My 05 LT sound like water sloshing around under the dash, usually when engine is cold. Antifreeze reservoir keeps getting low. I think air is getting in system and I hear antifreeze moving in heater core. No puddles under car and no leaks I can see. Anyone else have this problem?

 

That your Antifreeze Reservoir keeps getting low would have me worried about an Internal Leak. Run a Cooling System Pressure Check. I think AutoZone has the Tool and will loan it out for a Credit Card Deposit or your Driver License.

Put the Tool on the Radiator Fill Neck. Pump-up the Pressure to the "Working Pressure" of the System and watch the Gauge while looking-around for leaks. If the Pressure falls-off your System is compromised somewhere and needs to get fixed.

Sometimes you get lucky and find an External Fitting or Fastener loose and that the end of it. But, the down-side is getting Coolant in the Crankcase. No good.
Look on the Inside of your Radiator Cap, Oil Filler Cap ... or, ... Pull the Front Valve Cover and look for "Slime".
If you got "Slime" ... you got a problem!

 

well if ur coolant tank is constantly getting low then u have to get that checked out...like right NOW!

 

Thanks for the replys. Had the oil changed, they said it looked fine. No slime found anywhere. Only 35000 miles. Its 50 degrees out, might go poke around under the hood for awhile, see if i see any small leaks.

 

have u been adding coolant all along?

 

I bought the car last Feb and only topped it off once. Maybe a quart. this time i just added little less than 2 quarts. I read the manual and it says if you have to add fluid more than 4 times a year get it check. Once concerns me.

 

well if u only have to add once a year i wouldnt b that concerned...if your coolant seperates into water and antifreeze and u heat up the system then the water will evap...however very little of the coolant seperates and that is y u may have to add coolant periodically. This is a natural occcurance and happens to everyone. That is one of the reasons u should have ur coolant checked at every oil change, first off for a major leak and second to check for excessive evaporation

 

OH SNAPS!! I ALSO have an '05 LT, and I ALSO have this problem. I just thought it was normal for the car. Never had an issue with coolant leaking. Almost 50,000 miles now. Seems to "Flush" whenever you hit the gas. After it warms up, usually goes away.