Radiator flush can't find the petcock location

locate the radiator drain plug (normally bottom right or left of the radiator) unscrew and drain coolant (beware of hot coolant) once unscrewed fully, gently pull and turn the drain screw/petcock until removed.

the refit and refill coolant. its also a good time to flush and change coolant,

Well the only petcock that comes to mind is the radiator drain petcock. It would be located in the bottom of the radiator plastic tank, at either the right or left end on the engine side. Many times the tabs that you use to turn it with are broken off, making it harder to see where it is. If you are going to do a coolant flush, just disconnect the lower radiator hose to drain the coolant; it is faster!
If this is what you are doing there is a vent screw in the top of the thermostat housing to let out air when filling the system. VERY IMPORTANT TO DO. I hope that this answers your question.

no there is a drain , its just towards the center from the bottom outlet hose , it doesn't look too much llike a drain , as its black and is down inside a well (this guides the coolant out) the well is about 3/4 inch deep and the drain plug turns via a tiny wing nut

You don't. You never open the petcock on radiators with plastic tanks because the petcock always breaks. If it doesn't break, it'll leak when you close it. No pro ever uses the petcock. You loosen the lower radiator hose clamp and yank the lower radiator hose. You'll take a bath, but it'll all be drained in about 1.5 mins. Then reconnect. You'll actually drain far more coolant that way too.

1. When setting the temperature to MAX, blower level to FULL and outside air Vent CLOSED, no hot air comes out after 2-5 minutes?
If YES, when did you last flushed your radiator and is it full?
2. if more than 5 years ago, flush radiator system, instructions are usually in Owners manual. Use a bottle of Radiator cleaner, run egine hot for about 10-15 minutes, carefully open petcock in bottom of radiator to flush out radiator, WARNING, careful as flushed coolant would be boiling hot. As sson petcock is open and water start to flow out, carefully open radiator cap to enhance flushing flow. Use garden hose to fill radiator while flushing until water coming out from petcock is cold and clear.
Once clear, start engine, turn heter full and blower full blast and keep hose in radiator flowing full, leave petcock open until clear water flows out again. Once clear waters comes out, turn off engine,turn off garden hose and let water drain empty radiator. Once it stops flowing out, close petcock snug and put radiator cap on, pull off radiator coolant catch bottle, clean bottle for any debris and dirt. Drain any water, leave bottle empty and put it back onto its place.
3. Fill radiator with 1 gallon (4L) of concentrated coolant, top up radiator until full, fill catch bottle with concentrated coolant, start engine and keep it overflowing until no bubbles comes out and the radiator is fully hot. Once it is flowing good, close and connect everything. Drive with it and keep catch bottle filled as necessarry.
Good luck. Give as vote and good comment if this advise solve youor problem. Thank you.

Just take the bottom hose loose and flush away.

The petcock is the bottom drain in the radiator.Turn it clock wise to tight..Its on the bottom drivers side of the radiator.Hope this was helpful.Have a great day..

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Disconnect your lower radiator hose...or open the petcock located on the lower corner of your radiator. Be sure to have your cap off.

Bottom corner of the radiator...called a "petcock".

the petcock is located on the drivers side of the radiator, at the bottom. it is plastic and just behind the front stone guard.