More progress on 258. The front doors were not opening properly so the fault was traced to the operating valve in the destination box which was leaking air. We had to modify a Dennis dart valve of which we had a good one in stock by altering the pipework to fit. This done we then found that one of the door ram seals was also leaking air again from stock was renewed. We checked and adjusted the air pressure and the doors are working correctly now. Also the 2 x engine oil filters were renewed along with the fuel filter and the water filter.