HYDRAULIC SYSTEM 777 SERVICE MANUAL
2-8 Published 10-01-2012, Control # 045-08
Tightening Hydraulic Connections
• Make sure fittings and O-rings being used are proper
size and style.
• Flush sealing surfaces with clean hydraulic oil to remove
any dirt.
• Carefully inspect threads and sealing surfaces for nicks,
gouges, and other damage. Do not use damaged parts;
they will leak.
• Carefully inspect O-rings for cuts and other damage. Do
not use damaged O-rings; they will leak.
• Always lubricate O-rings when assembling to fittings.
• Be careful not to cut O-rings when assembling to fittings.
Use thimble as shown in Figure 2-6 when assembling O-
ring over threads.
Pipe Thread Connection
1. Apply sealant (Loctite 92 or equivalent) to male threads,
never to female threads. Do not apply sealant to first two
male threads.
2. Tighten fittings about 4-1/2 turns by hand and then 3
additional turns with a wrench.
Table 2-2
Pipe Thread Leakages
O-Ring
Plastic or Metal
Thimble Covering Threads
FIGURE 2-6
S103
CAUTION
Hydraulic System Damage!
Do not use FTE- fluorocarbon tape to seal threads; pieces
of tape will enter hydraulic system and cause damage.
Causes Cures
Fitting loose. Tighten.
Fitting too tight causing thread
distortion.
Replace damaged parts.
Threads on fitting or in port
wrong size.
Use proper size threads.
Threads dirty, galled or nicked. Clean or replace parts.
Straight thread used instead of
tapered thread.
Use proper type and size
thread.
Female threads expanded
from heat.
Tighten when hot.
Fitting loosened by vibration. Retighten.
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