yellow oil in overflow tank

What is the behavior of the engine? is it overheating? is it loosing oil? Is it loosing coolant? checked the transmission fluid level lately?.....mmmm...yellow oil? are you sure that it is oil, and not disintegrated glycol? there is nothing YELLOW in the system must be a product of a system depositing into the coolant system~....thinking....thinking oil fumes could be yellow, Dexcool is a yellow coolant.....been drinkin' a lot of lemonade lately?

lol, good answer, have your manifilod pressure checked, your car is still under warenty, prop blown the head gasket

Oil in coolant is never a good thing. Unless motor oil was accidentally added to the reservoir, it's presence is serious. In view of the extended drivetrain warranty, I agree a quick trip to the dealer is in order,

I took the car back, and during manufacturing of the radiator, the flux was not fully removed. They had to replace the overflow tank, and flush 3 times. Covered under warranty. Thank's all.

wow...that totally makes sense....and now I have another magic trick to pull out of my hat...thanks for this~