My experiences with a power steering box summarised.
May 1, 2023 14:20:32 GMT
Mike’S-a-loon likes this
Post by djm16 on May 1, 2023 14:20:32 GMT
1) I asked a question a few months ago about where the pressure was coming from to repeatedly force out the external dust seal (not present on earlier models, so here is my answer.
The top seal only comes under a modest pressure which is the low pressure return flow to the reservoir. This pressure should not be significantly affected by moving the steering wheel. Any pressure that exists there comes from the flow of oil being forced up the return pipe and through the filter.
That pressure will rise if the filter is a) old b) corroded c) plugged with crud from worn components in the steering box. Mine was all of the above, and since replacing the filter all has been well (it was of course not the only work I did on the box). So I am recommending replacing the filter as a matter of course if you do any work on the box.
2) leaking seals were entirely due to the ingress of metal flakes carried through the filter and wedging under the seal lips causing localised wear of both the lip and the shaft.
3) replacing seals. All four seals can be replaced with "universal rod seals". A rod seal is what keep hydraulic fluid in on a hydraulic ram when it is operating. It is "universal" because it has a sealing lips on both the internal and external diameters. I had planned to give universal part numbers for the four I used, but I have learned that many boxes are different from new, and even more will have been modified since. So you really have to measure your own. High pressure seals typically come with a spacer ring to keep the sealing lips apart and pressing firmly on rod and external mating surface. Good luck getting the seals in with the spacer ring in-situ. I discarded all four. To get a tip seal to fit, I had someone machine up a seal carrier to reduce the external diameter to something that would fit.
4) dust seal. My box has an external dust seal that sits above and outside the top seal. Just an ordinary bearing seal is fine here, but I did add a short length of pipe lagging to keep dust away from even the dust seal.
5) I had my box out recently three times, which is 2 times too many. The second time was because I didn't replace the filter, and metallic crud came through the filter, entered the box and cause the failure of top and bottom seals. The third time was because the box started locking first in one direction then the other then both. The cause was crud getting under the spool valves and holding them open, and this was despite carefully clean crud from the casing and replacing the filter. With the aid of a friend, we dismantled the spool too this time, and found an o-ring at its heart which had been misfitted by someone else years ago and subsequently crushed. It was likely this o-ring that disintegrated wedging the spool valves open.
6) my steering is now power assisted and does not leak, it does however feel very slightly stiff when cold, which I attribute to the rod seals gripping the steering column slightly until oil has had a chance to re-enter the seal surface.
The top seal only comes under a modest pressure which is the low pressure return flow to the reservoir. This pressure should not be significantly affected by moving the steering wheel. Any pressure that exists there comes from the flow of oil being forced up the return pipe and through the filter.
That pressure will rise if the filter is a) old b) corroded c) plugged with crud from worn components in the steering box. Mine was all of the above, and since replacing the filter all has been well (it was of course not the only work I did on the box). So I am recommending replacing the filter as a matter of course if you do any work on the box.
2) leaking seals were entirely due to the ingress of metal flakes carried through the filter and wedging under the seal lips causing localised wear of both the lip and the shaft.
3) replacing seals. All four seals can be replaced with "universal rod seals". A rod seal is what keep hydraulic fluid in on a hydraulic ram when it is operating. It is "universal" because it has a sealing lips on both the internal and external diameters. I had planned to give universal part numbers for the four I used, but I have learned that many boxes are different from new, and even more will have been modified since. So you really have to measure your own. High pressure seals typically come with a spacer ring to keep the sealing lips apart and pressing firmly on rod and external mating surface. Good luck getting the seals in with the spacer ring in-situ. I discarded all four. To get a tip seal to fit, I had someone machine up a seal carrier to reduce the external diameter to something that would fit.
4) dust seal. My box has an external dust seal that sits above and outside the top seal. Just an ordinary bearing seal is fine here, but I did add a short length of pipe lagging to keep dust away from even the dust seal.
5) I had my box out recently three times, which is 2 times too many. The second time was because I didn't replace the filter, and metallic crud came through the filter, entered the box and cause the failure of top and bottom seals. The third time was because the box started locking first in one direction then the other then both. The cause was crud getting under the spool valves and holding them open, and this was despite carefully clean crud from the casing and replacing the filter. With the aid of a friend, we dismantled the spool too this time, and found an o-ring at its heart which had been misfitted by someone else years ago and subsequently crushed. It was likely this o-ring that disintegrated wedging the spool valves open.
6) my steering is now power assisted and does not leak, it does however feel very slightly stiff when cold, which I attribute to the rod seals gripping the steering column slightly until oil has had a chance to re-enter the seal surface.
