[DSGT]

In have seen a lot of weird things in my 40 + years of dealing with cars, but this has to be among the most bizarre symptoms ever .. waiting for someone with solid mechanical experience to chime in and post a diagnosis, I'd be very interested in what causes that ..:|

Unless it's the dipstick top or stem rattling against the tube ( when the engine is cold it vibrates a bit more ) but there's no way it would make that kind of sound, IMO.

 

[DSGT]

I'll give it a shot. All modern engines use a PCV system that generally requires the engine be sealed up with no air leaks, etc. When you pull out the oil dip stick, the engine is no longer "air tight" and anything that is related to the PCV / vacuum system will be affected, such as vacuum pumps...etc...maybe check those...

Sounds like a pretty solid theory to me ! :thumbsup:
And that can be tested when starting our cars cold , just pull out the dipsrick and see if the engine makes a comparable noise . I can try that tomorrow but if someone manages to beat me to it before then, please post . :smile2:

 

[DSGT]

Started the car today, pulled out the oil dipstick within the first 10 seconds of idle just to see if there was any sound - there was none - but since the OP indicated this was happening only at operating temperature after I drove the car for about 15 minutes to a grocery store ( should have been plenty of time for the engine to reach full warm up ), I pulled out the dipstick once again, but still no unusual sounds were present.