tube assembly to anti-icing valve with four bolts. Tighten bolts 65 to 75 pound-inches and lockwire.
NOTE:  If assembly is prior to P&WA SB 1536, install anti-icing air regulator or metering plug in forward end of-rear anti-icing tube as applicable.
If assembly incorporates P&WA SB 5706, install gasket between anti-icing valve and rear tube.
C.  Raise and secure engine back in its normal position (Ref 71-00 R/I).
505 
Oct 20/90  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  75-11-41 Page 401 

Engine Anti-Icing Air Rear Tube Installation  505 
75-11-41  Figure 401  Jun 20/87 
Page 402 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

ANTI-ICING AIR FRONT TUBE - REMOVAL/INSTALLATION
1. General
　
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