Hydraulic Pump Issue on Link Belt HTC 8640: Need Help Finding Replacement Part #F7J0015SPL

Are you neglecting to engage the "unloader" on your pump? It's possible you are referring to a relief port, but most relief valves do not discharge oil externally. They usually just redirect oil back into a return line to the tank. The activation of a relief valve is not necessarily a sign of a weak pump; a weak pump would not generate enough pressure to trigger a relief valve release. Before assuming the pump is faulty, it is recommended to conduct pressure tests and diagnostic checks. However, without more details, it's difficult to provide specific advice. I have experience with 2 8640 HL pumps, so if you need specific pump numbers, I can check mine for reference.

• 09-10-2024
• crane operator

In terms of pump drives, my two 8640 units are equipped with Allison transmissions, with the pumps mounted directly on top of the transmission as mentioned by CraneMechanic73. However, I am unsure of how the manual transmission 8640 units operate in comparison.

• 10-10-2024
• crane operator

The unloading valve, depicted as item 6 in the diagram, experienced internal failure leading to its malfunction. While the relief valve functions as expected, there was a consideration of the unloading valve operating in a similar manner to those found in compressors.

• 10-10-2024
• Nicholift

Commonly, the valve labeled as the "unloading" valve in the schematic is usually a spring stack serving as a buffer. This component helps absorb hydraulic shock when the crane is rapidly lowering and suddenly comes to a halt. Is it possible that you are a novice operator who hasn't fully mastered the controls yet?

• 10-10-2024
• crane operator

After completing heavy equipment training in Dothan, Alabama following his time in the Army, he attended a crane school in Wisconsin. He then gained experience working on projects for big companies like Amazon and Google in Wyoming with a mobile crew. He spent some time back in Northern Illinois before moving to Wisconsin to work for another company. Eventually, he seized the opportunity to relocate to Florida. A year later, he decided to start his own business, which he has been running successfully for a few months now. A crane mechanic from his former workplace in Wisconsin suspects that a stuck valve (possibly due to debris) is causing a high-pressure issue in the crane's system. As a commercial truck repair specialist in Northern Illinois with no experience working on cranes, it's challenging to diagnose the issue over the phone without firsthand knowledge of the equipment or its systems. However, I am grateful for the insights you are providing, as they will enable me to assist him better in resolving the problem.

• 11-10-2024
• Nicholift

The stack in the pictures appears to be the winch stack for a single winch machine. Providing more information will make it easier to diagnose remotely. Hopefully, the issue is not caused by debris in the system, as that can be quite troublesome.

• 11-10-2024
• crane operator