I have a 95 850 turbo that recently has started overheating. It is blowing coolant out the lid of the reservoir when the car is turned off. I changed the thermostat about 2 months ago because the gauge was not consistent. By mistake I got the higher temperature replacement. The car has been fine the last couple months since the replacement even on longer trips. This started all of a sudden after about a 300 mile trip. The guage still reads the same as always. I'm stumped. I plan to get the lower temperature thermostat and replace but I'm not convinced it is the problem. Any ideas?