Any time that the power steering system is repaired/replaced or is groaning/moaning or acting "strangely" this is the first thing to try in the way of fixing your problem. Anytime a P/S rack is replaced, a hose is replaced, etc.

1. Ignition Switch OFF
2. Raise Front Wheels Off the Ground.
3. Turn Steering Wheel Fully to the Left.
4. Fill Fluid Reservoir to "FULL COLD" mark and leave the cap off.
5. With assistant checking fluid level and condition, turn steering wheel lock-to-lock at least 20 times. Engine remains OFF. Trapped air may cause fluid to overflow. Thoroughly clean any spilled fluid to allow for leak check later. Keeping fluid level at "FULL COLD".
6. While turning steering wheel, check fluid constantly. For any signs of bubbles, check ALL connections (supply/return hoses, banjo fittings, etc.). If need be, after connections have been checked and remedied, Repeat Step #5.
7. Start Engine. With engine idling, maintain fluid level. Reinstall cap.
8. Return steering wheel to center (tires centered on their line of travel). Lower front wheels to the ground.
9. Keep engine running for at least two minutes.
10. Turn steering wheel lock-to-lock in both directions, slowly.

Verify:
Smooth power assist
Noiseless operation
Proper fluid level
No system leaks
Proper fluid condition, no bubbles, no foam, no discoloration

If any of the above problems exist, check all connections, make sure the correct fluid is being used (no transmission fluid, please). Then make corrections and start at step #1, again. Remember, NO BUBBLES. Entrapped air is the leading problem.

Don't Worry, Be Happy!

Long Rider's method above is good for a normal bleed. But if you screwed up like I did once, and turned the engine on before any bleeding, read on..

Air bubbles will make the pump shudder. Here's a LINK to a power steering bleeding method (VIDEO) that helped me, after I made a major blunder when replacing the pump-to-rack pressure hose on my 940 Koyo system. It inspired me to improvise with my hand-pumped MityVac, as explained below.

I had impulsively started turning the wheel back and forth with engine running, and got LOT of shuddering vibration at random spots in the range of L-R motion. At one point it got really violent before I could kill the ignition. Belatedly, I then went to the engine-off procedure, but apparently had whipped a lot of air (from empty new hose) into the fluid.



After several short engine-off bleeding sessions, and some short starter bumps to turn pump, the shudders finally became fewer and less severe. Then (after some googling) I rigged a nipple-fitted Master Cylinder cap to the PS rez and connected the MityVac. I had to caulk around the cap and nipple base to get a seal, then did more L-R hand-cycling. [Google turned up many versions of this vacuum technique.]

My rig held 12Hg vacuum overnight overnight so I cycled it slowly about 15 times, watching the gauge. I saw it dip about 2Hg a couple of times (at the right turn limit, with a bubbling noise as I recall), then rise back up to 12Hg. I increased the vac to 20Hg and worked with that by hand for many more slow L-R cycles. The need to pump up the vacuum several times showed that air was being drawn out, so I finally released the vacuum to cycle L-R with the engine running (and fingers crossed).



I still got some shuddering on this "Final Test", but with patience running thin, I decided to let the front end down to see if weight on the ground would have a snubbing effect. It did, with just a hint of vibration at first. There were a couple of slight noises turns on the first road run, but it's been fine ever since.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

When I replaced the steering gear in my 69 164 I turned it lock to lock twice in each direction
with the engine running. It was fine after that. Are rack & pinion systems that much different?
--
George Downs Bartlesville, Oklahoma

"Are rack & pinion systems that much different?"

I think so George, at least comparing the relative volume of rack cylinders to the older style gear box. More space for air to play havoc. But mine was an extreme case of stupidity. Usually it's been like Long Rider describes.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.