Sorry for the multiple threads but I wanted to list what's been happening more clearly. 03 MCS 162K miles .
About 2 weeks ago started having valve train chatter along with a slight miss . Once the chatter stopped the miss stopped as well . Sometimes cold start sometimes warm start . It was hit and miss . Good for 2 days then started again . I replaced the timing chain tensioner but it persisted intermittently.

Twice while sitting in traffic the temp needle suddenly pegged to the highest reading but no evidence of overheating . No smoke no fan no intense heat . Restarted the car and temp read normal . Turns out coolant was very low . Filled it and a few days latter happened again same issue.coolant very low. No coolant leaks I could find and no white smoke from the exhaust. I'm thinking it showed overheat because there was a void of coolant by the temp sensor

Today I found the oil cap has milkshake oil under it but oil in pan and dip stick look normal .
Car runs normally and strongly . I pulled the oil cap while it's running on a cold start and have a pretty strong positive pressure

I'm assuming these two issues are related
I don't understand why oil in pan looks normal with the amount of water that's disappearing
and I'm not sure how to proceed
I've read that the oil cooler can be an issue
Any help GREATLY appreciated

 

There are kits you can buy to test for exhaust gases in your coolant (head gasket)

autozone has a free presure tester (cooling system)

frequent short trips can cause condensation in the valve cover, I’m told…