Restoring Weather Seals on a 1980 CAT D5H Dozer: Gasket and Molding Solutions for Legacy Equipment

[MikePhua]

Introduction: The Importance of Cab Seals in Heavy Equipment
In the world of heavy machinery, operator comfort and equipment longevity often hinge on the smallest components—like door gaskets and window moldings. For older equipment such as the 1980 CAT D5H dozer, maintaining the cab’s weatherproofing is not just about keeping out dust and rain, but also preserving heating and cooling efficiency, reducing noise, and extending the machine’s operational life.
These seals, originally custom-fitted at the factory, deteriorate over decades of exposure to UV radiation, chemicals, weather, and constant vibration. Finding replacements can be challenging, especially for discontinued models like the early D5H. However, with the right approach and a little ingenuity, operators can restore their dozer cabs to a comfortable and protected state.
Understanding the Components: Gaskets, Moldings, and Their Roles

• Cab Door Gaskets
  • Typically made of rubber or neoprene.
    
  • Seal the perimeter of the door to prevent air, water, and dust intrusion.
    
  • Help maintain interior cab pressure for HVAC systems.
    
• Window Moldings (Glazing Seals)
  • Rubber or plastic strips that secure glass in metal frames.
    
  • Provide water-tight sealing and cushion glass against vibration.
    
• Edge Trim Seals
  • Used around sharp metal edges to both protect seals and provide additional weatherproofing.
    

Challenges in Replacing Gaskets on Older Equipment

• Obsolete OEM Parts
  • Parts for older Caterpillar models are often no longer manufactured or stocked by dealers.
    
  • Original part numbers may be missing or superseded multiple times.
    
• Cab Variations
  • Over the years, even the same model could have cab designs from different manufacturers (e.g., ROPS-integrated vs. aftermarket cabs), affecting seal dimensions.
    
• Inconsistent Fitment
  • Universal seals may not match factory contours, requiring modification.
    

Aftermarket and Custom Solutions
Owners of older CAT equipment have found success through alternative sources, including:

• Automotive and Truck Seal Suppliers
  • Vendors like Metro Moulded Parts or Steele Rubber Products offer universal weatherstrip profiles that can be cut to length and installed on heavy equipment.
    
• Industrial Rubber Distributors
  • Companies like McMaster-Carr and Trim-Lok carry a wide range of edge trims, bulb seals, and weatherstripping profiles that can fit dozer doors and windows.
    
• Junkyard Salvage or Machine Yards
  • In some cases, operators have salvaged seals from donor machines of similar vintage.
    
• Custom Fabrication
  • Some owners have taken measurements and made molds or templates to have seals custom-extruded or retrofitted.
    

Steps to Measure and Replace Door Seals

1. Remove Existing Gasket
   • Carefully peel or cut away the old seal without damaging mounting surfaces.
     
2. Clean the Surface
   • Use solvent to remove old adhesive and grime.
     
3. Measure Groove Dimensions
   • Record the channel width and depth. Measure door perimeter length.
     
4. Select Matching Profile
   • Choose a seal with similar bulb diameter, grip range, and material composition.
     
5. Dry Fit and Trim
   • Test-fit the new gasket before applying adhesive or clips.
     
6. Install with Adhesive or Clips
   • Use weatherstrip adhesive or push-in retainers as appropriate.
     
7. Inspect Fitment and Seal Integrity
   • Close the door and check for wind noise or gaps.
     

Real-World Story: A Dozer in the Rockies
A forestry contractor in Colorado restored a 1980 D5H used for trail clearing and fire break maintenance. After years of operating in harsh winter conditions, the cab’s seals had completely failed. Wind whistled through the doors and snow would blow into the operator’s compartment. With no OEM seals available, the owner turned to an RV seal supplier and matched a double-bulb seal intended for bus hatches. Combined with an industrial U-channel edge trim, the seal fit snugly and kept the cab warm through another season of sub-zero starts and rugged terrain.
Terminology Explained

• Gasket: A flexible seal used to close gaps and prevent fluid or air leakage.
  
• Molding: A trim piece, often rubber or plastic, used to secure glass or panel edges.
  
• ROPS (Roll-Over Protective Structure): A safety cab frame protecting the operator in case of a rollover.
  
• Bulb Seal: A type of gasket with a hollow rubber tube (“bulb”) that compresses to form a seal.
  
• U-Channel Trim: A seal with a U-shaped base that grips metal edges.
  

Conclusion
Restoring door and window gaskets on a 1980 CAT D5H dozer is a worthwhile endeavor that greatly improves operator comfort and cab durability. While OEM parts may be hard to find, a wide array of universal and custom options exist through industrial suppliers. With accurate measurements and a bit of experimentation, owners can bring new life to their vintage equipment—often better than when it left the factory.