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Discussion Starter #1
Hi Everyone,

Recently I noticed a leak on the PAS pipe from the pump to the rack. I am pretty sure it was the high pressure supply line which at the rack end goes into a loop made from aluminium before connecting to the rack. About half way along the pipe there was what looked like a connector , maybe a reducer or coupling although I could see no reason why it would be there?

Anyway I took it to a local high pressure hose specialist who fitted a new section of hose minus the coupler providing a single length hose from the connector at the pump to the fitting where the loop occurs before going into the rack. He had to use a larger internal diameter hose, something to do with his fittings. to fit the crimp connector at the pump end he had to heat and straighten the pipe then re-bend once the new connector had been crimped. Was harder to fit back ensuring all crush washer were in place, due to the less flexible hose.

Anyway after fitting bled carefully. Started the engine and now the pump makes a noise but only when the wheel isn't being turned. Turn the wheel and its quite as normal. I kept bleeding the system and air was constantly coming out but no leak. So did a complete flush replacing the fluid with the same red Dextron 2 pump still whines at idle.

Any ideas, not sure what the coupler / restrictor was on the original hose or if going to a larger hose bore might be causing it?

Thanks in advance

Nick
 

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That behaviour sounds like air is trapped in the pump. Perhaps try loosening the pump unions and running it, to expel any air. Needs rag to catch fluid.

Another possibility is that air is being drawn in via the connection to the reservoir.
 

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Discussion Starter #3
Thanks that’s really useful. I just want to check I’m understanding you correctly. You think air could be trapped in the pump so undoing either high pressure hose supply or return to the pump (I’d probably try the supply having removed it when I removed the hose) a little to try and vent air from the pump.

Not sure how the system could be drawing air from the reservoir as I only disconnected the rerun when the problem arose after changing the hose. Flushed the whole system through with new fluid.

Would not the full fluid swap vent any air in the pump?

Thanks

Nick
 

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Discussion Starter #4
Could anyone tell me the torque settings for the high pressure hose at the pump and the rack. I have downloaded Elearn but it needs a third party app to read and I am always loathed to do that on a MAC.

Thanks

Nick
 

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If, after installation, and with the engine running, you turned the steering wheel lock to lock a few times, that should have purged air from the system. However noise while the steering is not being worked (and hence not developing pressure to the rack) suggests cavitation from a small amount of air in the pump. Operating the steering will compress the bubble and silence the noise. Just a theory... But if right, try loosening the pressure hose to the rack a little, at the pump, in the hope the air is expelled. Then tighten the union.

Air could be drawn in if the feed hose from the reservoir isn't sealing properly at the pump. If so it may suck in some air rather than just fluid. Just another theory...

The other thing is whether you used the right ATF. My car seems hypochondriac about that. It groaned a lot under load with the old, probably OE fluid. I changed as much as I could for some Comma ATF2 before realising there are half a dozen different grades of ATF2. It was much quieter, but not entirely, and I don't know whether I used the right or best stuff. It's something I did last autumn and left, to revisit this year...
 

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Discussion Starter #6
Problem solved. Replaced the pipe with a second hand one from a really nice guy who posted it first class. Drained the old fluid, when I say old it was a week so kept it. Installed new hose. Refilled and straight away no more pump noises. Much happier now. Others might want to be warned having the hose repaired by a specialist might not be good idea!

Nick
 

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Interesting... can you see anything about the repaired pipe that would explain it? Union design trapping an air bubble, perhaps?
 
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