Piston with old seals removed:
Piston seal guide and shaft seal guide on bench with shaft & piston assembly. I did not think to take an image of the piston seal guide in use. It slides onto the shaft with the tapered end upward (i.e. away from the piston). You then apply plenty of Dow Corning 111 (Molykote) over the guide and slide the top piston seal down the guide. The guide enlarges the seal to the diameter of the piston, making easy work of fitting the seal without damaging the seal. To fit the bottom seal you slide it over the guide in the same manner as the first seal, but once you have the seal down towards the base of the guide you take the guide off the shaft and present the wide base of the guide against the base of the piston and slide the second seal on. Flange on the top seal point up, flange on bottom seal points down.
Shaft seal guide in place with plenty of Dow Corning 111 (Molykote) seal lubricant smeared on it. Without this guide it can be difficult to get the shoulder of the shaft through the shaft seal without damaging the shaft seal. With this guide and the Molykote lube there is no risk of damaging the shaft seal.
It isn’t especially visible in this image as it isn’t well lit inside the bore, but we spent some time cleaning the coffee residue from the bore with surgical alcohol to get the worse of it off, followed by metal polish to remove the staining left behind. Wash the group thoroughly with really hot water to remove all traces of the metal polish before reassembly, particularly from the water inlet and recirculatory holes in the wall of the bore. I expect the household cleaner Cif/Jif would be better suited to the taste than surgical alcohol I might well mean the you wouldn’t need to use the metal polish at all, but I didn’t have any Cif/Jif to hand that day.
The shaft with the guide still in place exits at the top of the group:
