The Achilles’ heel of hydraulic steering systemsMar 31, 2015
Any steering system is just that — a system. Each part has to work with all the others for the whole system to work. It can best be thought of as a chain of connections that transfers the helm energy to the rudder to turn the boat. Like any chain, all it takes is for one link to fail and the whole system fails. This is why it is so important to not only inspect the major parts, but all the minor ones as well. The further offshore you travel, or the further from normal help and supplies, the more important this will be.
Hydraulic steering systems should be checked for leaks throughout the system, paying particular attention to the seals on the ram and helm unit. Make sure any flexible hoses are in good shape with no dry rot or cracking. Check all fittings and connections on all the tubing for leaks as well. Most systems will use metal tubing as this does not flex, giving the system a spongy feel. Follow the tubing throughout its run, carefully checking for corrosion or damage. Pay particular attention to where tubing passes through bulkheads, as these are areas where chafe and corrosion often occur. If the system is pressurized and has a reservoir, check the fluid level and pressure levels. Spin the wheel hard over and count the turns and note any noise while doing this. If it is noisy or there are an excessive number of turns, there may be air in the system.
As boat systems guru Nigel Calder writes in his definitive Boatowner’s Mechanical and Electrical Manual, there are several steps in bleeding a hydraulic steering system, but the key is to remove the air:
“Oil leaks are the main cause of problems on hydraulic systems. Small leaks can be handled by regularly topping off the reservoir until repairs can be made. However, if any air gets into the system it will cause the steering to feel spongy or even fail altogether. To test for air, put the wheel hard over in both directions; if it bounces back when released, that’s a pretty good indication of trapped air.”
Follow the manufacturer’s recommendations for bleeding air from the system. It often involves filling the reservoirs, using tubing, closing any cylinder bypass lines, turning the wheel to bleed air from the cylinder bleed screw and repeating the process, as some air may migrate up through the system to the top reservoir.
Also, make sure to check out part one of our steering maintenance video series.