So I have a 1973 John Deere 410 TLB that needed the accumulator rebuilt. Power steering worked great beforehand. I pulled it, rebuilt it, and assembled it. I thought I added enough fluid after and clearly spaced it. I started up and shortly after lost all power steering, manual is fine. I was down 2.5 gallons. Added the fluid and the hydraulics operated smoothly and wonderfully. The reverser works great, trans shifts fine, Loader/Backhoe work fine. Still no steering. Thought I'd lift the nose up and work it back and forth, no change. Then I started to suspect a little piece of paper towel was left in the fitting for the accumulator. Pulled the hose, did find a tiny piece on the accumulator side of the steering hose. Stupid me. Nothing inside the hose, pulled the elbow at the end too and that's clear. Could something have worked it's way further down somewhere? I was thinking maybe the sump screen clogged up? Would that take out ONLY power steering though? I hate pulling that and having to put 20 gallons/ $240 in the machine only to find the screen not packed. I'm assuming it will all drain out or does anyone know how much needs to be replaced in that instance? Would a clogged screen or trans filters take out only the steering system? Is it possible that I'm over chasing that idea and the steering system is just somehow airlocked? Should I do some kind of bleed procedure? Any advice is greatly appreciated. Thanks!
It has a steering priority valve. I'd guess there is a likely place to start.
I ended up chasing further down the line and found a piece of blue shop towel jammed up in the check valve. I pulled it apart and steering came back! I didn't realize that check valve came out independently so that was a pleasant surprise.