I emailed Bachmann and got the following reply:
Thank you for your recent e-mail
The instructions are unfortunately of the earlier type and have not been updated yet. On the left hand side of the model, the speedometer cable sits just in front of the cab. The crank screw can be removed to allow this part to be removed and the body released.
Assembly has been revised several times in China, on some models the bracket supporting the pipework will remain with the chassis as its removed, on others the bracket will remain with the body. In this case, the pipework may need to be cut unless it’s possible to ease the pipework off the bracket. This arrangement has not been repeated on the later models like the Fairburn tanks.
Regards
Jenni
I decided to have another go. I could not get the screw out holding the speedo so left it attached. I cut one of the pipes on the other side but instead of a clean cut it broke off around 4mm worth completely.
The pipework jumble under the cab door was gently moved over its support bracket, but the pipework behind this would not budge.
All this movement allowed me to lift the boiler just enough to prop it up using a pencil between the body and chassis whilst I fitted a decoder.
How on earth the pipework which was stretched to the limit did not snap I will never know, but the job is complete and the loco running.
I have just had a Model Rail USA tank delivered and the instructions with that are far superior to the 4MT tank.
Paul