Need help with power steerng issue

[43tutor]

Early this year I finished a complete restoration of my 72 Satellite Sebring. I've been chasing a power steering issue but can't seem to figure it out. When I first start-up the car the PS works great. No issues. As I drive the car (approximately 3 to 4 miles) the steering is fine at highway speed but as slow down the steering takes maximum effort. So I thought it might be RPM related. I tested this by putting the car into neutral (while at slower speeds) and increasing the RPM's but it doesn't seem to help.

Here is the history;

1. Completely rebuilt both the pump and steering box to factory service manual specs (new seals, bearings, bushings, etc.), Re-lapped all matting surfaces in the pump and checked clearances per service manual. I've taken every component apart and thoroughly cleaned all items before re-assemble. I'm confident the pump and steering box is re-assembled correctly. I documented the disassemble with photos and notes for re-assembly.
2. Adjusted the valve on the steering box so the car is not self-steering (completed this task with the front wheels off the ground)
3. Adjusted the cross shaft in the steering box to factory specs. Removed the cross link from the steering box arm and adjusted the box until the backlash was just removed and then tightened the adjusting screw 3/8 to 1/2 turn, torqued nut to 28 ft lbs.
4. Checked the movement of the front wheels while off the ground without the steering box attached, no binding
5. Checked the movement of the steering with the wheels off the ground, engine off, no binding or noise turning the steering wheel
6. PS fluid full
7. pump belt tight
8. PS lines from pumped not crossed they will only assembly one way
9. I have not checked the pump pressure with gages (I do not have a set of gages)

My guess at this point has something to do when the car starts to heat up after a few miles of driving since everything works fine when cold or the issue is in the valve on top the steering box.

Scratching my head looking for an answer.

 

[Coronet 14]

In my 72 manual it says the hoses must have 2 inches of distance from exhaust manifold.

 

[miller]

3. Adjusted the cross shaft in the steering box to factory specs. Removed the cross link from the steering box arm and adjusted the box until the backlash was just removed and then tightened the adjusting screw 3/8 to 1/2 turn, torqued nut to 28 ft lbs.

You tightened the backlash adjusting screw? If no backlash, same thing as clearance, but on gears...puts those gears in a bind.
Don't have my manual in front of me, so just suggesting doing a re-check on that. Heck, wouldn't be the first time I was wrong!!!

 

[43tutor]

Backlash adjusted screw correct set per factory service manual. I've double checked all my adjustments.

Could the steering box be leaking past the seal and applying pressure to both the right and left turn power assist side of the box at the same time? Once PS fluid is heated the viscosity would change and be thinner. Maybe leak by on the seals???

 

[bandit]

is fluid in pump foaming up after driving around for a bit? cavitation?

 

[747mopar]

I'd say it's the pump! Mine did the same (poor performance at low rpm's), when a pump get's worn it will produce enough pressure at higher rpm's but not at lower rpm's where there isn't enough volume to compensate for the leak by in the pump do to excessive clearances. New pump and life is peachy again.

 

[43tutor]

No foaming of PS fluid after heat up.

New pump - makes sense now that I think about it. As the fluid heats up the viscosity gets thinner and it could be leaking by the pump veins. The veins where near the upper limit on clearances.

I'll report back after the changing the pump. Thanks for the help.

 

[43tutor]

I changed the PS pump to a remanufactured today and all is well. I drove the car about 30 minutes and no issues with PS.