I have a completely stock 2006 MCS that has made a valve type of noise on start up for over a year now. The problem only occurs after the car has been sitting for a while (overnight). The car has been brought to the dealer many times for this issue and they state that nothing is wrong. Lately the noise is accompanied by the oil light staying on for a few seconds during start up. I have noticed that if the car has not been used for a few days the noise will be louder and the oil light will stay on longer when the car is started. Note I have checked the oil and it is at the correct level. Any help that anyone can provide would be greatly appreciated.

 

The dealer might be saying nothing is wrong because they can't replicate the problem unless you let the car sit at least overnight. Have you done this?

It is not unusual for there to be a bit of valve train / timing chain rattle on startup when cold, but it should not last more than 1-2 seconds at most. Even in this case, I don't recall the oil light being lit.


If it is rattling for more than 2-3 seconds, there might a problem with the oil delivery system. Either the oil pump, oil sump pickup tube, oil filter, or oil pressure regulator. We know it is not an electrical issue because the car is showing symptoms of oil starvation, at least on startup.

 

How many miles on the motor?
what is the oil? 5w30? You might try a 0w30 to speed up the pumping of the oil to the topend on start...
Sounds like true mechanical engine issue...like a failing oil pump...should be fixed asap. A good shop can take the valve cover off...check for dammage from lack oil oil....and maybe suggest the next step...maybe inspecting the filter/etc before digging deeper.

 

My 2003 MCS does this and it is actually in the shop getting a new oil pressure switch right now, thats what they said it needed. They told me it should take away the weird sound on start up. I don't know if this will help you out but i thought your situation sounded familiar.