If air is gettin in, there is definitely fluid leaking out, trust me. Check the end caps on the cylinder. Run your fingers or a white rag right around the bottom. Look in the splashwell for any drips. If there is bulkhead fittings check'em. If there is copper tubing for your lines, check those too. What size boat? Lines might be joined or lengthened where you can't see it. Possibly rubbed through on exposed/rough surface. Possibilities are endless. Check them all. And as mentioned, the back of the helm.
