Coolant Changing

[VYMAD]

Hey, just wondering, has anyone noticed that when you change your coolant; you know, drain, flush, fill, bleed that for a week or two there is a slight "pinging" noise under acceleration, which soon goes away especially after a long drive? Have done a few now on vy's and a vt and found they have all made the same noise, maybe the belt slipping a bit due to coolant getting on it?

[VYMAD]

Any one????????????