losing coolant??

[jaygss]

I have a 2005 silverado 4x4 with a 5.3 and last week I noticed that the coolant resivoir was low so I added some coolant and went about my buisness. Then 2 days after that the check engine light came on? the truck still runs fine no leaking on the ground, not in the oil, level has not changed, can't smell it in the exhaust. I looked all over the engine and can't find any evidence that it's leaking. do these trucks have any common problems that would explain this? any help would be appreciated.thanks

[GasGuzzler]

SES light should not be related unless it's low enough to either set P0128 or put it in REP.

Water pump to block gaskets are very common. They usually only leak cold and do not generally leak enough to make a puddle because there are so many places for the coolant to settle on the way to the floor. Once the engine heats up the wetness evaporates. Check the conduit on the harness under the balancer after it has sat all night.

[05z71]

mine did that and it was the actual water pump leaking out of a seal if I remember right. my stealership service guy told me it was a common problem and swapped it for me even though I was a little out of warrenty.