Viessmann Vitodens 100-W dripping

[Our Gee]

Please can anyone help with the following problems with my Viessmann Vitodens 100-W System Boiler which is 10 years old.
First off I have had a water leak (about half a cup full a day) which is dripping from underneath the lower boiler casing plate via a 1"diameter unused hole (between the Domestic Water return and the Central Heating returns. I can't see where this leaking is coming from and would appreciate it if anyone can help.
Also when the Boiler is operating in Central Heating mode I have noticed that the Domestic Hot water flow outlet tends to be quite warm.
Any help and advice much appreciated.
Thanks

 

[ianmcd]

you will have to post a pic of the insides of the boiler, we dont have chrystal balls

 

[Our Gee]

Neither do I, hence my accurate description of the problem. Taking a picture would be of no value as the source of the leak cannot be seen from any attainable angle. I am hoping that someone whom has had a similar experience may be able to help, but thanks for your input.

 

[ianmcd]

But what is not visiable to you might be to us