I am the proud owner of a very nice 1990 Deville 4dr Sedan. It was garage kept and given to my wife and I by her grandfather. Two days ago we developed a coolant leak. Lord and behold that with the hood up, I was lucky to even see the ground for the size of engine... . I had to take it to a local garage to determine the source. Turns out it is a rusted hole in something called or close to "rear heater outlet pipe". It is located on the firewall-pulley side of the motor. We contacted the Cadillac dealership here locally which contacted it's computer, anyway it has been discontinued and no dealership possesses one in the good ole USA. I have 2 part numbers and they are #1646975 and #22727133. If anyone can offer any assistance please let me know. At this point I have a Cadillac that I can't drive because of a 3mm hole in a metal line.