l322 4.4 lpg cooling question

hi can anyone tell me if its normal for radiator top hose to be hot while hose at thermostat left side is cool water system is pressurised and car is running normal with temp gage in mddle engine management light is coming on intermittently but resets after a while but not all the time i had to fit new expasion tank 2 weeks ago and on first long run she airlocked any help would be appreciated