I landed a plane over the weekend with only one gear due to an air leak. The first diagnosis is to pump things up and listen. If its a small leak its a little hard to hear. So I made a little tool. It is an old silicone ear piece from some device. Im not sure from what but a I had a bag of multiple sizes, a length of air hose, and a tube from a WD 40 can for a probe. I cut a bevel on the end of the probe for a little more surface area. I pushed one inside the other and tried it out . It worked great. the culprit was the filler valve that didn't check.
