Eaton 74318, Repair Information

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6
Motor Trouble Shooting
In trouble shooting a pump and motor system it is necessary to isolate the pump from the motor. This will determine which unit is
actually malfunctioning. A worn pump or motor will both give the same system indication. Therefore, it is advisable to first run a
pressure and flow check on the pump. Making sure it is performing at its operating specifications. The following trouble shooting
suggestions are based on the assumption that the pumps flow and pressure are found within operating specifications.
Problem Possible Causes Correction
1 Motor turns while unloaded but
slows down or stops when load
is applied.
A Scored Valve plate A Remove backplate and examine
bronze surface of valve plate; if
scored, replace valve plate.
B Scored or worn piston shoes. B Disassemble motor, examine
condition of shoes on pistons;
replace rotating kit assembly as
a complete set. Do Not Lap
pistons.
C Low pressure. C Check relief valve for proper
pressure setting; adjust or
replace relief valve.
2 Motor will not turn. A Severely scored internal parts A Disassemble motor completely.
Inspect all parts, clean all parts,
replace all worn parts and flush
hydraulic system.
3 Motor will not hold load when
system is in neutral position.
A No make up fluid from charge
pump.
A Check charge pressure.
B Scored valve plate or piston
shoes.
B Disassemble motor and examine
valve plate and piston shoes,
replace as required.
4 Excessive case drain flow. A Excessive internal wear in
motor.
A Disassemble motor, inspect
parts and replace as necessary.
Case drain flow should not
exceed 7.6 L/m [2 gal/m] at full
pressure.