91 Suburban 6.2L Diesel Power Steering/Brake Booster Plugged?

Have a little bit of a story to tell and wondering if anyone has experienced their power steering and hydroboost hydraulic system having a blockage in it.

TL;DR I replaced the steering pump due to sluggish performance when warm, solved the issue after I finally got all the air out. A week later, I lose power steering and brakes and the engine turns over sluggish because the steering pump is apparently heavily loaded all the time.

I recently did some front end work on my 91 Diesel Suburban, and decided to replace the power steering pump since it was weak at idle and that kindof got old. I guess I was feeling motivated because it’s not like it was undrivable. So of course, I order a reman pump from Rockauto with the reservoir, but the return tubes are just the wrong ^&%$# angles and interfere with the bracket, so BBB has not impressed me. Got another one from them, was able to make it work as the deviation was not quite as large. Got everything put back together, jacked up the front and and steered lock to lock about 20-30 times purging air from the system. I did try for vacuum bleed after but my rigging up a cap was less than successful. I had also flushed the system prior to changing out the pump with fresh fluid, perhaps I didn’t put enough through it. Replaced the return hoses & fill can hose, but left the pressure hoses as they were (perhaps this was a mistake that contributed to the current problem).

Anyway, power steering wasn’t much better after the job. I drove it around a bit and held the brake down to help purge air out of the brake booster, which seemed to do the trick and now I could steer at idle with a warm power steering system for the first time in as long as I can remember with this truck (maybe ever since my father bought it).

Then about 5 days later, I drive the truck for some errands, it’s been fine all week and been driving it. I leave the first place and notice the motor turns over pretty sluggishly, and with an old 6.2 diesel that’s gonna kill your chances of getting it started. So whatever, I drive it to HD because I wanted to put 800CCA batteries in it and swap the old ones it had over to my 85 diesel suburban which has none. Starts sluggishly at HD too, and then I notice my power steering and brakes are….. marginal. Drive about 500ft over to a fast food place and they’re completely gone. It’s all manual baby!

So, I figure there’s a blockage in the power steering/brake booster loop. That’s my best guess on why it suddenly cranks over slow when warm, when it cranked over and started just fine cold when I left the house! The pump is constantly loaded, and I hope driving it 6-7 miles home didn’t kill the pump, but based on the fact that it’s still loading the engine I’m gonna go with “maybe not”. I still need to push it into my garage, if it started sluggishly when warm, a cold power steering pump at max pressure might just make it impossible to start unless I wanna get under it and loosen the belts.

Have the power steering tester kit on the way that Eric mentioned, because I’m not about to start throwing brake boosters at the darn thing without knowing where the problem is for sure (and what condition the pump is in). Those aren’t cheap, and chasing a problem in circles is just going to cost me more money. My current theory with the hydroboost being plugged is based on neither power brakes nor steering, and the hydroboost is first in line for hydraulic pressure. They have separate returns, and neither function is experiencing assist. Either that or the pump itself is blocked, I suppose. I should be able to figure that out with the pressure tester tool.

I’m concerned about the apparent blockage though, if there’s junk in the brake booster, is there any sense trying to mess around backflushing it to see if I can clear it out? Or is anyone familiar with this type of failure mode and perhaps an alternate cause for this issue on these units? Or is this a known failure mode on a steering pump? I guess my theory for a blockage would be old pressure lines depositing junk in the system.