Gunk is the thick, greasy residue that builds up on the outside of an engine or inside neglected fluid passages. It forms when leaking oil or coolant mixes with road dust and bakes in the heat of the engine bay. Mechanics have to scrape or dissolve this sludge before they can accurately diagnose leaks or disassemble parts.
Heard on the job
Grab the parts washer brush, there's half an inch of gunk covering the timing cover bolts.
Also heard as
- sludge
- grime
Related terms
Blow-by
Combustion gases that escape past the piston rings and enter the engine crankcase.
PCV
This emissions control system routes blow-by gases from the crankcase back into the intake manifold.
Oil change
The routine maintenance process of draining degraded engine lubricant and replacing it with fresh fluid.