Just bought my 97 540 coolant light popped on. thought maybe just an air bubble in the system topped it off about a week later yet again "low coolat" i checked the oil dipstick and cap to see if it had a nasty white build up on it (bad head gasket) looked good to go. NOthing is leaking on the ground. I thought maybe heater but it seems to be working fine no moist windshield. I have no idea where the coolant is going? Is there anything i can check? I know my way around a car but this is just crazy, my next step was to get a coolant presure tester and see if i can see anything that way, but that is money i currently do not have. Any help would be great. Even some commonly known places for it to leak would be helpful.