Basically from here you can see sludge deposit, cam wear, and from this you see piston top, then you see external components and coolant side pipes and bolts. Every single thing of cooling system and oil system and external components. And then you sketch a rough estimate by the help of your previous engine purchasing experience..
And then you are like its new engine or a less mileage engine. Now by this methodology it's never 100% sure that it's a good engine. You bring it, you fire it up. And then see oil pressure, engine noise and then connect obd2 adapter and see if the cooling system is working properly.
Like fan kicks at correct temperature, and turns off or goes up or stucks at 100. You can't still say it's a gasket issue if you stuck at 100 or beyond.
Now you use old results from which you made the decision to purchase it, you'll be like yar there's no rust anywhere how can this engine have any gasket issues, it has clean coolant lines. After this you see for leaks and then if you're experienced enough you'll be able to solve air leak issues in coolant lines and then in the end you'll get a silent and good engine ready. Like I've swapped this engine successfully... Anyone from Islamabad rawalpindi is welcomed to see it. Having this car with me for some work...
I've provided ac services and heater core flushing services along with m16 injectors...