Originally Posted By: Hokiefyd
Originally Posted By: Gasbuggy
Originally Posted By: Alfred_B
165k on my Audi. The chains are not an issue on these cars, it's the chain tensioner. It's a hydraulic contraption powered by oil pressure. With time, it hardens and stops creating tension. When the chain jumps a tooth then BAM! bent valves.
Sounds like something Audi would make.
This is how most timing chain tensioners work: oil pressure. Many are ratcheted, to try to account for chain wear over time.
Some timing chain systems are very well designed, and some are not. I've owned a few of both, a Nissan KA24E being one of the worst, and a Cadillac Northstar being one of the best. You almost never hear of problems with a Northstar's timing chain system, but failures of Nissan's KA timing chains is well documented. Unfortunately, you rarely have this information up front...it takes years to manifest itself in the field.
I was under the impression that most tensioners are not hydraulic like the Audi, they are a spring driven worm and sector type set ups or simple spring loaded arms or plungers with ratchets to prevent push back. The majority are well designed and don't have a reputation for causing engine failure, like the Audi part.
I would not expect to hear about many Northstar chain issues because so many of those engines don't make it to a mileage that even a timing belt could handle.
Audi V8, can you spot the tensioners?
And a very comparable Ford 4.6 DOHC V8 from the Mark VIII and Cobras