Coolant in the Turbo Inlet on a Volvo 700B Motor Grader

[MikePhua]

The Volvo 700B and Its Place in Grader History
The Volvo 700B motor grader was part of Volvo Construction Equipment’s push into the mid-size grader market during the late 1980s and early 1990s. Designed for road maintenance, site grading, and snow removal, the 700B featured a six-wheel drive configuration, hydraulic blade controls, and a turbocharged diesel engine. While not as widely adopted as Caterpillar’s 140 series or Champion’s C-series, the 700B found a niche in municipal fleets and small contractors across Canada, Scandinavia, and parts of Australia.
Volvo CE, a division of the Swedish automotive giant, has long been known for its emphasis on operator comfort and safety. The 700B was equipped with a spacious cab, ergonomic controls, and a relatively quiet drivetrain. However, its limited parts availability and complex turbo plumbing have made it a challenge for long-term maintenance—especially in remote regions.
Terminology Annotation
- Turbo Inlet: The air intake side of the turbocharger, where filtered air enters before being compressed and sent to the engine.
- Hydrolock: A condition where liquid enters the combustion chamber, preventing piston movement and potentially damaging internal components.
- Intercooler: A heat exchanger that cools compressed air from the turbo before it enters the engine, improving efficiency and reducing knock.
- Air Cleaner: A filtration unit that removes dust and debris from intake air before it reaches the turbocharger.
Unusual Coolant Intrusion and Initial Observations
One operator discovered antifreeze inside the turbo inlet and even in the air cleaner housing—a highly abnormal condition. Upon attempting to start the engine, it appeared hydrolocked, suggesting that coolant had entered the cylinders. This raised immediate concerns about internal engine failure, sabotage, or a catastrophic cooling system breach.
Initial theories included:

• Sabotage: Someone may have poured coolant directly into the air intake, either maliciously or mistakenly.
  
• Cracked Cylinder Head or Liner: Coolant could have leaked into the combustion chamber and then backflowed through an open intake valve.
  
• Intercooler Failure: If the engine is equipped with a liquid-cooled intercooler, a rupture could allow coolant into the intake stream.
  
• Pressure Surge: A failed head gasket or cracked block could force coolant into the intake manifold under pressure.
  

A Story from the Field
In Alberta, a grader operator returned from a weekend only to find his Volvo 700B refusing to start. Upon inspection, he found green coolant pooled in the air cleaner and turbo inlet. The machine had been parked in a public yard, and suspicion of vandalism arose. However, the radiator level was still full, and no signs of forced entry were found. A mechanic later discovered that the intercooler had ruptured internally, allowing coolant to migrate into the intake system. The engine was saved by not forcing a start, and the intercooler was replaced with a custom-fabricated unit due to parts scarcity.
Diagnostic Strategy and Inspection Points
To determine the source of coolant intrusion:

• Inspect the radiator and coolant reservoir levels. A drop may indicate internal leakage.
  
• Remove the air cleaner and check for residue on the filter element and housing.
  
• Pull the intake piping and inspect for coolant pooling or staining.
  
• Remove glow plugs or injectors and turn the engine manually to check for hydrolock.
  
• Pressure test the cooling system to identify leaks under static conditions.
  
• Inspect the intercooler (if liquid-cooled) for internal rupture or corrosion.
  
• Check cylinder compression and perform a leak-down test to identify head gasket or liner failure.
  

Preventative Measures and Recommendations
To avoid similar failures:

• Park equipment in secure, monitored areas to deter tampering
  
• Install intake covers during long-term storage to prevent contamination
  
• Flush and replace coolant annually, especially in machines exposed to freeze-thaw cycles
  
• Inspect intercoolers and intake plumbing during routine service intervals
  
• Use coolant with corrosion inhibitors compatible with aluminum and mixed-metal systems
  
• Train operators to recognize signs of hydrolock and avoid forced starts
  

If sabotage is suspected, document the incident and inspect surrounding equipment for similar signs. In some cases, insurance claims may require forensic analysis of fluid samples and mechanical damage.
Industry Trends and Legacy Support
As of 2025, Volvo CE has shifted focus toward smart graders with GPS blade control, telematics, and hybrid drivetrains. Support for legacy models like the 700B is limited, with parts often sourced from salvage yards or custom fabricators. Some operators have retrofitted CAT or Cummins engines into Volvo frames to extend service life.
Meanwhile, grader fleets in northern climates continue to rely on older machines for seasonal work. The simplicity of mechanical controls and the durability of steel frames make them ideal for gravel road maintenance and snow clearing—provided cooling systems are maintained and protected.
Conclusion
Coolant in the turbo inlet of a Volvo 700B is a rare and serious issue, often pointing to internal failure or external interference. With careful diagnosis and methodical inspection, the root cause can be identified and addressed. Whether it’s a cracked intercooler, a failed head gasket, or an act of sabotage, the key is to act quickly and avoid forcing the engine to start. The 700B may be aging, but with proper care and a bit of ingenuity, it can still earn its keep on the road.