Mechanics

PRESSURE IN POWER STEERING RETURN LINE

1998 Ford Windstar

Steering problem
1998 Ford Windstar 6 cyl Front Wheel Drive Automatic 150000 miles

Somehow, pressure is building in power steering return line between steering gear and pump reservoir & blowing the line apart in different places. I cannot find anything that could cause a blockage. Have blown thru line with air & seems ok.

What could cause pressure to build up here?
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Rex Jameson
February 25, 2009.




Pwr Steering return line is designed to be low pressure, so there's got to be something blocking the path. It may require some logical diagnostics, but work your way from the pump back to the rack/pinion trying to find the blockage. Remove hoses and connections one by one, starting nearest the resovoir. Blow into the hose towards the resovoir and see if there is free flow.

When you get to a connection which no longer allows air flow, you know the blockage is someplace between that connection and the one you tried previously.

You mentioned " blowing thru line with air and seems ok.&Quot; If you disconnected the hose at the pump resovoir and air passed thru, then the blockage is at the resovoir inlet nipple. Remove pump, detach resovoir, and inspect. Clean or replace as necessary.

Tiny
Schrimpieman
Feb 27, 2009.
Thanks, you confirmed my thinking. I've done as you suggest and can't find a blockage. I put a pressure gauge on the line. On startup (cold morning) pressure spikes to about 450 psi for about 30 seconds then drops to about 100. After idling for a minute or two, down to about 50. After warm up down to about 30 or 40.

Any thoughts on why the high spike? Can't be just the cold oil, cause it drops pretty quickly after the first spike.

Tiny
Rex Jameson
Mar 1, 2009.
By any chance you have the pressure lines reversed? Either on the pump itself (highly unlikely), or if there was some work done on the rack/pinion, if the lines are reversed on the rack?

But even on the rack/pinion, I think there are two sizes of spin-on connectors, so reversing them is impossible.

If the reversed-connector idea is not applicable, I'd recommend removing the pwr steering pump and paying special attention where the return line plugs into the resovoir. There's got to be a blockage there.

Tiny
Schrimpieman
Mar 4, 2009.
I have not had the lines completely off, so they are not reversed, but here is the latest.

If I run a piece of hose about 10 inches long from my pressure gauge to the bottom of the reservoir, gauge shows no pressure in return line, even when starting from a cold condition. So the inlet to the reservoir is ok.

Reconnecting from the gauge to the cooler tube and back to the reservoir results in high pressure again. So I figured tubes are plugged. Replaced them with new. Same result.

Replaced power steering fluid with ATF type F fluid. Pressure drops to about half. Cold morning, starts out at about 200 psi now and drops to about 80 until it warms up, then drops to 20-30.

Any thoughts?
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Tiny
Rex Jameson
Mar 14, 2009.
I ran into this scenarion one time: I'll try to explain it best I can.

The factory hose (in part) is composed of both metal and rubber. At the junction of one of my customer's hoses (where the metal crimp meets the flexible rubber), there was a rip to the inside of the hose. It was not distinguishable at all from the outside. So as the PS Fluid flowed, it pushed a ripped portion of the rubber hose and acted like a check valve. I was about to give up, but started to disassemble each junction one by one to search for the obstruction. I used a dremil cutoff tool, slid off each hose off it's metal counterpart, and. Whaddya know? One junction had that ripped hose on the inside acting as a check valve. The ripped portion of rubber would bend as fluid started to flow, causing the obstruction.

Try to do your best in process of elimination to determine where the obstruction is. Maybe you have a hose junction acting like a check valve.

Tiny
Schrimpieman
Mar 18, 2009.

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