Volvo BM646: A Classic Yet Under-Documented Machine

[MikePhua]

The Volvo BM646, a member of Volvo’s BM (Bolinder-Munktell) series, has earned its place in the history of construction and agriculture machinery. While it may not be as widely known as some other models in the Volvo lineup, it still holds value for collectors, operators, and those who need to maintain and operate it today. One of the main challenges with the Volvo BM646 is the limited availability of detailed manuals and resources, particularly through the ProSis system, which makes servicing and troubleshooting more difficult. In this article, we will dive into the history of the Volvo BM646, the difficulties faced by those who maintain it, and the steps you can take to get the most out of this robust machine.
The History of Volvo BM646
Volvo’s history in construction machinery dates back to the early 20th century. Originally, Volvo's equipment was marketed under the name BM (Bolinder-Munktell), which merged into the larger Volvo brand over time. The BM646 was produced as part of a line of wheel loaders and was particularly popular in the 1960s and 1970s. The machine is known for its robustness and versatility, often used in various industrial and agricultural settings.
The BM646 was designed for heavy lifting, material handling, and earthmoving tasks. Powered by a diesel engine, the machine was capable of operating for extended periods in harsh conditions, thanks to its durable design. While newer models have replaced the BM646, many still remain in operation due to their reliability and the heavy-duty build quality characteristic of Volvo machinery.
Challenges with the Volvo BM646’s Documentation and Support
One of the most common issues that operators and mechanics face with the Volvo BM646 is the lack of easily accessible documentation. The Volvo ProSis system, which offers online service and maintenance manuals for Volvo machinery, does not include the BM646 in its database. As a result, finding accurate information, diagrams, or troubleshooting guides can be difficult. This issue is compounded by the fact that the machine is somewhat outdated, and parts or service recommendations may not always be readily available through traditional channels.
The lack of digital resources, combined with the machine’s age, makes it challenging to find detailed repair guides or comprehensive manuals for tasks such as engine diagnostics, hydraulic system repairs, or electrical troubleshooting. This is especially true for those who may not have direct experience with older Volvo machines.
What You Can Do to Overcome the Lack of Documentation
Although accessing official manuals and information might be a challenge, there are still several strategies that operators and mechanics can use to maintain and troubleshoot the Volvo BM646.

1. Seek Out Third-Party Resources: There are several third-party websites, forums, and communities dedicated to vintage Volvo machinery, where experienced operators share manuals, troubleshooting advice, and solutions to common problems. Websites that focus on older construction machinery may offer downloadable PDFs, repair guides, and user-shared diagrams for machines like the BM646.
   
2. Contact Volvo Dealers or Service Centers: Although the BM646 may not be listed in the ProSis system, it is still worth reaching out to Volvo dealers and service centers that specialize in older machines. These experts may have archived documents or be able to provide technical support for machines that are no longer in active production.
   
3. Utilize Maintenance Manuals from Similar Models: While the BM646 may not have a dedicated manual available in ProSis, other models from the BM series, such as the BM630 or BM700, may have similar systems and components. Often, the mechanics of these machines overlap, so their manuals could serve as useful references for general maintenance and repairs.
   
4. Consider a Retrofit or Upgrade: For those who rely heavily on the BM646 for daily operations, it may be worthwhile to look into retrofitting the machine with modern equipment or systems. For example, updating the electrical system or adding more modern hydraulic components can make maintenance easier and increase the machine’s operational efficiency.
   
5. Document Your Own Maintenance: Given the limited availability of official manuals, keeping a record of your own maintenance and repair work is critical. Take detailed notes of parts replacements, repairs, and adjustments that you make to the machine. This self-created record can serve as a useful reference for future repairs.
   

Engine and Powertrain of the BM646
The Volvo BM646 is typically powered by a diesel engine, which was designed to offer reliability and long operational hours. Though specific engine models can vary depending on the production year and market, these machines typically feature engines with an output of around 90 to 110 horsepower, making them suitable for lifting and hauling operations in a variety of work environments.
Key Specifications:

• Engine Type: Diesel
  
• Horsepower: 90-110 hp
  
• Transmission: Hydrostatic or mechanical gear transmission (depending on model year)
  
• Lifting Capacity: 2,000-3,000 kg (depending on bucket configuration and other factors)
  
• Tire Size: 17.5 x 25 (common for this class of equipment)
  

This setup allows the machine to handle a wide range of tasks with solid lifting capability. However, its age means that wear and tear on engine components like the fuel system, starter motor, and alternator is not uncommon, and parts replacement may be necessary to maintain optimal performance.
Common Problems and Solutions
Despite being a reliable piece of equipment, the Volvo BM646 does experience certain issues, particularly due to its age. Some of the most common problems include:

1. Engine Overheating: Overheating is a common issue in older machinery, often due to clogged radiators or cooling system failures. Regular cleaning and maintenance of the cooling system can help prevent this issue. Check coolant levels regularly and inspect the radiator for debris or damage.
   
2. Hydraulic System Failures: The hydraulic system, which powers the loader’s bucket and other attachments, may experience leaks or pressure issues over time. Regularly checking the hoses, seals, and fluid levels can prevent serious hydraulic failures. If a hydraulic component fails, ensure that replacement parts are compatible with the BM646’s specifications.
   
3. Transmission Issues: Some operators report issues with the machine’s transmission, such as slipping or difficulty shifting gears. Regular maintenance, including fluid changes and checks for leaks, can help prevent transmission problems.
   
4. Electrical Failures: The electrical system in the BM646 may be prone to failure, particularly with older wiring, connectors, or switches. A thorough inspection of the electrical system, including the battery, alternator, and wiring, is necessary to ensure proper function.
   

The Legacy of Volvo BM Machines
Volvo’s BM series has left a lasting impact on the heavy equipment industry. Despite the challenges of maintaining older machines like the BM646, the legacy of reliability, performance, and durability lives on in modern Volvo machinery. The shift from the BM series to Volvo-branded equipment reflects the company’s growth and evolution, but for those still operating machines like the BM646, there is a deep sense of appreciation for the engineering that went into creating these workhorses.
Conclusion
The Volvo BM646 remains a valuable machine for those who are able to maintain and operate it despite the lack of readily available documentation. Although the absence of resources like the ProSis system can make repairs and maintenance challenging, with the right strategies—such as consulting third-party resources, working with experts, and maintaining a record of repairs—operators can continue to get the best performance out of this classic Volvo machine.