C63 2010 Start Up Rattle... Split Second Then Gone...

[horsesuitedfool]

Hi, as the title says, I have a C63 rattle when I first crank the engine in the morning, it goes away almost instantaneously and it is worse when the oil level was lower than at the full mark and also worse when I had OW40 oil.... These things make me believe its down to oil pressure perhaps not being maintained at the top of the engine or on a tensioner or something as it goes away as soon as oil pressure is achieved, but I am not sure. Anyone have any ideas on what it could be?

 

[PobodY]

I think you've already nailed it. - It's oil pressure; when there's less in the sump, or it's a thinner grade, it takes a bit longer to get all the way to the top of the engine.

It's quite a common thing and I wouldn't have thought it's any cause for concern; just start it and wait for the noise to stop before you put any load on it.