Thanks Nate, is complete refresh meaning doing a radiator flush and refill?

A complete refresh is replacing any parts with over 60,000 miles on them and draining the fluid. ECS tuning sells a great package, and if your tracking down the leak it is worthwhile to order the stage 3 (or most inclusive) package. A lot of parts look "fine" until you take them out and compare the condition. If you think a part is in good condition enough to reuse, then you can put it back on knowing you have a spare in hands reach!

The headaches saved will be worth the extra 2-300 bucks in parts. I've chased after my leak as follows: thermostat (was leaking), upper rad hose (separated from housing), expansion tank/ cap, water pump (bad gasket/ bearing on the way out), lower hose/ fan switch o ring, and finally the radiator (hairline crack on plastic end tank.

That meant taking out the fan, taking off belts, multiple coolant refills/ bleeds, worrying, cursing... You get the picture.

And I wasn't paying for labor! I couldn't even imagine!!

Thermostat going bad is not uncommon.

Also, since you have the system open, replace your coolant expansion tank while you are at it. They go bad anytime after 60k miles. Good time to check your belts, hoses, idler pulleys, etc. while you are messing around in that area.

Good luck!

Thank you Nate! I'm already cursing by knowing what I need to do!!!

To those that have a leak--have a system pressure test done to find the leak. If it still doesn't show look for other symptoms like some sweet smelling white smoke out the tailpipe. Most common leak sources and easiest to eliminate are coolant hoses or heater hoses, plastic piece on top of the expansion tank or the tank itself. It could be a Vanos cover leak. That is harder to pinpoint but one strong indication is coolant leaking from the bellhousing.

For those showing a code and don't have a leak, easiest, cheapest and most common potential fix is to replace the thermostat as several have mentioned. I would do that first.

Unless the engine has run hot for an extended period time you may never have to replace some of the parts in the cooling system.