Timing Chain Kits: What's Inside a 16-Piece Audi 3.0 V6 Kit, and Why Chains Aren't 'Lifetime'

Chains Came First, Belts Won, Then Chains Came Back

The camshaft has to turn at exactly half crankshaft speed, forever, or the valves and the pistons try to occupy the same address. For the first sixty years of the automobile, engineers solved that with gears and chains, because those were the things that existed. Then in 1962 a small German firm called Glas put a rubber toothed belt on a production car's camshaft, and in 1966 Pontiac did it on its overhead-cam six for the American market. Belts were quieter, cheaper, lighter and easier to route — and they had one enormous catch, which was that they aged out and snapped, and on an interference engine a snapped belt bends every valve it touches.

So the industry swung back. By the 2000s marketing departments had discovered that a chain could be printed on the brochure as "lifetime" while a belt meant a $900 service bill at 90,000 miles. Owners loved it. What the brochures did not mention is that a chain drive is not one part. It is a chain, two or three sprockets, plastic-faced guides, spring-and-oil-pressure tensioners, and bolts — and the plastic and the tensioners are absolutely not lifetime parts.

What Is Actually in a Full Kit

Look at the part count. We have an A-Premium 16-piece engine timing chain kit for the Audi 3.0 V6 — Q5, Q7, A6, A7, A8, S4, S5, SQ5 — marked down to $89.99 from $179.99. Sixteen pieces, for one engine's timing drive. That number tells you everything about why "just replace the chain" is not a real job.

A complete kit generally covers the chains themselves, the sprockets they ride on, the tensioners that take up slack, and the guides and rails the chain slides against. The guides are where the story usually ends: they are steel or aluminum backing with a plastic wear face, and after a decade of heat cycles and oil the plastic gets brittle, cracks, and starts shedding pieces into the pan. Once a guide breaks, the chain goes slack, the tensioner runs out of travel, and the cam timing walks away from where it is supposed to be. That is why kits are sold as kits. Replacing a stretched chain while leaving twelve-year-old guides in place is buying yourself the same repair twice.

The Other Two on the Shelf

The GM 2.4L Ecotec and the Hyundai/Kia Theta family are both engines where this is a well-known job rather than an exotic one:

• An engine timing chain kit with water pump sprocket for the 2011-2017 Chevy Equinox and Captiva 2.4L — $142.19. The included water pump sprocket matters: on this engine layout the pump is driven off the timing side, so the pump is either already exposed or already in the way once you are in there.
• A timing chain kit for the 2.0L and 2.4L Hyundai Sonata, Santa Fe and Tucson and the Kia Optima and Sorento — $98.09.

And while the front of the engine is open: an electric engine water pump for the BMW N52 3.0L inline-six, replacing OE part 11517632426, at $62.99 from $89.99. Different engine family, same principle — the N52's electric pump is a known wear item, and nobody has ever regretted replacing a water pump that was already accessible.

How to Tell Before It's Expensive

Chains give warning. Belts mostly do not. Learn the warnings:

• A rattle on cold start that lasts a second or two and then goes quiet. This is the classic one. Oil pressure has not yet filled the tensioner, the slack chain slaps the guide, and it quiets down once pressure comes up. As the guides wear, that second becomes three seconds, then it stops going away.
• Cam/crank correlation codes. P0016, P0017 and their relatives mean the computer has measured the cam and crank sensors disagreeing about where they should be. That is timing that has physically moved.
• Plastic in the oil pan or on the drain plug magnet. Guides only shed once.
• A rough idle or a stumble that appears with no other explanation on an engine with variable valve timing, because the VVT phasers rely on the chain being where it should be.

One more thing, and it is the cheapest advice in this article: chains die from oil, not from mileage. Extended oil change intervals, the wrong viscosity, or a car that has spent its life doing eight-minute trips will destroy a timing drive long before the odometer says it should. If you are buying a used car with a chain engine, service records are the actual inspection.

While You're In There

A timing job puts the accessory drive in your hands anyway, so it is a reasonable moment to deal with anything else spinning off the front of the engine. We have an OCPTY 150-amp alternator for the Land Rover LR3 and Range Rover Sport 4.2L and 4.4L V8, unit 11206, at $146.99 — not part of the timing drive, but exactly the kind of part people wish they had swapped while the belt was already off.