I dunno - it takes time for the cooling system to warm up - if you saw a pressure rise on a cold engine it would maybe give a warning of impending HG doom.
I have had very subtle HG failures twice where garages could not diagnose it with their normal test gear,but the symptoms were unmistakeable and I got the HG's changed - symptoms then disappeared LOL - funny old thing eh
I also wonder what the actual running pressure is with the coolant at normal temps (circa 82 deg) - I doubt that the cooling system is running at the cap vent/relief pressure all the time - to be sure it will prob vent when you are stuck in traffic on a hot day and also if you come to grinding halt (roadworks etc) after a long fast run on an Mway then the heat soak will bring things nicely to the boil.
I have had very subtle HG failures twice where garages could not diagnose it with their normal test gear,but the symptoms were unmistakeable and I got the HG's changed - symptoms then disappeared LOL - funny old thing eh
I also wonder what the actual running pressure is with the coolant at normal temps (circa 82 deg) - I doubt that the cooling system is running at the cap vent/relief pressure all the time - to be sure it will prob vent when you are stuck in traffic on a hot day and also if you come to grinding halt (roadworks etc) after a long fast run on an Mway then the heat soak will bring things nicely to the boil.
