Engine Rattles Upon Startup

[fnkmstr67]

My 2000 GMC Sierra has just over 100,000 miles. After letting it sit overnight, the engine rattles when I start it. Sounds like it is low on oil, but it isn't. The noise goes away after a minute or so. Could it be the lifters not getting oil? The oil pressuer guage says plnty of pressure. Should I be worried? The truck seems to run just fine, no smoke from the exhuast. Should I try a synthetic oil? Kinda worries me.....

[alwcurlz]

My 2000 GMC Sierra has just over 100,000 miles. After letting it sit overnight, the engine rattles when I start it. Sounds like it is low on oil, but it isn't. The noise goes away after a minute or so. Could it be the lifters not getting oil? The oil pressuer guage says plnty of pressure. Should I be worried? The truck seems to run just fine, no smoke from the exhuast. Should I try a synthetic oil? Kinda worries me.....

 

Well, what you are hearing is called a "cylinder slap". Sounds like an engine knock similar to a diesel. As I've been informed, when the engine is cold, there is excess play between the bottom of the piston sleeves and cylinder walls. There isn't any damage being caused going on that I've heard about but, sure sounds like there would be. Mine makes that sound when first starting up as well as my brother's truck. It's plagued the 5.3 engines since they were introduced back in 1999. GM states there isn't any adverse affect from this as far as engine failures. I have 136,000 miles on mine, 198,000 on my brother's truck. We both use Mobil 1 just because we like the idea of a better running, cleaner engine. Many other makers such as Ford and Dodge have similar issues like that with much less miles on them. I have been just letting my engine idle for about 20-30 seconds till the engine warms up as the sound will go away. The noise heard from our engines is only present when starting them at temps below 60°. My brother's 5.3 with 198,000 miles runs just as good as mine with 135,000. I've seen them go way over 200,000 miles so I'm happy to just let it warm up for a bit before taking off. In much colder temps it may be necessary to idle longer to alleviate the sound.