another 4.6 overheating any suggestions

hi any suggestions my 4.6 has just started overheating, turn the heater on full blast at high and it levels back out to half way, checked the top hose and it was solid could not squeeze it so there is presure in the system may be a blockage somewhere? its had a new thermostat and pressure cap and a new rad is on the way and has a kenlowe electric fan, had a sniff test done a few months ago and it came back ok? the old girl can drive me nuts some times!

You say you had new thermostat fitted, it could be you have an air lock

oh dear been there done that , get another sniff test done mate .
also check the tube that vents from the top of the rad to the header tank , they block up and cause all sorts of problems , dont forget the nipples either that the tube goes on to as these also block up .
ive just replaced the engine in my 4.6 due to slipped liner fault i did a sniff test on it 12 mths ago and it was clear , i always drive my p38 with one eye on the temp gauge anyway but, on christmas eve as i pulled off the motorway totally without warning the temp gauge went straight into the red !!!!!!!, an sniff test the next day shown that there were combustion gases present in the cooling system .
i just hope you have more luck than i did mate .

rick.

what a relief had a snif test done today came back fine already had ordered a new rad as im converting it to lpg this weekend, gona pull the thermo out and give that a go over just in case thou thanks for the suggestions, can sleep a bit better tonight