Oil Coolers Repair & Overhaul

Oil coolers are heat exchangers dedicated to managing the temperature of engine and accessory lubricating oil, removing the heat that oil picks up as it lubricates and cools bearings, gears, and other rotating components. Depending on the design, they reject that heat either to ambient or fan air in an air-cooled oil cooler, or to the fuel stream in a fuel/oil heat exchanger, which doubles as a means of warming fuel. The component class includes Oil Coolers, Air to Oil Coolers, Air Cooled Oil Coolers, and Fuel/Oil and Oil to Fuel Heat Exchangers serving both engine and airframe systems.

These units are typically brazed plate-fin or tube-and-shell cores in aluminum or stainless-steel alloys, designed to keep oil within its operating temperature band across a wide range of power settings. Because oil coolers run continuously and see both high oil pressures and contaminants, they are subject to a familiar set of degradation modes: internal leakage between the oil and air or fuel circuits, external seepage at joints, fouling and varnish buildup that restricts flow, and thermal-fatigue cracking from repeated heating and cooling. Cross-circuit leakage is particularly serious because it can contaminate fuel with oil or starve the cooler of flow. Overhaul by a qualified repair station restores circuit separation, flow, and cooling performance, recovering a high-value component rather than scrapping it.

QTC's oil cooler overhaul begins with incoming inspection and configuration verification, after which the unit is cleaned to remove oil varnish, sludge, fouling, and corrosion from both the oil side and the air or fuel side of the core. The cleaned cooler is inspected visually and dimensionally and evaluated with non-destructive techniques to detect cracks, internal cross-circuit leakage, and braze-joint defects that compromise separation between the fluid circuits.

Leaks and damaged core elements, headers, and fittings are repaired using methods suited to the unit's construction, and restricted passages are cleared to restore oil flow and heat rejection. Each unit is then leak- and pressure-tested on both circuits and functionally verified against the applicable specification to confirm that the oil and air or fuel streams are fully isolated and that cooling performance is within limits. Once all acceptance criteria are met, QTC completes the required documentation and returns the oil cooler to service with airworthiness certification under its Part 145 approvals.