98 Ls400 Power Steering Reservoir Spraying Fluid

[TimingSpd]

I posted this on another forum, but figured I could get some fresh opinions here as well. I've serached high and low, but have not found any record of a similar problem

To make a long story short, I had the motor and transmission mounts on my 98 Ls400 replaced by a mechanic (I was short on time), who also replaced an unspecified PS hose due to it breaking in the process.

I don't drive this car much, but the next few times i drove it I noticed steady plumes of white smoke on startup and for minutes after, which I attributed to the PS ACV (no visable PS leaks, losing small amounts of fluid). I replaced the valve with a stubby oil plug (shorter than the ACV threads). I then topped off the PS reservoir due to losing fluid in the process. Upon starting the car with the reservoir cap closed (bad idea), the steering made noise, so I opened the cap, at which point I was greeted with a intermittent, regularly timed spray (read: geyser) of ATF. I'm talking 6-8" plumes of fluid.

I've since removed the return line from the reservoir to test that the return is indeed coming from the return line (it is), but now I'm stumped. I'm assuming I was burning quite a bit of ATF from the ACV, and now it is simply being rerouted to the reservoir. Perhaps the mechanic reinstalled the unspecified PS hose incorrectly, but I'm not sure how it could be working enough to close the loop but partially blocking the flow. Thoughts?