Redraptor141
Thanks for the advice. I'm usually pretty gung ho about trying to fix things but I'm none to sure if venturing deep into the hydraulics of power assisted steering is a good idea for someone with limited experience in hydraulics. Seals and such like yes. Valves, seatings springs et al not so sure given the specific failure and lack of test gear. Two tons of P38 suddenly deciding its not turning right at motorway speeds could be .... terrifying...at best!
Looking at the sectional diagram in RAVE I'm pretty sure I know what the problem is. There is a bypass valve in the piston head open circuiting the power assistance just before the steering goes to full lock so the last bit of movement up to the locksteps is manual only. So if the steering is set right its nigh on impossible to hit the stops! The valve comprises a pair of balls sprung loaded apart in the piston head which are pushed by pins as full lock is approached. One pin in the body whose protrusion is set by screw adjustment and the other on the end of the recirculating ball screw worm. My diagnosis is that when dealing with the drag link, which really, really didn't want to come off the drop arm I pulled the steering right over to the end of the right hand travel so the ball got pushed further than it had ever been before and got stuck. One of those shouldn't ever happen but did things.
Right hand lock valve seems to be the one pushed by the pin on the end of the worm screw. So theoretically pulling the body mounted pin, pushing a slim drift in and tapping the other ball ought to shift the stuck ball. If that actually is the problem! Could also muck things up good and proper by coil binding the spring, podging up the seats or even worse. Not going there!
Anyway I have this brand new Britpart steering box to go on when I can get the steering arm off mine. Twelve ton ram in the puller set isn't working so this weekends job is to replicate the Sykes Pickavant screw pusher assembly with internal drive rod https://www.sykes-pickavant.com/products/suspension-tools/ball-joint-removal/1579 and put that in the puller kit.
Interestingly the Britpart pattern steering box has a ZF Made in Germany label so quality should be up to scratch.
Clive