My 1990 740 non turbo had a problem, when I drove it after a cold morning, it wouldn't heat up, so I took it home and found that the resivoir had ice in it. I put it in the garage and it heated up fine the next day and my girlfriend drove it to work. It was sub-zero that day and she parked outside and on the way home, it overheated. I drained the entire system, pressure tested it and it drives fine now but I noticed that it is losing coolant at about 1/2 pint per day, 60 miles or so. I noticed a leak from my tailpipe but only once, I changed the oil and it looks normal but it is a little loose, it drips off the dipstick when I check it and it never has done this in the past. Any solutions?? Thanks.