94 850 turbo coolant nightmare

I have a 94 850 turbo issue. about 4 months ago a "friend" decided to help me out and way overfilled my overfill chamber with water. Soon after this maybe 30 minutes my car overheated and the cap cracked and blew off due to pressure build up. the car has been slowly leaking coolant for a few months after replacing the cap. NOW within the last 2 weeks my 850 has been overheating after reaching 60 MPH. When I open the expansion tank the coolant is boiling and i lose most of the coolant in the tank.


We have checked all hoses for cracks, leaks, loose clamps, and such. new therm, added radiator sealant after finding a small leak, this cleared that issue but still overheating. ANOTHER expansion chamber cap, and $300 in coolant LOST!!!!!!


i do not have a loss of power, my fans are working properly, "idiot" light for the overfill is constantly fluctuating letting me know its low. I am clueless to this issue and its creating a huge problem. I now cant drive 5 minutes at low speed without it overheating.

Any suggestions? all of my coolant is being lost out of the expansion/overfill tank. it overheats and builds pressure.

please help.