power steering issues

[Fossilfreefuel]

99 Suburban in our shop. Came in with weak power steering and lots of whining noise. We replaced the power steering pump and now there is no brake boost or power steering even after a bleed procedure. We swapped the EVO from the old pump because they are no longer available new. Maybe it's the EVO, maybe we aren't bleeding the system correctly. Any suggestions?
Thanks

[DmaxMaverick]

Hydroboost. If the pump was bad, it may have sent some junk (metal, seal material, etc.) to the HB unit, and now the relief or proportioning valve (both internal) is stuck (no pressure for assist). Disconnect the output line from the pump and connect it directly to the steering box (bypass the HB unit - CAUTION...High Pressure...use threaded adapters, not clamps). If steering returns, the HB unit needs replacement. If the pump grenaded (noisy, growling, grinding, rattling, etc, but not normal bypass/extreme throw sound), it's likely contaminated the entire system, and the steering box will also be effected (may not show it for a long time, but will likely fail at some point).

If the pump failed internally, a fluid sample should be tested for contaminants. Drag a magnet through the fluid first, then have it lab tested for pump material if no immediate metal present. Usually, there will be enough metal you can see on the magnet. If this is the case, the HB unit should be replaced (damage is done, and will only repeat or get worse), and the system should be fully flushed before AND after replacement (with a filter on the return line before the pump reservoir, a large metal -not plastic- inline fuel filter does well for this).

[rustyk]

I agree (mostly) with Dmax. Before bypassing the hydroboost, however, connect a clear 3/8" line to the low-pressure return, and feed it to a collector (jug, pan, etc). Start the engine, hit the brakes, stop the engine, top off the reservoir. Repeat. Whatever crud is in there may come out (if crud is the issue). This is the best method for totally bleeding the system, BTW, since the HB is the highest point.

What is odd is that there's no brake or steering boost. This would almost indicate the replacement pump is toast.