my s2k has been making a weird noise long story short i took it to the dealership for the free oil change drove it for a week or 2 and smelt oil lifted the hood to find no oil cap oil was above the low oil line and i say 1.25 quarts low, no oil light ever came on , i added a quart of oil brought to proper level and have hear the nose in the attached video since. I cleaned the throttle body , cleaned the idle air control and added some injector cleaner to my fuel tank, there is NO check engine light on. I think it sounds like a valve issue or an intake manifold leak, any ideas??????here is the video My link

 

You say no Oil cap was found when you opened the hood? Was the car making the noise before you found the oil cap was missing? My best guess is maybe the oil cap got stuck somewhere beneath and is making that noise??? Or maybe some debris got inside of your engine? Either way, good luck, I hope you find whats going on with your car. Let us know when resolve the issue, just in case anyone else is having a similar problem

 

I bet the dealership didn't screw the oil cap on tightly. It probably twisted off and fell behind your engine. I would get under your car and see if the oil cap is there. Nothing really happens if you drive the car without an oil cap, except that oil will escape and dirty your engine.

If the oil is above the L mark your about 1qt low; most likely, your not yet in the danger zone of toasting your engine.

I would assume that an intake leak would cause your idle to fluctuate and valve issues would throw a misfire light.

Try and find that oil cap and check back with us.

 

Oil cap is stuck between the trans and firewall, and that is your noise.

Go back to the dealer and document their typical incompetence.

 

Don't be so hard on the dealer, their electricity costs alone are around $10,000 a month. It's not their fault that their business model has them hiring people that have trouble tying their shoes let alone working on cars and paying them a pittance on top. They need to do that just so they can break even by charging $140/h for labor..

 

...and its a good chance they used the wrong oil filter. Check that asap.