Our 1995 940T has about 90K miles and has a slow coolant leak. I filled the expansion tank to about halfway between the min and max line and after about a month the tank was just about empty. In the past it has gone 2 years at a time between coolant flushes without ever needing to be topped off.

I don't see any obvious leaks nor have there been any spots on the driveway. Given the age of the hoses I had ordered new heater hoses and heater control valve (currently these are original). While at it I was going to replace the radiator hoses and thermostat (were replaced once a few years ago). The expansion tank has been replaced in the last year as have the two small oil cooler hoses near the oil filter.

I am hoping that the replacement of these hoses may solve the leak problem, but what else could be going wrong? Should I do something else while the coolant is drained?