You guys, hijacking my thread!!!!
I knew someone would notice!
Just one question in terms of reliability of pumps. How reliable are they? Can they go on without breaking for a year or two or is it more of a hit and miss?
I don't think I've ever had a pump fail in under that timeframe, although I've heard/seen instances where they haven't met the usually quoted 5 year lifespan.
Since you're going with a D5 I'll concentrate on that. To get the most out of the pump life it's a good idea to disassemble the pump once a year or so to clean it out. Depending upon how thoroughly you pre-flushed the system, how often you replace the coolant, if you use dyes, and what kind of biocide you use it's quite common to get a film of gunk between the impeller and the impeller chamber which will eventually take a toll on the pumps performance.
Basically, remove the impeller and wipe out the chamber with a very soft lint free cloth and a little isopropyl alcohol, then rinse thoroughly with distilled water.
The impeller is held in place by a reasonably strong magnetic field. Be very careful when removing and replacing the impeller to the impeller chamber- damaging the ceramic "ball" in the chamber is very bad news- second only to running the pump dry.
It's also a very good idea to replace the silicon O-ring at this time also, since the original one would be compressed and may not offer the best sealing when you reassemble the pump.
You can buy the O-rings individually, or in a bulk pack.
Most D4/D5 pumps seem to last many years. You might get the occasional pump that is DOA (usually from bad handling by the postal service), but generally, the pumps are solid and usually go the distance. A decent regime of changing coolant will help, and if you're using straight distilled water and silver as a biocide it will be better still.