I just bought a Mint 67,000 mile 1991 740 Turbo recently (now has 80,000 miles) - It has ran well till now. Here is details of my problem:

Last week it was pretty cold - Everytime I drove the car with the heat on, the windows fogged up. Even with the defrost on full blast, the windows stayed fogged up. The defrost kind of had a coolant smell to it, but I Didn't think much of it at the time.

Two days ago (still cold outside) I was driving and I noticed that this time the heater wasn't even working at all - just blowing out cold air. Kind of bugged me, so I looked down at the dash and noticed my Temp gage was all the way in the red (with the Check Engine light on). I was just pulling into my place, so I stopped the car and shut it off. I didn't see any leaking coolant or steam.

Today I checked my coolant level and noticed I was two quarts low on coolant - I filled it up and I decided to drive the car again. I Drove till it reached regular temp (Check engine light was still on). Then I turned on the heat on defrost full blast and noticed a loud boiling sound coming from behind the dash. Then my car fogged up like crazy. I shut the defrost off. When I turned it back on, I noticed a puff of steam coming out from the defroster vent - smelled of coolant. Now I'm here writing the message to see if anyone can guid me in the right direction. PLEASE HELP! Sorry for the loong post, and thanks in advance for any insight

JODY