Sounds like you have found the issue.
Since my original post I've renewed the Diaphram pump and the Heat exchanger both from Ebay sources. Its worth keeping an eye at whats available as you can get new parts cheaply and keep them as spares. I wouldn't change the heat exchanger unless you see weeping between the joints. I changed mine for that reason.
Have fun
Tony
Since my original post I've renewed the Diaphram pump and the Heat exchanger both from Ebay sources. Its worth keeping an eye at whats available as you can get new parts cheaply and keep them as spares. I wouldn't change the heat exchanger unless you see weeping between the joints. I changed mine for that reason.
Have fun
Tony