RADIATOR GP 10R0739 - Caterpillar

TECHNICAL INFORMATION BULLETIN JUNE 23, 2004
PRODUCT FAMILY
Track-Type Tractor D6R (AEM104)
D6R (AFM125, AFM126)
D6R (AGM105)
D6R (AAX667-AAX744)
D6R (ADE520-ADE576, ADE578-ADE593)
D6R (AEP350-AEP379, AEP381-AEP392)
D6R (ACJ109-ACJ111)
D7R (ACS604-ACS612)
D7R (AGN684-AGN720, AGN722, AGN00723)
D7R (AEC765-AEC778)
D7R (ABJ586, ABJ587)
D8R (6YZ1780-6YZ1848, 6YZ1850-6YZ1860)
D9R (ACL1090-ACL1114, ACL1116)
D9R (ABK964-ABK994, ABK996-ABK1001)
Component Code(s) 5102SUBJECT: D6R ? D9R Lift Cylinder Pistons May Have Defective Bypass Valves
PROBLEM:
The bypass valve in the piston assembly for the D6R to D9R may be manufactured incorrectly. Some pistons were manufactured that will not allow the bypass valve to open when the cylinder rod has completely retracted. When the bypass valve in one cylinder opens it will stop the movement of both cylinders. Failure of the valve to open can cause damage to the machine when the blade is tilted and the movement of both cylinders does not stop when one of the lift cylinders reaches the end of its stroke.
When the blade is tilted and both cylinders try to fully retract, the blade tries to move to the horizontal position and the front structure tries to move to the tilted position. Twisting in the front structure will cause the fan shroud to deflect. When the deflection is sufficient, the fan blades will come in contact with the shroud and the radiator.
The following cylinder part numbers can have the incorrect bypass valve problem:
127-8931 Lift Cylinder for D6 Std
129-4258 Lift Cylinder for D6 LGP
129-1908 Lift Cylinder for D7 Std
129-4259 Lift Cylinder for D7 LGP
6E-1102 Lift Cylinder for D8 Std
165-8633 Lift Cylinder for D9 Std
SOLUTION:
In order to determine whether or not this problem is present on a machine, the test outlined below must be performed on each machine. Every machine in the serial number range must be tested. If a cylinder is found to be bad, the piston assembly in the cylinder must be replaced.
Test Procedure for Blade Lift Cylinder Bypass Valve Operation:
Disconnect the blade lift cylinder from the blade, if the blade is installed on the machine.
Install a safety stop on one of the cylinder rods that will prevent the cylinder from fully retracting. To prevent bending in the rod, during this test, it is important to use a stop collar that goes around the rod and produces even loading on both sides of the yoke. Be sure that the safety stop is securely installed on the rod.
Connect a pressure gauge capable of 4000psi to the HB gauge adapter (pressure tap) for pump signal pressure.
Start the engine and run the engine at low idle speed.
Using the blade lift controls, retract the blade lift cylinder rod until one lift cylinder is completely retracted. The other lift cylinder will not be fully retracted because a stop is installed on the rod.
Continue to operate the blade lift control. Record the pressure that is observed on the gauge. The bypass valve is good on the fully retracted cylinder, if the HB pressure (pump signal pressure) is approximately 200psi at low idle engine speed and approximate 1200psi at high idle engine speed. The bypass valve is bad on the fully retracted cylinder, if the HB pressure is greater than 2000psi.
Repeat this operation several