A burning oil smell from under your 2019 GMC Sierra's hood indicates oil is leaking and contacting hot engine or exhaust components. This issue is common on the 5.3L and 6.2L V8 engines and requires identification of the leak source to prevent engine damage and fire hazards.
Why Oil Burns Under the Hood
When engine oil escapes from seals or gaskets, it runs down the engine until it reaches hot surfaces. The exhaust manifolds are hot enough to vaporize oil on contact, creating the characteristic burning smell. The smoke and smell are often more noticeable at idle when there's no airflow to disperse them.
Common Leak Sources on Sierra V8s
The 5.3L and 6.2L engines have several known leak points: valve cover gaskets seeping onto exhaust manifolds, oil pressure sensor leaks, oil pan gaskets especially at rear, active fuel management (AFM) lifter oil leaks, and timing cover seals. Front and rear main seals can also develop leaks on higher-mileage trucks.
AFM System Considerations
Sierras with Active Fuel Management can develop oil leaks related to the AFM lifter system. The AFM lifters require pressurized oil and leaks in this system can cause burning smell. Some owners have experienced relief by deactivating AFM, though this doesn't repair existing leaks.
Identifying the Leak
Clean the engine with degreaser to remove existing oil residue. Add UV dye to the engine oil. Run the engine and use a UV light to trace the fluorescent dye from its source. Note whether oil appears on one side or both sides of the engine to narrow down valve cover versus lower engine leaks.
Repair Priority
While small seepage can be monitored, significant oil burning creates fire risk and smoke. Oil dripping onto hot exhaust manifolds can ignite under certain conditions. Additionally, continued oil loss leads to low oil level and potential engine damage. Repair leaks promptly for safety and engine protection.