Why Hydraulic Cylinder Seals Leak on Low-Hour Machines and What to Do About It

[MikePhua]

The Ford/New Holland 675E and Its Hydraulic System
The Ford/New Holland 675E backhoe loader was introduced in the mid-1990s as part of New Holland’s push to modernize its compact construction equipment lineup. With a robust hydraulic system, extendable dipperstick (Extendahoe), and a reputation for durability, the 675E was widely adopted by municipalities, contractors, and agricultural users. Its hydraulic cylinders—used for boom lift, bucket curl, stabilizers, and the Extendahoe—are built around conventional piston-and-rod designs with internal seals that rely on consistent use and fluid pressure to maintain pliability.
Despite its reputation, even low-hour machines like a 1997 675E with under 500 hours can exhibit seal leakage, especially after long periods of inactivity. This phenomenon often surprises owners who expect pristine performance from such lightly used equipment.
Why Seals Leak After Long Storage
Hydraulic seals are typically made from nitrile rubber (NBR), polyurethane, or Viton compounds. These materials are designed to withstand high pressure, temperature fluctuations, and fluid compatibility. However, they also depend on regular movement and fluid exposure to remain flexible.
When a machine sits idle for years:

• Seals dry out and lose elasticity
  
• Fluid drains away from contact surfaces
  
• Micro-cracking can occur due to ozone exposure
  
• Cold temperatures exacerbate shrinkage and hardening
  

In such cases, seals may leak immediately upon startup or begin dripping steadily as pressure builds. The Extendahoe cylinder, which sees less frequent use, is often the first to show signs of leakage.
Cold Weather and Seal Behavior
Cold temperatures thicken hydraulic oil and reduce seal flexibility. In climates where winter temperatures drop below freezing, seals may leak temporarily until the system warms up. However, persistent leakage after warm-up suggests permanent seal degradation.
Contrary to popular belief, 40°F is not considered extreme for hydraulic systems. Logging equipment and cranes often operate at -20°F without seal failure, provided the seals are in good condition and the oil is properly rated. In the case of the 675E, temperatures ranging from -15°F to 20°F during startup likely accelerated the exposure of compromised seals.
Can Seals Reseal Themselves
Some operators hope that seals will “recondition” themselves after a few hours of operation. While new seals may leak briefly during break-in, aged seals rarely recover. Once the rubber has hardened or cracked, no amount of fluid cycling will restore its sealing ability.
Running the machine to warm the oil may reduce leakage temporarily, but it will not reverse the underlying deterioration. In fact, continued operation with leaking seals risks oil loss, contamination, and eventual cylinder scoring.
Inspection and Repacking Strategy
Before repacking, inspect the cylinder rods for:

• Chrome pitting or scoring
  
• Dirt or debris buildup near the gland
  
• Rod misalignment or side loading
  

If the rods are clean and straight, repacking is the logical next step. OEM seal kits are available for most Ford/New Holland cylinders, but some operators report premature failure even with factory kits. Alternatives include:

• Aftermarket seal kits with upgraded compounds
  
• Custom seal fabrication from hydraulic shops
  
• Switching to double-lip rod seals for added protection
  

Repacking involves:

• Removing the cylinder from the machine
  
• Disassembling the gland and piston
  
• Cleaning all components thoroughly
  
• Installing new seals with proper orientation
  
• Reassembling with torque specs and fluid testing
  

Experienced mechanics recommend replacing seals in pairs (rod and piston) and inspecting the wear rings and backup rings for deformation.
Field Experience and Practical Advice
A technician in North Carolina noted that Ford backhoe cylinders often leak after minimal use. He repacked two cylinders with OEM kits, only to see them leak again within 30 hours. Switching to a different seal supplier improved longevity. He also observed that cold snaps triggered leaks in otherwise healthy cylinders, especially on larger machines like a 220-class trackhoe.
Another operator in Wisconsin compared seal behavior to flat spots on tires—stiff seals that have sat for years may need time to flex, but if they’re cracked or hardened, they won’t recover. He emphasized the importance of inspecting seals after storage and not assuming low hours equals good condition.
Preventive Measures and Long-Term Reliability
To extend seal life:

• Operate the machine monthly to circulate fluid
  
• Store indoors or under cover to reduce ozone exposure
  
• Use hydraulic oil with anti-oxidation additives
  
• Avoid pressure washing near cylinder glands
  
• Replace seals proactively every 5–7 years regardless of hours
  

Adding rod wipers or protective boots can reduce contamination and extend seal life. Monitoring for early signs of leakage—such as wet glands or slow drift—can prevent costly repairs.
Conclusion
Hydraulic cylinder seal leakage on low-hour machines like the Ford/New Holland 675E is often caused by age, inactivity, and cold weather—not wear. While some hope seals will reseal themselves, the reality is that hardened rubber rarely recovers. Repacking with quality seals and inspecting rod condition is the most effective solution. With proper maintenance and preventive care, even vintage machines can operate leak-free and reliably for years to come.