thanks again Al, I have found a set of valves at a local delaer despite them being obsolete so will get these wednesday , try and flush the matrix out, but I have to agree with you I think that it is the matrix, but I'll get them in in case for future problems. the matrix loks a slow and careful job, but the fan motor is squealing so maybe a chance to sort them both out, I'll report back on these pages when I have replaced the valves and flushed it through.
best rgds,