Just to add that I am not aware that the ALDE system would require a service so maybe it is not necessary however a good idea to change the fluid from the 2 year to the 5 year.
This link takes you to the ALDE system and you may be able to expand your knowledge if you download the manual for the 3020 system. See
https://www.alde.co.uk/manuals-and-documents/ Hope it helps.
Past experience regarding noise is pump on 5 instead fo 2 and air in the system which is why bleeding is probably the firts step. We had this issue on our 2011 Lunar Delta.
All gas appliances over time may need a service. The manufacturer will normally suggest an appropriate schedule, to ensure their combustion tract and gas supply and gas air mixing systems are clean and working correctly, and especially those that are only used intermittently or stand inactive for weeks on end. Because of the conditions that most caravans are kept in, many appliances will deteriorate whilst being unused almost as quickly as wearing out from use.
Changing the fluid is a service activity!
Thank you for pointing out the documentation. However since I have retired from this area of work I have no intention cluttering up my PC with this documentation, especially as the OP has not specified a particular model which might well be different to the one you have suggested.
Like Damian I am not sure the OP's pump question relates to the heating system. Based on the title of the thread, it seems more likely he is referring to the cold water supply pump.
It would be more helpful if the OP could enlighten us please.