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Origins of the Priestman Legacy
Priestman Brothers Ltd., founded in Hull, England in the late 19th century, was a pioneering force in mechanical excavation. Initially known for steam-powered cranes and dredgers, the company evolved through the 20th century to produce hydraulic excavators. By the 1970s, Priestman had become a respected name in the UK construction and mining sectors, known for robust engineering and practical design. The Mustang series emerged during this era as a response to increasing demand for mid-sized hydraulic excavators that could handle both civil and industrial workloads.
The Mustang Series and the 120 Model
The Mustang 120 was part of a lineup that included the Mustang 90 and Mustang 150, each denoting approximate operating weight in hundredweight. The 120, weighing around 15 tons, was powered by a Ford six-cylinder diesel engine—often the 6.2-liter variant used in Ford Cargo trucks. This engine was known for its torque-rich performance and reliability in harsh conditions. Some units were also fitted with Perkins engines, offering similar output but slightly different fuel characteristics.
Key components included:
Design Philosophy and Operator Experience
The Mustang 120 was designed with simplicity in mind. Controls were mechanical-hydraulic, offering tactile feedback and ease of maintenance. The cab, though spartan by modern standards, provided good visibility and straightforward instrumentation. Operators appreciated the machine’s balance and track stability, especially when lifting heavy loads or working on uneven terrain.
One notable feature was the adjustable boom, which allowed for variable geometry depending on the task. This was particularly useful in confined urban sites or when working near overhead hazards like power lines—a concern raised by several operators who noted the importance of maintaining safe clearance.
Field Stories and Anecdotes
In rural Lincolnshire, a Mustang 120 was spotted at a farm auction in the early 2010s, still operational after decades of service. The farmer who owned it claimed it had dug every trench on his property since 1982 and had only required two hydraulic hose replacements in that time. Another operator in Lancashire recalled buying a used unit and being surprised by its dry hydraulics and responsive controls, despite its age.
A humorous incident involved a Mustang parked near high-tension cables, prompting several onlookers to comment on the apparent proximity. While the cables were safely distant, the visual illusion sparked a flurry of safety reminders—underscoring the importance of spatial awareness in excavation work.
Market Position and Decline
During its peak, Priestman sold hundreds of Mustang units across the UK and parts of Europe. However, by the late 1980s, competition from Japanese and German manufacturers—offering more refined hydraulics and electronic controls—began to erode Priestman’s market share. The company eventually ceased production of excavators, and its assets were absorbed into other industrial firms.
Despite this, the Mustang 120 remains a cult favorite among vintage equipment enthusiasts. Its mechanical simplicity, robust build, and historical significance make it a sought-after restoration project. Some units are still in use today, particularly in agricultural and private construction settings.
Maintenance Tips and Common Issues
Owners of surviving Mustangs should consider the following:
The Priestman Mustang 120 is more than an old excavator—it’s a testament to British engineering during a transitional era in construction machinery. While its production numbers were modest compared to global giants, its impact on mid-sized excavation in the UK was significant. For those lucky enough to operate or restore one, the Mustang offers a tangible link to a bygone age of mechanical mastery.
Priestman Brothers Ltd., founded in Hull, England in the late 19th century, was a pioneering force in mechanical excavation. Initially known for steam-powered cranes and dredgers, the company evolved through the 20th century to produce hydraulic excavators. By the 1970s, Priestman had become a respected name in the UK construction and mining sectors, known for robust engineering and practical design. The Mustang series emerged during this era as a response to increasing demand for mid-sized hydraulic excavators that could handle both civil and industrial workloads.
The Mustang Series and the 120 Model
The Mustang 120 was part of a lineup that included the Mustang 90 and Mustang 150, each denoting approximate operating weight in hundredweight. The 120, weighing around 15 tons, was powered by a Ford six-cylinder diesel engine—often the 6.2-liter variant used in Ford Cargo trucks. This engine was known for its torque-rich performance and reliability in harsh conditions. Some units were also fitted with Perkins engines, offering similar output but slightly different fuel characteristics.
Key components included:
- Staffa radial piston hydraulic motors, known for high torque and smooth operation.
- Hamworthy valve blocks, which regulated hydraulic flow with precision and durability.
- Adjustable boom configurations, allowing operators to tailor reach and digging depth for varied tasks.
Design Philosophy and Operator Experience
The Mustang 120 was designed with simplicity in mind. Controls were mechanical-hydraulic, offering tactile feedback and ease of maintenance. The cab, though spartan by modern standards, provided good visibility and straightforward instrumentation. Operators appreciated the machine’s balance and track stability, especially when lifting heavy loads or working on uneven terrain.
One notable feature was the adjustable boom, which allowed for variable geometry depending on the task. This was particularly useful in confined urban sites or when working near overhead hazards like power lines—a concern raised by several operators who noted the importance of maintaining safe clearance.
Field Stories and Anecdotes
In rural Lincolnshire, a Mustang 120 was spotted at a farm auction in the early 2010s, still operational after decades of service. The farmer who owned it claimed it had dug every trench on his property since 1982 and had only required two hydraulic hose replacements in that time. Another operator in Lancashire recalled buying a used unit and being surprised by its dry hydraulics and responsive controls, despite its age.
A humorous incident involved a Mustang parked near high-tension cables, prompting several onlookers to comment on the apparent proximity. While the cables were safely distant, the visual illusion sparked a flurry of safety reminders—underscoring the importance of spatial awareness in excavation work.
Market Position and Decline
During its peak, Priestman sold hundreds of Mustang units across the UK and parts of Europe. However, by the late 1980s, competition from Japanese and German manufacturers—offering more refined hydraulics and electronic controls—began to erode Priestman’s market share. The company eventually ceased production of excavators, and its assets were absorbed into other industrial firms.
Despite this, the Mustang 120 remains a cult favorite among vintage equipment enthusiasts. Its mechanical simplicity, robust build, and historical significance make it a sought-after restoration project. Some units are still in use today, particularly in agricultural and private construction settings.
Maintenance Tips and Common Issues
Owners of surviving Mustangs should consider the following:
- Hydraulic seals: While generally reliable, age-related wear can cause leaks. Replacement kits are available through specialty suppliers.
- Valve block calibration: Hamworthy blocks may drift over time; periodic inspection ensures optimal flow rates.
- Engine servicing: The Ford 6-pot engine benefits from regular oil changes and injector cleaning. Parts are interchangeable with Ford Cargo truck components.
- Electrical safety: Always assess overhead hazards before operating, especially near power lines.
The Priestman Mustang 120 is more than an old excavator—it’s a testament to British engineering during a transitional era in construction machinery. While its production numbers were modest compared to global giants, its impact on mid-sized excavation in the UK was significant. For those lucky enough to operate or restore one, the Mustang offers a tangible link to a bygone age of mechanical mastery.
