Small puddle under my 2006 C2S with 70K miles in the rear left area earlier this week. It's coolant - pink & sticky to the touch. The coolant in the overflow tank was about 1" below the min line.

Drove it home watching gauges, no temps spikes in coolant or oil. Parked overnight, no drips.

Next day top off the coolant and drive it around. After parking and sitting for a while a puddle appears again. Coolant drops in the overflow tank to about the same level. You can smell the sweet coolant on hot metal burning too.

The local speed shop here diagnosed it as a cracked coolant overflow tank. I'm going for the complete coolant repair/upgrade path while they are in there - 3rd radiator install, water pump upgrade to the latest OEM version with the metal impeller, thermostat replacement and a new overflow tank. They are lowering the engine to do much of the work. New battery harness, spark plugs and serpentine belt at the same time while access is easier.

All this was on my ToDo list anyway. I guess Murphy chose to have the work done now instead of on my schedule. The good news is she will be ready for pickup before the long weekend!

 

Cracked overflow tank

Here's a photo of the 3rd radiator after install. The work was done by IMOLA motorsports in Golden Valley, MN






And from the rear