Geeetech

I've had my A10 for around 6 months with no issues. I went to print the other day and it didn't seem to be extruding right, my build was really brittle. I've cleaned the nozzle, no blockages in the teflon tube, I've bought new PLA & installed a new extruder but it still seems to be clogging. If I heat the tip and manually extrude it seems ok. If I heat then tip and then extrude by 10mm at a time it seems to be ok however when I try to print I am sure the filament thins and just wont print at all. The bed is level. There is just nothing coming from the nozzle. Can anyone help? I've seen one post which seems to suggest the teflon tube should push all the way through the heater - to check there is good contact but mine doesn't do that - i think there is a metal lip inside. The tip seems to heat up ok to 220 degrees. Im new to 3D printing as well so could really do with some help. Thanks