We saved this customer from what could be a very expensive repair, a broken timing belt. Like most cars now on the road, the Audi 2.7 and 2.8 engines use a rubber timing belt. Located in a plastic housing on the front of the engine, the timing belt keeps the valve opening in sequence with the rotation of the engine pistons. A failure of the timing will allow the valves to contact the pistons, resulting in major engine damage.
The Audi and VW 1.8, 2.7 and 2.8 liter engines also use a timing chain to drive the secondary camshafts. This chain is kept in proper tension by tensioners fed from the engine oil. Over time, many tens of thousands of miles, the seals which serve to seal the tensioners to the cylinder head start to leak, note the image below. As a rule we always replace then when serving the timing belt, but sometimes they don’t make it that far. Our goal, when doing a timing belt service, is make the work last another 100,000 miles.
The oil resulting from these seal leaks can find its way into the front engine timing cover, and onto the timing belt. The timing belt, being made of rubber, deteriorates with time and can fail without warning, resulting in catastrophic engine damage. Thankfully this was caught by one of our observant techs before failure occurred.