A Common Cause of Overheating on 4.6L Northstar V8s | Hollow Bolt Location & Coolant Purge Line

If your 4.6L Northstar V8 is overheating, don’t immediately jump to the conclusion that the “head gasket” is bad, these engines actually don’t have “head gasket” issues, they have head bolt failures that mimic head gasket failures. “Northstar Performance” out of Canada goes more into detail on this subject, which you can find on their YouTube channel or Facebook page. Essentially the head bolt threads are too fine, old coolant reacts to the iron and aluminum causing corrosion which causes the bolts to “pull” after an engine overheats. If you see temperatures beyond 230 degrees but especially 240 or higher, your odds of needing the engine rebuilt are high. In this quick video I show you the location of one of the more common areas which will cause overheating. If this line plugs up you’ll overheat. This “hollow bolt” is a bolt and a coolant passage. Mine was clogged before. This bolt also holds the motor mount in, you shouldn’t have any issues to service this. Just remove the intake/air filter assembly, and the rubber hose, then the hollow bolt is a 15mm I believe. Run a coat hanger through or compressed air once removed from the engine. Same for the metal line which runs from the coolant crossover to the coolant expansion tank, this line is the “coolant purge line” when it’s not clogged, this line helps recirculate coolant, and expel trapped air, unlike other vehicles which require you to specially bleed air.