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Probably not the chain Posted by Ari [Email] ![]() ![]() In Reply to: Question About Timing Chain Rattle, Peter Ingram, Thu, 22 Jan 2004 10:00:16 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The engine uses hydraulic valve lifters, and those require oil pressure to pump up and run. So it's not unusual for the engine to rattle - not from a chain, but from the hydraulic lifters. Due to the way oil gets ported around the lifters, it always seems to me that the lifters at the highest portion of the engine - coincidentially the side right by the chain - get oil last. Not only are the lifters rattly, but the valve timing is a bit off, adding to the noise.
I consider some rattle at cold startup, that goes away after a minute or so, as normal. Quite often it gets a little better with thinner oil than with heavier oil, because the thinner oil gets pumping faster. That's not only good for the valves, but the rest of the engine.
If the noise only occurs when the engine is first started cold, and goes away, I wouldn't worry. As they like to say "they all do it". Or at least most do. If the noise continues after the engine is warm, then it's time to keep looking. But there are a lot of things that can cause an engine rattle. A noisy fuel injector, a weak fuel rail damper, even a sympathetic vibration from a bracket somewhere. at a specific idle speed. The engine tends to idle just a hair faster when cold, and something may be vibrating.
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