Every 30 days or 1000 miles my coolant disappears I don't see a leak under the car.

Has the radiator cap been replaced? try that first.

check sump oil color
If grey that is coolant into the sump , probably from behind the water pump impeller
because water loss is not evident the fact that there is loss means that there is a leak some where
There is a drain hole under the water pump housing and if the seal is gone the water will leak out there under pressure and when operating and the coolant is lost in the air stream
Take it to an accredited radiator shop and have the system pressure tested

Have your coolant cap checked. If it is bad it won't hold pressure and it will allow coolant to leak out.

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Upper hose or lower hose loose or check ythe headgaskeck leak maybe

Hi Heather,it may be your water pump leaking or a radiator hose.Keep water in it,keep a jug in the vehicle,if it's the water pump,then it will leak when it is parked,keep the over flow container full.

Unless the pump is leaking i don't recommend you spend the money, but it my bet they saw coolant stains at the shaft seal, and since a coolant leak can lead to overheating the engine the pump should be replaced any time it shows signs of leaking. A new water pump is much cheaper than a new engine by $1000's. You can do this yourself, it is very easy to replace.

Check for water laying in the heater core box.Most likely the heater core is leaking.

first of all, was the water on the passenger side from the air conditioner or a leak (what color was the fluid?)-the cap has to be tight, otherwise it will not hold pressure, so that has to be checked before you set off again-push down as you turn the cap clockwise, and it will not hurt to have water in the system (it actually transfers heat better than antifreeze) but it has a much lower boiling point, so the cap has to be tight. Pay attention to the temperature gauge and do NOT overheat it-it is an aluminum engine and they do not tolerate excessive heat. Take your time, no AC (although the AC being on can keep a good cooling system more stable since the radiator fan is forced on when the AC is running, so you can, within reason, experiment)-no matter what, just don't let it run hot-not worth it.

if it was a head gasket it would overheat long before 20-30 miles if there is no sign of water leaking from hoses etc when the car has warmed up it is most probably the radiator or possibly the water pump or thermostat has called it a day

Take it to a mechanic and ask for a coolant leak test, they attach a unit to the header tank which will detect anything that may indicate the head gasket is leaking. Should not cost more that a few dollars.
Cruise control issue is not related to the coolant loss, have them do a code check on the vehicle too.