Marcel,
Some time ago in this '1936 Jowett in Germany restore' discussion, there was a photograph of an engine showing the filler cap and the oil level tube.
Look at the post by Peter Holden on Wednesday July 18 2012.
When you have emptied the oil from the sump, take off the little cap from tube 'B' in the drawing. The end of the wire should just be seen inside at the top of the tube.
Inside the engine the other end of the wire is firmly attached to a block of cork in the sump.
As you add oil through the filler hole (at 'A'), the cork will float on the surface of the oil and so the wire will start to rise out of the top of tube 'B'.
When the wire showing is about 1.5 cm long, this will be the
minimum amount.
When you add more oil the cork float rises and the wire showing will become longer.
If you look at the second drawing you will see that the wire passes through a special fixing to keep it straight. This also limits how high the wire can rise because the float will stop rising when it touches the fixing. This will be the
maximum amount.
You will see from the drawing that if you add even more oil, the float will not be able to rise further, so the sump will have too much oil in it.
Tony.
