How Mechanics Test For A Warped Engine Block!

How do mechanics know if a car engine is permanently warped?! ⚙️🔧
When an engine overheats, the massive temperature spike can cause the solid aluminum cylinder head to physically bend and warp! If you try to install a brand new head gasket onto a warped block, the engine will instantly leak compression and blow the seal all over again.
To test if the metal is perfectly flat before assembly, mechanics use a brilliant visual trick! They coat the mating surface in blue machinist layout fluid and rub a heavy, perfectly flat metal straight edge across it. As the precision tool slides, it scrapes the blue dye completely off the "high spots" of the metal, while the warped "low spots" stay stained blue! This instantly tells the mechanic exactly where the engine needs to be machined flat!