allproper

when i purchase the vehicle,after driving for about 30 min...i start feeling a presure buildup on the line under the car..it will give me a hitting sound under my seat...like if something is hitting the bottom of the car..only wen the car gets hot...about a month later the sound got louder..then stop completely...2 min later the abc light came on and the car drop complete...so i drove it slow til i got home and parked it..next morning started the car push the button and the car raised up again...now im getting the sound every 25min...did anyone had this problem b4..could used the help to pin point the prob....thanks