Detecting Oil Leaks and Residue Build-Up with Borescope Technology

When servicing aircraft engines — whether on helicopters, business jets, or private planes — one of the biggest unseen risks is internal oil leaks or residue build-up. Such issues can silently degrade engine performance, create corrosion, or indicate seal failures. That’s why remote visual inspection (RVI) tools are increasingly used by maintenance professionals to get an unfiltered look inside engines without disassembly. Modern borescopes give inspectors high-resolution access to internal compartments, enabling early detection of oil leaks, carbon deposits, or residue accumulation that would otherwise go unnoticed. External sources confirm that borescopes are widely adopted in aviation maintenance for these very purposes.

In this blog, we explore how technicians use borescopes to locate internal oil residue, carbon deposits, and leaks in hard-to-reach engine compartments — and why this capability is essential for engine safety and longevity.

The Borescope Advantage: Access, Clarity, Non-Destructive Inspection

A borescope — or videoscope/inspection camera — is a slender tube equipped with a light source, lens, and video camera that transmits real-time images to a monitor. This allows technicians to peer into narrow or complex internal engine spaces without tearing the engine apart.

In the context of aircraft engines, that means components such as combustion chambers, oil pathways, bearing housings, gearbox oil passages, and turbine casings can be visually inspected for leaks, residue, or abnormal deposits. Using a borescope helps avoid extensive disassembly, reduces maintenance downtime, and minimizes the risk of introducing new faults — making it a core non-destructive testing (NDT) technique in aviation.

Spotting Oil Residue, Leaks, and Carbon Deposits

One primary application of borescope technology for engine maintenance is detecting oil leaks or oil residue inside internal passages, combustion chambers, and around seals or gaskets. According to a recent overview of aviation borescope inspections, leaks or oil-line blockages discovered with a borescope may prevent engine overheating or even seizure.

When oil seeps into areas under heat or pressure — such as combustion chambers or turbine sections — it can leave telltale residue. A skilled technician using a borescope can identify discolored surfaces, oil films, wetness around seals or joints, or pooling of residue in areas where oil should not be present. These indicators can signal worn seals, cracked housings, or failing gaskets. Similarly, carbon buildup and combustion residue, which often accumulate on valves, combustion chambers, or piston crowns, can be visualized and assessed.

In internal combustion engines — not just in aviation but also in automotive contexts — borescopes are widely used to inspect cylinder walls, valves, and combustion chambers for carbon deposits and oil contamination.

Why Early Detection Matters for Engine Health and Safety

Oil leaks and residue buildup are not always immediately catastrophic — but they erode performance, reduce reliability, and may lead to bigger failures if left uncorrected. In aircraft engines, where operating conditions are extreme (high temperature, high pressure, rapid cycles), even small leaks or residue accumulation can have outsized consequences. According to industry guidance, regular borescope inspections are critical to identifying fuel or oil pathway leaks, carbon buildup, and components at risk of thermal or mechanical failure — before these conditions evolve into major issues.

By catching residues early, maintenance teams can clean, reseal, or repair affected parts — preventing corrosion, heat-related damage, improper lubrication, or foreign-object ingestion. This proactive approach enhances engine longevity, ensures performance stability, and reduces the risk of unscheduled downtime or catastrophic failure.

Moreover, when inspections are documented via video or still images, the resulting records become a valuable part of maintenance logs — supporting trend monitoring, regulatory compliance, and informed maintenance decisions.

Best Practices: How Technicians Use Borescopes to Detect Oil Residue and Leaks

To achieve reliable results when inspecting for oil leaks or residue, technicians generally follow a structured protocol:

• Ensure the engine is cool and de-energized: This avoids heat damage to the borescope and ensures inspection safety.
• Use appropriate probe diameter and articulation: Many aviation-grade borescopes feature thin probes (often ~4 mm) with articulation and maneuverability to reach confined oil pathways, combustion chambers, or bearing housings.
• Illuminate thoroughly and use video/still capture: LED-equipped tips and bright lighting help reveal subtle discoloration, residue, or pooling — critical when spotting oil films or carbon deposits.
• Perform systematic, compartment-by-compartment inspection: Navigating through cylinders, combustion chambers, oil galleries, and bearing housings ensures no area is overlooked.
• Document and log findings: Storing images and video as part of the maintenance record supports trend analysis, future inspections, and evidence-based maintenance decisions.

These best practices transform borescope inspection from a quick check into a robust diagnostic method — one that can catch early oil leakage, residue buildup, or early-stage carbon deposit before they evolve into serious issues.

Real-World Impact: Aircraft Engines and Maintenance Efficiency

For aviation and helicopter maintenance professionals, employing borescope inspections to detect oil leaks or residue build-up offers multiple real-world benefits:

• Reduced downtime and maintenance cost: Avoiding full disassembly saves labor hours and reduces the need to remove or handle sensitive parts, which also lowers risk of introducing new faults.
• Improved safety and reliability: Detecting oil leaks before they cause overheating, bearing failure, or oil-related combustion issues dramatically improves operational safety and engine lifespan.
• Better documentation and traceability: Video or photo records give maintenance teams, operators, and auditors clear evidence of engine condition — critical for compliance, resale value, and long-term maintenance planning.
• Targeted maintenance and corrective action: Instead of replacement or full teardown, maintenance can focus only on implicated areas — seals, gaskets, oil lines, or combustion surfaces — minimizing parts cost and downtime.

In sectors beyond aviation — such as industrial turbines, power generation, or oil & gas machinery — the same principles apply: borescope inspections detect residue, leaks, corrosion, and wear in tight or inaccessible spaces, enabling safer, cost-effective maintenance.

Conclusion

Detecting oil leaks, carbon deposits, and residue build-up inside engines — especially aircraft and helicopter engines — is a critical part of preventative maintenance. Borescope technology empowers maintenance professionals with high-resolution, non-destructive visual access to internal engine compartments, enabling early detection of leaks or deposits that would otherwise remain hidden. By following best practices and capturing thorough visual documentation, borescope inspections contribute significantly to engine safety, efficiency, longevity, and maintenance cost savings.

USA Borescopes – Remote Visual Inspection Specialist

USA Borescopes provides a wide selection of industrial videoscopes, pipe cameras, rigid borescopes, intrinsically safe systems, and fiberscopes, with many units in stock and ready to ship. Aviation technicians can easily browse their complete range of inspection tools through the products catalog to find the ideal system for engine diagnostics.

They also offer borescope repair services for any make or model, including no-cost repair evaluations, along with borescope rentals anywhere in the continental U.S. If you need expert guidance or fast support, call now to contact their world-class team.

Author Bio:
Written by Carson J. McKnight, an aviation maintenance analyst with over 11 years’ experience in jet and helicopter engine inspections throughout North America. Carson specializes in remote visual inspection techniques, borescope diagnostics, and maintenance documentation practices that align with industry standards. Passionate about improving safety and reliability, Carson helps MRO teams adopt more precise, efficient inspection workflows — turning what used to be guesswork into verifiable, actionable data.