If you’ve been working on cars as long as me, you’ll remember the first timing belt you did and thought, “what was wrong with timing chains?” It was only a year ago, when I was working on a 2005 Audi A6 Quattro with a 3.2L engine with a broken timing chain tensioner and bent valves, that I started thinking, “what was wrong with timing belts?”
After years of timing belts, Audi and VW switched back to chains on some of their cars in 2005. For years, they had the timing belt turning one cam and a chain with a variable valve timing tensioner running the other cam. The 3.2L Audi engine has no less than four chains running the oil pump and keeping everything in time. We believe it’s a lack of maintenance, specifically oil changes, that’s causing some of the failures we’ve seen, so let’s take a look at what’s happening.
We aren’t sure why, but the failures we’ve seen all involve the right-side cylinder head. The tensioner will fail, allowing the chain to jump. The customer will complain of very poor running and lots of engine noise. The MIL will be lit and cam position codes will be stored. These six cylinders don’t run very well on just the left bank of cylinders and, depending on how many teeth the chain has jumped, the car may not run at all.
Upon inspection, we can find low to no compression in the right bank cylinders. Replacing the tensioner and repairing the head is not a difficult job, but it’s time-consuming and there are some special tools you’ll need to do the job (see Photo 1). You’ll need to quote a couple hours of diagnostic time to do a compression check and to pull the cam covers and verify that the cams are out of alignment.
We’ve done a half dozen of the 3.2L engines this year and fielded questions about rebuilt heads or installing used engines, and we found the most cost-effective way to repair these for the customer with the best return for us is to repair or rebuild the engine in-house. It’s basically doing a head gasket and lapping in some new valves, so let’s get started.