Grant 90 boiler leaking...HELP!

[mrbriggs]

Why would I replace the boiler? What looks like corrosion round the area of the valve is just insulation, it actually looks really bad in the picture doesn't it!!!

The auto air vent I have got is very similar to the 7703/4 parts in that link. I seem to recall it has a button on the top which the existing one has not got. How do they work exactly?

Also, how do i fit it? Do I need to drain down the system? Do I need any sealant on the joint?

Thanks guys.

 

[oilman]

How do they work exactly?

Trade secret.

Also, how do i fit it? Do I need to drain down the system? Do I need any sealant on the joint?

Open pressure relief valve.
Wait till pressure is zero.
PTFE tape over threads on new valve.
Unscrew old, screw in new.
Check correct air pressure in expansion vessel.
Repressurise system.