Confused by power steering/hydro boost system

[Tinker]

I just replaced my steering box with a Plews-Edelmann. I wanted to go ahead and flush while I have the hoses off, thinking I'd get out the old fluid before connecting the box, so I don't flood it with any debris. I filled the reservoir and started the truck with gearbox supply and return hoses stuck in a jug. Nothing came out. I had already drained what I could out of the system so thought I would give it some time and I ran the truck for a minute or so and pumped the brakes. Still no flow from the gearbox hoses.

I see a supply line from the ps pump to the hydroboost, a line from hydroboost to the steering gearbox, also an overflow line from the hydroboost back to the ps pump, a line from the gearbox to the cooler, and a line from the cooler back to the PS pump. My question is why am I not getting fluid from the steering gearbox supply line? I would think there should be high volume/high pressure coming out there. PS pump has plenty of fluid.

I've read over btfarm's flushing guide and will use that once I reconnect hoses, so this is less of a "how to" question and more of a systems question to better understand why I'm not seeing what I'd expect.

Thanks for your help.

 

[NVW]

Just a WAG, try turning the steering wheel.

 

[ak diesel driver]

I'd like to hear about a longer term review of this box

 

[Tinker]

Just a WAG, try turning the steering wheel.

I haven't reconnected the lines to the steering box. I was hoping to flush first and then reconnect, to keep any crud out of the new box. It's entirely possible the pump has failed, but it was working right up until I took the old box off, so probability seems low.

 

[Tinker]

I'd like to hear about a longer term review of this box

For sure. I'll let you all know how it goes. It's a different ratio than my stock Saginaw so I'll have to pull the steering wheel and re-center. That's the only thing I have to report right now.

 

[Tinker]

For sure. I'll let you all know how it goes. It's a different ratio than my stock Saginaw so I'll have to pull the steering wheel and re-center. That's the only thing I have to report right now.

Well, let me retract that statement on the ratio until I finish connecting everything. Quite possible I made an error in assuming it came pre-centered.

 

[ak diesel driver]

I flushed mine before I took the old box off.

 

[THEFERMANATOR]

Your pump is air locked. You have to fill the pump reservoir all the way up, leave the pressure line from the pump to the hydroboost off in a jug, and start the truck and give the throttle a quick blip if it doesnt pump right away, then shut the truck right off and then connect the pressure line. Letting it run without pumping fluid will DESTROY the pump as it is running dry.

 

[Tinker]

Your pump is air locked. You have to fill the pump reservoir all the way up, leave the pressure line from the pump to the hydroboost off in a jug, and start the truck and give the throttle a quick blip if it doesnt pump right away, then shut the truck right off and then connect the pressure line. Letting it run without pumping fluid will DESTROY the pump as it is running dry.

Thanks, I think you're right on vapor-lock between pump and hydro boost. Reservoir was full so I don't think any harm was done. I finally got it well flushed after reconnecting all lines and lifting the front to work the box through full travel. It took longer than anticipated, and a lot of steering/braking cylces but otherwise about what @btfarm said, roughly 3/4 of a gallon to completely flush.

 

[Tinker]

Well, let me retract that statement on the ratio until I finish connecting everything. Quite possible I made an error in assuming it came pre-centered.

The box did come pre-centered and I do have to re-center the wheel. Hopefully, I'll finish that this weekend.