2003 FReelander v6, rad. issues

HI folks. JUst wondering if any of you have ever flushed your rad on the V6 model. THe coolant gauge needle fluctuates wildly, at times, and the overflow reservoir, will build up pressure, which, once released negates the needle variances. Is this normal? It seems if I burp the cooling system. occasionally, and top up the coolant, which is usually quite dirty, the problem goes away...? Any advice for this mechanically-challenged pastry chef, would be greatly appreciated! Thanks in advance...Anthony.

did you follow the correct procedure?

The V6 cooling system is very prone to airlocks, and it seems to be a bit of an art to clear them properly.
I had to get my local dealer to do it in the end, but they did a fantastic job!

When was the last time the coolant was fully replaced?