Power steering rack over pressure?

[alan_thomas]

Anyone know if there is a failure mode of the power steering rack or pump that causes over pressure in the system?
I have new Power steering hoses both High and low pressure (old hi pressure hose was split) and when the steering is at max right hand turn it sounds like a significant load on the engine and the fluid is forced out of the joint between the pump and the hi pressure hose.
I have taken the joint apart and checked the flared end of the hose is in good condition, no foreign material in the pump side of the fixing. I have then tightened it up as much as I can (probably over torqued) the hose is being clamped tight but still it fizzes and fluid seeps out but only at max turn.
Should there be something in the rack or pump that relieves the pressure when at max turn and steering wheel is held at this position?

- Alan

[marshman]

Anyone know if there is a failure mode of the power steering rack or pump that causes over pressure in the system?
I have new Power steering hoses both High and low pressure (old hi pressure hose was split) and when the steering is at max right hand turn it sounds like a significant load on the engine and the fluid is forced out of the joint between the pump and the hi pressure hose.
I have taken the joint apart and checked the flared end of the hose is in good condition, no foreign material in the pump side of the fixing. I have then tightened it up as much as I can (probably over torqued) the hose is being clamped tight but still it fizzes and fluid seeps out but only at max turn.
Should there be something in the rack or pump that relieves the pressure when at max turn and steering wheel is held at this position?

- Alan

There is a pressure relief valve shown as item 2 in the attached diagram, it is in the pump. In order for it to operate the pressure has to rise and it is there to protect the seals in the rack. In my opinion t is bad practice to hold power steering on full lock. On my old Landy 110 if you do this for more than 30 seconds or so the seals fail in the steering box due to the increased heat and pressure - a known problem on the older Landies, turn the wheel to full lock and then back off a touch. I always end up shouting at the MoT guy at the annual test as he sits there holding it full lock. On most cars with power steering you can hear the pump start to complain and the engine revs drop (on none ECU engines) as it has to work harder. The hi pressure joint should not leak, the seals should go first so the flare or something is not mating correctly. It is possible you have got some dirt in the system which has affected the relief valve. A pressure gauge would show if the valve is working.

Roger

[alan_thomas]

Thanks Roger that certainly sounds like the problem as on extreme lock it is enough to force the belt to slip with a screeching sound but cannot see any attachment to your post. I have been looking at the parts book and Rimmers site and cannot see any mention of any valve but browsing I found these pages. the first is an exploded diagram of the pump and the 2nd explains the stripdown.

http://www.triumphstag.net/start/tec...ages/57.05.jpg

http://www.triumphstag.net/start/tec...g/steering.htm

As I really do not want to have to rebuild the rack seals I may have a go at stripping as per this link, hopefully it is only debris blocking the valve. Just checked and my pump appears to be one where the pulley is pressed on rather than being retained by a nut :-(

- Alan

[marshman]

Not sure why you can't see the attachment, I can see it on my laptop and my tablet. It is the same as 57.04 in the second of your two links. I would try to determine if there is a problem before stripping the pump. My belt sometimes squeals if you hit full lock. Power steering hydraulics are usually pretty bomb proof (bar leaks from seals on the rack). As I said the joint shouldn't really leak even if the pressure is a bit excessive. It could be that the leak is preventing the pressure from rising high enough for the pressure relief valve to open.

The R.O.M. gives a running pressure of between 750 and 850 lbs / sq in.

You should be able to access the relief valve without removing the pulley as it is on the back face of the pump. Have you got the R.O.M? (repair operations manual)? If not you can download a copy here....

http://www.grampianstags.net/Stag%20Repair%20Operation%20Manual.pdf

Roger

[davidf]

Just checked and my pump appears to be one where the pulley is pressed on rather than being retained by a nut :-(

- Alan

I think that instruction '6 Remove pressure outlet complete with 'O'ring and withdraw relief valve/flow valve and spring.' is not dependant on the previous steps - perhaps someone else could confirm that.

[alan_thomas]

Will have a go pulling the relief valve today I have the ROM but completely missed those pages
With regard to not seeing the attachments its strange if I log out I can see them. When I log in I can't. Also the order of the posts is reversed when I log in the originating post is at the top and then the newest with the oldest at the bottom Logged out the originating post is at the top followed by the oldest with the newest at the bottom, What's going on??

- Alan