What causes Audi A4 oil leaks?

Many Audi A4'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 A4 without knowing the oil change and driving history. If you own or have bought an Audi A4 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 A4 crankcase breather system. CLICK HERE, for our detailed and illustrated Audi A4 Crankcase Breather Hose System page. It explains how this buildup happens and how to fix it.

Years of rough service history as mentioned above, cause contamination to take place inside the engine which clogs the Audi A4 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.

CLICK HERE, for our detailed and illustrated Audi A4 Crankcase Breather Hose System page.

Audi A4 Oil Leaks #1 - Cam Chain Tensioner Gaskets and Seals

CLICK HERE for our detailed and illustrated page that focuses on Audi valve cover gasket leaks. » Including replacement VIDEOS «

When the Audi A4 camshaft adjuster seals and valve cover gaskets leak they typically cause a burning oil smell. The passenger side cam chain tensioner seal is located on the backside of the cylinder head and will drip oil onto the down pipe causing this smell. This Audi A4 leak is best seen through the passenger side wheel well as pictured (Image 1). The driver side cam chain tensioner seals will leak down onto the A/C compressor and oil filter area (Image 2).

Audi A4 Oil Leaks #2 - Valve Cover Gaskets

When the Audi A4 valve cover gaskets are leaking you will get a leak along the entire outer edge of the valve cover, which then begins to leak down onto the exhaust manifold. There will also be significant leaking into the spark plug chambers of the cylinder head (Image 3).

Audi A4 Oil Leaks #3 - Camshaft Seals and Plugs

When the Audi A4 camshaft seals are leaking you'll find oil down the front side of the engine. There is usually an oil trail between the seam of the timing belt backing cover and the cylinder head. This oil trail continues down onto the underside of the oil pan making it easy to determine a leaking passenger side camshaft plug and seals (Image 4). The drivers side camshaft plugs and seals can be much harder to pinpoint. This is because the symptoms are similar to those of leaking cam chain tensioner gaskets. Typically the driver side cam seals leak down onto the A/C compressor and oil filter area, similar to a leaking cam chain tensioner gasket. The best way to diagnose the leak on the driver side cam seal is to laterally look and see if it's leaking.

Audi A4 Oil Leaks #4 - Front and Rear Crankshaft Seals

When the Audi A4 front crankshaft seal is leaking you will see a trail of oil down the front and side of the oil pan. This is many times misdiagnosed as a leaking Audi A4 oil pan gasket (Image 5). The rear Audi A4 crankshaft seal will cause a collection of oil to accumulate and drip from the bottom of the bell housing area (Image 6).

Crankshaft seals are made of very reliable materials and as a rule don't fail. The root cause for their failure is almost always due to a blocked crankcase breather hose system. With a clogged system, crankcase pressure with in the engine is not released. This pressure along with the engine oil is then driven out of the crankcase past these front and rear seals.