Hi. I have a 2003 Mazda 6 Luxury Sports Hatch, 2.3L 4 cyl manual - 158,000Km. In the past few months, I have noticed a rattle from the front (apparently RHS) of the engine, especially at low speed/acceleration. The car has been serviced regularly by the dealer since new. After a couple of very disappointing services, I have now moved to a private mechanic who can't pinpoint the problem but is certain it is internal in the engine. He has suggested timing chain and I see from several forums this is probably likely. My concern is whether I should get it replaced sooner rather than later. The mechanic suggested waiting to see how if it gets any worse. What is the likelihood of the chain breaking? And consequences? I haven't been game to ask the mechanic for a quote yet! How much should I expect to pay for replacement (parts & labour) in Australia? Appreciate any guidance you can offer.
Hello and welcome to JustAnswer!
If the noise is coming from the timing cover area at the front of the engine then I agree, it's likely coming from the timing chain. The timing chain has two guides and a hydraulic tensioner which presses on one of the guides to tension the chain. If the chain has stretched to the point where the tensioner can no longer keep it tight, a guide is damaged, or the tensioner has failed then it will cause the chain to slap the guide. This will cause almost a knock type noise at the front of the engine.
I would recommend having it replaced sooner rather than later. If the chain ends up breaking then you could do expensive internal engine damage.
Replacing the chain calls for right at 5 hours of labor and you'll have about $300 in parts; I would recommend replacing the guides and tensioner at the same time as the chain.
I do work for a Chrysler dealer so naturally my experience is mostly with Chrysler, Dodge and Jeep products, but we work on all brands, and I have service information for all vehicles. Your question had been up for an extended time without a response so I wanted to try to help even though I do not work at a Mazda dealer.