Recently purchased 1985 RX7 GSL SE with 13B engine.Car was in storage for 15 years registered non op had 119k miles. Cleaned fuel lines flushed fuel system cleaned injectors ,new fuel pump, new filter ,battery cables , battery, new master and slave clutch. brakes were good , Oil and filter change new wheels and tires. drove 17 miles to smog station PASSED perfectly. I was impressed drove car 200 miles no problems. drove 80 miles a few days later no problems. Drove car again days later 20 miles no problems, started car Monday morning let warm up 20 min before drivng to work idle at ~800 RPM. Pulled out of drive 1st, 2nd 3rd gear down shift for stop and car stalls out and will not start acted like no spark. Pushed car home. That eve after work I got in car and it started up , but idle was really rough had white smoke coming out of one exhaust I let car run 5min to see if it would clear up no luck. I felt radiator hose at inlet hose warm radiator was cold and coolant light came on and then went out. I removed radiator cap safely water was cold as ambient was around 50 degrees. I need a new thermostat obviously, But what the hell else did I screw up an APEX SEAL? NEED HELP.

 

Most likely the coolant seals.

 

Certainly sounds like a coolant seal failure which wouldn't be surprising if it had sat for 15 years.

let it sit over night pull the plugs in the morning and rotate the engine if you get coolant from the plug holes that's pretty much that.