Williston,
Sounds like there is a kink in yor discharge circuit.I had a 245 picked it up for $200.00 au. Solid car . I did a head so I gave it to the mines I was contracting to and they used the jaws of life on it to conduct mines rescue from time to time. Anyway this kink may possibly be where your tailgate hinges off the roof of the wagon.I had no power to my rear windscreen wiper and noticed that the electrical service was kinked and had severed over years of use.This might possibly be the same area where the fluid kink is as I am pretty sure the electrical runs alongside the fluid line.
If that dosent isolate the problem you might possibly have to exchange the whole rear fluid circuit.
Si850