Rebuil my PS pump (Saginaw pump, used in a lot of gm vehicles).

[davester]

Prelude:  This is mostly a hints/tips/warnings post, not a step by step procedure of what to do.

 

The PS pump in my truck has been groaning/whining louder and louder over last couple of years, most likely due to the return line popping off the steering gear port occasionally.

 

It's weird, middle of winter, I'll go to leave a jobsite to go to the next one, and the steering gets hard to turn, and the hose will have popped off.  It's got good, clean PS fluid, new hoses, originally used the spring clamp, switched to a worm-gear clamp, now have a bolt-style & worm gear clamp on it, the fitting itself is fine and undamaged.  Put the hose back on, refill with PS fluid, and everything works fine, until the next winter, when it's cold out (ie, -25C or colder), and sometime while going from spot to spot, the hose will pop off when I start up the truck (I suppose it's possible it comes off when I turn the truck off, but it doesn't come off while driving around).

 

Anyway, the pump was making more noise, so I got a used pump from a '08 Sierra, so it has what is supposed to be a bit better pump (12 vanes vs 10 vanes in older pumps like my truck has), Got an ACDelco PS Pump Rebuild Kit (#36350390), installed the kit in the pump, then installed the pump in my truck.  The kit included the shaft bushing, probably wasn't necessary, but the kit isn't much cheaper without it, and if you are going to take the whole thing apart, why not replace one of the wear parts...

 

Sorry, no pics or videos, but there are plenty on youtube and elsewhere describing how it all comes apart and goes back together,

 

First, a warning about doing this at all.  There are two parts that were damaged disassembling the pump.  The retaining clip (this holds the rear cover of the pump in place) bent pretty badly from driving in a punch in the hole for removing it.  And then, the rear cover bent and cracked from hitting the PS pump shaft to drive that rear cover out.  Maybe I just got unlucky, but if it was the pump out of my truck that I was hoping to rebuild and reinstall right away, I would have been screwed.  As it was, I have a '06 Sierra as a parts truck, so I got the PS pump out of that one, disassembled that as well, and the retaining clip didn't bend as badly, and the rear cover didn't appear to bend at all, so I used them  for reassembling the pump.  So, if you plan to do this to your daily-driver (as in, you need it to work right away), get another pump or two from a junkyard, rebuild one then swap it in (still should be cheaper than buying new, but not as much)...

 

Second, at least on my truck (a GMT800), it absolutely sucks getting the pressure line in and out of the pump with the pump installed in the truck (learned from when I replaced all the PS lines a couple years ago).  It has to be dead-straight in, there's not much room to get your hands in there to do it and see what's happening.  So, instead, I went for removing the bracket the pump is mounted in.  Removed the alternator from the bracket, then unbolted the bracket from the block, and the bracket on the back of the PS pump (also from the block, not the pump), disconnected the two return lines (two because I have hydroboost, these are easy to remove), then lifted the bracket/pump assembly up about a foot where I could easily get a wrench on the PS pressure line fitting to remove the line from the pump.  Then, on my workbench, I removed the PS pulley and brackets from the pump, and worked on the pump itself.  Did the same when reinstalling, and that was MUCH easier to get the fitting lined up right to screw into the PS pump.  As a bonus, didn't have to work lying on a concrete floor, with PS fluid dripping on my face.

 

Third, I had to redo all the work a second time.  The first time (rebuilt the pump, then swapped in my truck) it just didn't work at all.  No assisted steering, no brake assist.  Pump didn't make any noise, and was spinning fine, just didn't work at all.  Take it out, and take it all apart, and the only thing I can figure went wrong, is the pressure plate got hung up on it's o-ring, so PS fluid could escape out the "end" of the pump, instead of getting pressurized.  I could feel the drive shaft being able to move in/out of the pump more than 1/8" when I was taking it apart, which seemed excessive to me.  Reassembled it, making sure that pressure plate wasn't hung up on the o-ring, and after assembling the pump, I pushed in the shaft, which pushes the pressure plate into the spring, then quickly released it, a bunch of times.  Doing this there was only a small amount of in/out play in the pump shaft, maybe 1/32", similar to the play in the pump I took out of my truck.  Reinstalled, and this time, the pump did work.

Forth.  With the pump finally installed and mostly working, it still wasn't perfect.  When I started driving around, I noticed when the engine was idling (so low-speed turns), there was minimal assist happening, but once the engine was going a bit faster, everything was working fine.  There was no sound associated with it, just not getting an assist from it.   I decided to just leave it, and if it was an ongoing problem, I would swap back to the original pump (it was like 3AM, and I had to use the truck for work later that day), went to sleep, and after driving around a couple hours later that day, this low-speed problem went away.  I can only guess that maybe the pressure plate still was a little too far away, so fluid would escape out the end at low rpm, but at higher rpm, the gap wasn't enough to allow the higher volume of fluid to escape so enough pressure would get generated to get assisted steering.  I've driven the truck a bunch since then, and the problem hasn't reoccurred, so now I have a quiet, working power steering system.

 

To sum up, this is not something I would recommend for most people (rebuilding a saginaw pump), as between the specialized tools (bushing driver, PS pulley puller/installer [yes, I know you can borrow them as well]), the possibility of damaging parts that you can't buy (the end plate and retaining ring) requiring getting another pump for parts, you are only ahead vs buying a rebuilt pump if you are really strapped for cash.

[davester]

And, just remembered this, after reassembling the pump the second time, I decided to bench test that the pump would actually work, so I added PS fluid to it on the bench, not lots, just enough to cover the pump, put in the stud from the PS pulley installer/removal tool, along with a nut to jam it in place, then used an impact driver to spin it.  I believe I had to spin it counter-clockwise (reason for the jam nut), and get it going at a pretty good speed.

 

I used my Rigid 3/8" impact wrench, and very slowly ramped up the speed (accelerating too fast, it goes into impact mode and the stud comes out, even with the jam nut), and eventually the speed got high enough for the vanes in the pump to start working properly and send fluid shooting out the pressure port.  It was a mess, but it would have sucked more installing the pump and then finding out it still didn't work.