Hi Smithy

The JJ-1800 uses pressure differential between the rear of the compressor and the shaft tunnel to get air and fuel/oil flow through the bearings. The JJ-1400 is different and uses pressure differential between the combustion chamber and the shaft tunnel to take cooling air and lubrication to the bearings. There is a ring on the rear of the diffuser into which the lube line is fed (oulet is just in front of the front bearing) and air then feeds into the gap around this line and down the shaft tunnel. It is possible that the hole around the lube line is not large enough and that there is not enough air flowing down the shaft tunnel to push the oil all the way to the rear bearing. Another problem may be if the seal between the rear of the compressor and the diffuser is not good enough, then the air and lubrication could be getting sucked back into the rear of the compressor and is not going down the shaft tunnel. This would normally show up with evidence of fuel/oil on the diffuser.