GM Issues with one of service trucks that has the vt275 Frod clf 2008. Relaced the heads as they were cracked. Starts up idles fine. Go to drive and put a load and the motor still gets hot goes to 230 fan kicks on will drop to 210 same thing repeats. This is what it did with the old heads on it. EGR? or something in the block? Oil is not milky either. Thank you for any ideas.