1-Remove the 5 cheese head screws securing the steam valve cap
These screws are notoriously fragile and will break easily if stuck or overtorqued. I found them to be a non standard size, so I used plenty of W40 and an adjustable spanner. Tools: Small adjustable spanner
2-Steam valve cap partially removed
Notice that the two screws securing the warning plate are longer and also have thick washers.
3-Steam valve cap removed
The sealing gasket has to be scrapped.
4-Scrapping the sealing gasket
Takes time if you don't have a special product for doing so
5-Pulling out the steam valve
It just sits into its recess. If stuck, use a pair of pliers and do gently. Notice how it comes because it can easily remounted upside down.
6-Remove the Washer fitted beneath the steam valve and cleaning the surface where the new seal gasket
7-Remove the remaining hoses
The drain pipe is most certainly dry and soldered to its pipe. You'll have to cut it.
8-Obstruct the header tank pipes and fill it with a mixture of 10% citric acid - 90% water
Let it rest one hour or two then clean with mains water. This is done in order to decalcify the inside of the tank. But not mandatory.
9-If needed, repaint the tank using back high temperature gloss paint.
Prior to painting, clean the surface.It is a lot better if with a spray gun Tools: Spray gun
10-Fit a new inner sealing gasket in the steam valve recess
Spare Parts: Seal for steam valve (UR15870)
11-Fit the steam valve
On this picture, the valve is facing upside down. Also notice that the little hole on the side of the valve has to be facing *in front* of the little hole you can notice in the recess. This part is not known as failing often. A new valve would cost around 100 GBP. Spare Parts: Steam valve 15psi (UR16730)
12-Fit the steam valve cover gasket
Spare Parts: Steam valve cover gasket (RH12745)
13-Put the cover and screws back in place
Note the long screws and thick washers go for retaining the warning plate. Beware of making the text face the rear of the engine, or just the drain pipe that you see in the rear (just not like on this picture!)
14-Torque the cheesehead nuts moderately
Avoid using too long a wrench. If possible use antiseize coating on the threads.