What causes Audi S4 oil leaks?
Many Audi S4's have a rough service history. We consider 'rough' to be irregular oil changes, extreme hot or cold climates, a lot of short driving where full engine temperature is never reached, and excessive low RPM city driving. This produces a great deal of condensation and moisture to form within the engine, causing a build up of sludge. Many owners have bought an Audi S4 without knowing the oil change and driving history. If you own or have bought an Audi S4 with over a 100,000 miles that has oil leaks, the crankcase breather system should be treated as suspect. If you remove the valve cover and see a lot of resinous accumulation in the valve train area, this indicates that the vehicle already has heavy amounts of oil sludge build up throughout the engine. Suspect number one is the Audi S4 crankcase breather system.
Years of rough service history as mentioned above, cause contamination to take place inside the engine which clogs the Audi S4 crankcase breather hose system. Due to this blockage, the air flow generated within the engine crankcase is restricted and will not allow the system to breath properly. When the engine is running, pressure builds up in the crankcase and causes oil to push out and leak from the weakest parts of the engine.