I posted this in general too, but when the steering is straight, shouldn't the rack's valve be in bypass, i.e., no buildup of hydraulic pressure?

I have a leak at the high pressure side of my pump I can't fix, and it froths like crazy at the fitting when I rev with the wheels straight, I'm wondering if the pressure is too high because of a rack problem...

 

short answer-yes.


the pump is a positive displacement vane-type pump (protected by an internal spring actuated relief) that always produces fluid flow to the rack selector valve.
the selector valve returns pressurized fluid via the return hose to the pump at any time when the rack selector valve is not deflected by steering (wheel) input...when the car tires re-aim in response to the steering input, the rack selector valve returns to full pump return even if the rack is not centered....pump output is continuous at relatively low pressure and rises if the rack selector valve is deflected and flow to the return hose is re-directed to one of the two rack steering assist rams. ...note that the rack ''rams'' are served by only one pipe (ok, tube) and if the rack selector valve is held actuated to supply a ram when the tire cannot move, full potential pump pressure(up to the pump's internal relief spring blow-off limit ) will be deveoped in the entire circuit, from the pump to the selected ram (the rack selector valve ''dumps'' the non-selected ram back thru the pump return hose)

the pump pressure hose fittings rely on ''0-rings'' to seal, and excessive tightening of the back-up nut will not stop leakage due to a defective 0-ring...metal fatigue due to long-term exposure to service vibration may also produce minute cracks in the steel tube adjacent to the nut.
try a new 0-ring first (abt 40 cents at any auto parts store) before changing the hose assembly...pay close attention to prevention of dirt entering the system, one grain of sand could be the cause of your present problem

 

Thanks Andy, I've tried 5 O-rings now and although I can't see or feel any cracks in the tube at that fitting, there has to be one. I just found some bubbling from the fitting with slight air pressure in the line.

The new hose should be here tomorrow, I'm keeping my fingers crossed but it looks like my rack should be OK.