Strange warm-up behaviour (Airlock ?)

[FFMan]

Went out in the Griff 500 yesterday which I hadn't done for a couple of months.

Whilst it was warming up, the temp gauge stayed on the bottom longer than I expected, then when I looked a moment later it was up near the red, and then it after a minute it settled to normal and was ok for the run. when I started it again to go home, it did pretty much the same.

we've had some very cold weather (-5) since it was last used, but its always got a good concentration of anti-freeze in it, but I wonder if this might be related ?

any comments appreciated.

[FFMan]

ok thanks - this could be the issue, as on the second occasion I fiddled with the heating controls and I got the impression this helped.

is it therefore perhaps better always better to ensure I start it with the heater valve open ?