My 2003 Jeep Liberty heater is blowing cold air when idling. Warms up when you hit the accelerator. I also hear a water rolling sound upon take off after idling. Water pump? Heater Core?

how do I check the water level how do I check the water level

Open the radiator cap...when it is not hot. The radiator, this at the very front of the engine and has two electric fans attached to it on the engine side covered by a shroud. Take the radiator cap off and check the antifreeze level. If it is low, add water or antifreeze. Once you top it off, close the radiator cap and follow the little black hose over to the coolant resevoir. There is a line on this resevoir indicating the proper level of coolant with the engine hot and cold. Since you are checking it when it is not hot, fill it to the proper level. If this isn't the problem let me know and we'll go to step 2. Also, check to see if the temperature gauge on the dashboard goes up near the 12 oclock postition or does it stay down at the 8 and 9 postition. Open the radiator cap...when it is not hot. The radiator, this at the very front of the engine and has two electric fans attached to it on the engine side covered by a shroud. Take the radiator cap off and check the antifreeze level. If it is low, add water or antifreeze. Once you top it off, close the radiator cap and follow the little black hose over to the coolant resevoir. There is a line on this resevoir indicating the proper level of coolant with the engine hot and cold. Since you are checking it when it is not hot, fill it to the proper level. If this isn't the problem let me know and we'll go to step 2. Also, check to see if the temperature gauge on the dashboard goes up near the 12 oclock postition or does it stay down at the 8 and 9 postition.