2012 Elantra 1.8 Rattle from top area of engine on cold
2012 Elantra 1.8 Rattle from top area of engine on cold starts, intermittent but often. Lasts 2 or 3 seconds. No other symptoms & had flawless oil changes every 5k. 105k on now. Other reports of this but unknown cause?
This is a pretty common issue on a lot of newer cars with Variable valve timing that is controlled by the camshaft gears that move. What happens is there is a solenoid that is controlled by the ECU, to either allow oil pressure to the camshaft gear or removed oil. Buy doing this it can advance or retard the timing of the engine. Ill attach a picture of a cut away of the gear. After some wear the camshaft gear is no longer able to hold oil pressure inside the gear, so all the oil drains out and when you start the car the rattle you are hearing is the camshaft gearing going to its max limit in either direction and bottoming out, then after a few seconds of the engine running oil pressure is built up and the noise goes away. I Have replaced 100's of gears for this exact issue over the years on just about all makes and models of cars. If it gets bad enough it will set a check engine light and adjustment of the gear will not be able to change while the engine is running, at that point it needs to be taken care of. This noise should be covered under powertain warranty also. Might be worth a call to the dealer and see if its covered.
I really hope this helps,