Northstar Engines and System Technical Discussion Discussion, Northstar oil flow diagram - oil in a head bolt hole in Cadillac Engine Discussion; Does anyone know if we have a diagram of the oil flow within the Northstar engine on the site?. I ...
Thanks for the reply. I am in the process of the 125,000 mi head gasket replacement due to the center upper head bolt failure & when I removed that particular bolt it was soaked in oil. Only thing I can think of is an adjacent oil port to the head filled the bolt cavity with oil as the holding pressure of that portion of the head gasket weakened. What do you think?
Oil is supplied to the heads and drains back to the pan through dedicated delivery channels and 3 drains in each head and the block. If a head bolt or head bolt thread failed it's entirely possible that an adjacent oil supply or drain channel could weep oil into a bolt hole.......... but oil would not eat through a gasket and soak the bolt hole. The head was loose first. (and a LOT of oil drains from those valve and cam areas)
Thanks for the input Sub----Actually when I pulled the head off what filled the bolt cavity was oil from the cam spray. When the threads failed, and through a number of head heat cycles, the bolt lifted approx .030 away from the head surface allowing oil to flow & fill that bolt cavity.
You learn something every day
So do we; The point about the bolt itself actually being lifted from the head boss surface before you removed it goes a long way toward explaining the "gasket first or coolant first" argument............. and it would take nowhere near .030" looseness to cause a gasket leak.