"Andy Hall" wrote in message
...
On 12 Mar 2006 13:05:19 -0800, "Alister21"
wrote:

Suspects for early failure of the inhibitor and sludging would be
pumping over or sucking down of air in the feed/expansion tank. Have
you checked this carefully? Pumping over is obvious. Sucking down
will usually cause a sound of air bubbles being pumped around and it
will collect in the radiatrors.


Generally there can be 3 problems

1 Pump-over during normal running - disaster!

2 Pump-over when pump starts.

3 Pump-over when the pump stops.

I'd have said "suck down" is less likely because of the head of water which
has to be overcome for it to happen.

Any of the 3 will aerate the water with obvious consequences.