Hi, I had a K series which was a devils own job to bleed the air out after radiator changes etc.
I now have a 150 Sigma which seems to have developed a mind of its own with regard to expansion tank level. I have fitted a bleed tee, jacked the car right up at the front (high enough?), checked the bleed tee, full to top and ok, took plug out of radiator, filled it, checked expansion tank somewhere sensible, put cap back on, lowered car, level at max, drove car, level now 20mm above max. when hot, same when cooled down. Conclusion, air still in there somewhere. Any ideas gratefully received.