Sound.the issue is the temp if the heaters are on and driving it hardly goes up or if reved hard it drops rapidly changed thermostat and removed saab valve and replaced temp sensors heater do get hot eventuly poss dodgy thermostat.
Are the rad fans coming on and staying on all the time? It's quite rare for a thermostat to fail in the open positions in my experience unless the spring has broken. Can you plug it into a diagnostic reader with live data on it? Presuming it's a K-series it has 2 different coolant temp sensors on it one sends info to the ECU and will turn on the fans and the other is for the gauge on the dash. That might be acting up abit
Decided to take thermo back out and would u belive it it was jammed open so replaced that will see what happens when i go for a drive in a min thank you all will report back