Hello
I am about to have the engine replaced in my 03 g35 coupe due to a cracked head...
I was wondering if I would need to have any work or flushing done to the cooling system, since I had oil and coolant mixing into each other
thanks in advance

 

They should replace the coolant via flush anyways when the new motor is put in.

Note: These motors are a royal PITA to flush and get all the air out. Highly recommend they use a vacuum system to remove the air completely. Its 1000x easier and you know the air is out completely...i spent numerous hours trying to burp and bleed the system manually and until I used a vacuum type system it still had air in it...