Final note on this autohelm
pump. I purged the system with 2litres of new oil
ram) bled both sides of the steering
ram, closed those and spent ages going from hardover port to starboard, each time forcing helm
further to bypass the relief valve. When returning the helm from pressuring the relief valve, more air would come up to the reservoir. This continued for maybe 20 repetitions. I don't think there is any leak, it just took a while.
pump.....when reassembling the hydraulic pump I replaced the o-ring which sits in a diamond shaped groove between the pump housing and the gear
housing. (Easily seen in the photos). I did use a 3mm whereas the old one was 2mm. I didn't think it would matter as there are 4 cap screws holding these aluminium blocks together; apparently hard against each other. Apparently not!!
While it sounded ok, the gear-pump whirred away but the ram didn't move, so it wasn't pumping oil
. I pondered for a while, wondered if there was air trapped in the gears?? Instead of disconnecting the hydraulic lines and taking the pump home, again, the one thing I could do in place was remove the gear
housing and inspect the gears. There is a partial scoring of the pump housing, created by the gears running against it, so the clearance is obviously almost zero. The gears are recessed into the gear housing, and I guess the thickness of the gears should be 'slightly' less than the depth
of the recess? Anyway, I put the old, thinner, o-ring back in, reassembled and it worked perfectly. I thought the thicker o-ring would have been compressed so as to not hold the housings apart, and therefore not affect the gears' ability to pump oil but obviously not. It is 'possible' that the fastening were not tight enough previously with the thicker o-ring, and didn't fully compress it, but I don't think so. Unfortunately I didn't check that before replacing with the old thinner o-ring, but I am pretty careful tightening things in sequence and firmly.
I'm sure these hydraulic gear pumps are not intended to be serviced, and I haven't tried to get drawings from HyPro Marine
to check clearances etc. but I guess if there was a problem one could go as far as resurfacing one or other face of these housing to improve things.
Anyway, lesson is these things are simple and well worth attempting to service
if you do your own work elsewhere.
I spent $5 on epoxy
glue, many hours and saved NZ$1200 , love it! Thanks again for the helpful comments.
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