hi, what is the correct way to flush the radiator. as i've never done one a 5ltr before.

same as any other radiator mate, dump coolant, flush radiator if you like and refill
just remember to bleed the air out of the system.

Mate
On a au u need to make sure the heater tap is compressed on to allow water to flow thru the heater box. if not you will get hot spots that can damage the engine

gassa

how do i know if the heater tap is compressed, is it when i turn the heater on full temp & fan ??

Yeah once you've re-filled the system and are ready to start it up. Leave the radiator cap off, start the engine up, let it idle and have the heater going to bleed ALL the air out of the system. Let it get to operating temp (thermostat open) then re-fit the cap.
I always flush the heater system too when i do a coolant change. Basically just remove the tap from the two lower hoses and flush through one untill clean water comes out the other.
When i done my ute, i went all out and flushed the heater system with distilled water, didnt want no dodgey Perth tap water contaminating my cooling system at all.

Mate
1 final point make sure you add 40% concentrate coolant to the water 2 keep the temperature down

gassa

thanks for the replys guys, done it today car running a1 now