mike@fmc

Recently I drove the 95 A6 through a large puddle, and on the way home the car sent up a bit of steam from under the hood... at first I thought it was water from the puddle, but at home realized it was coolant. Now I can't drive it much more than around the block, before I arrive home and the coolant has a heartbeat. Coolant reservoir (hot) is nearly full, and the hose connected to the top of the radiator is hot and pulsates. Coolant hose connected to the bottom of the radiator is warm - I am wondering, is this a bad thermostat, or are my heads leaking? I also noticed a bit of water coming from my tailpipes; i am a bit worried.

A6Gary

Most probably a closed stuck thermostat. If its plain water out the tailpipe rather than colored coolant, then that is most likely just condensation from a not–fully–warmed–up engine.

Asizzle

a6gary is right..could be stuck thermostat...could also be clogged radiator ..start the car..allow it to warm up...monitor temp gauge make sure it does not overheat so it does not ruin your cylinder head / head gasket,,check for coolant spill..fix as needed..other than that..make sure the seal on the reservoir bottle is intact
secondly...try bleeding the system..you might have an air pocket somewhere...if all else fails,,have the system pressure checked for leaks..if no leaks,,as a6gary said,,,it might just be the thermostat,,,keep me posted,,goodluck

One

Im leaning toward a clogged radiator or partially clogged/stuck thermostat. If it was fully stuck you would not have any circulation to the radiator atall. The coolant runs from the block through the thermostat to the top radiator hose, down to the bottom hose, back to the engine.
Take out your thermostat, refill coolant, run engine to see if it still overheats, if not, replace, t-stat. If yes, take a closer look at your radiator.

upallnight

A quick way to determine if you have a blown head gasket is to pressurize the cooling system. Most radiator shops can do this for you. If the system holds pressure then you don't have a blown head gasket.