Power steering with hydro boost

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Shiny

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I have a 1999 CCSB 2500 with a 7.4L. It has the hydro boost power steering/brakes. I got the truck from my brother who replaced the power steering pump on it as well as the lines to the gear box and hydro boost. I have checked the fluid level in the reservoir and it's good. I have no power steering at idle and if I rev the engine up to 3000 it will work but the pump is noisy. Break pedal seems good, it feels like it is working with assistance from the hydro boost.
My question is, why would there be no power steering? Also what fluid should I be using? Can I use hydraulic fluid like AW46? Or is this power steering pump junk?. Thanks in advance and sorry for the winded question, I'm just trying to explain in detail what I know about the truck. I hate being the person that throws parts at something until it is fixed only to find I have wasted a bunch of time and money to get to the end result.
 

someotherguy

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Most likely the new pump is junk. Either it was bad out of the box (happens more often these days than you'd think) or it was improperly bled after install and damaged that way. Some people put fluid in, crank it up, then start turning the wheel left/right and that is not the way to bleed it. The air pockets in there combined with loading the pump will hurt it.

GM has a pretty specific method for bleeding the pump, and it should be followed to the letter. It's close to what most people do, but with a few extra steps.

You must be registered for see images attach


For the fluid, generally I would say running ATF is just fine, but with hydroboost you want to run actual power steering fluid. It's less likely to foam up than ATF, in this application.

Richard
 

kkirwan71

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Most likely the new pump is junk. Either it was bad out of the box (happens more often these days than you'd think) or it was improperly bled after install and damaged that way. Some people put fluid in, crank it up, then start turning the wheel left/right and that is not the way to bleed it. The air pockets in there combined with loading the pump will hurt it.

GM has a pretty specific method for bleeding the pump, and it should be followed to the letter. It's close to what most people do, but with a few extra steps.

You must be registered for see images attach


For the fluid, generally I would say running ATF is just fine, but with hydroboost you want to run actual power steering fluid. It's less likely to foam up than ATF, in this application.

Richard
Saving that pic for future reference. Thank you

sent from my glade air freshner
 

Shiny

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Ok this would make sense to me. I just wasn't sure if I was missing something in the hydro boost area, like the spool valve. I thought it could be causing the fluid to not pass correctly to the power steering.
Thank you for the link and the reply. I will take the pump out and replace it if there is no other way to test it.
 

Shiny

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Update, I have got a new power steering pump.
I pulled the pulley off the old one and removed the three bolts holding the pump to the bracket but I cannot get the pump to drop low enough to come out of the bracket. There
Is some type of electrical sensor on the back of the pump. I have been searching for info on removal of the pump but nothing is coming up with the removal of one of these.
 

Shiny

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Update:
I replaced my power steering pump with a new one, this time I got one with the EVO bypass pipe. It works beautifully now.
Something was definitely wrong with the EVO Sensor on the back of my power steering pump. It was causing me to have no owner steering or such a small amount that the pump would just wine.
 
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