Problem- Bridgeport 308-SX Noisy, shuts down

[fredhh47]

I have a B'port 308-SX that was purchased new in 19xx. Since we bought it, we have replaced the Vector Drive, the coolant pump (Surprise! It's 460 volts, not 230, nearly burned out the replacement), the top bearings on the spindle leadscrew, the monitor, the control cable for the X-axis, and the LPM-286 motherboard. The vector drive and motherboard were replaced by EMI, very nice job! A bit expensive. I also later had to replace one of the DAC chips on the main control board. Had to buy 4 from a company in China for that deal. Also, the water soluble coolant dissolved the gaskets on the windows and some of them actually fell out. The waterproof work light wasn't waterproof and went up in smoke one day. It likes to eat fuses on the tool changer carousel and constantly has a problem with coolant containment. I love this thing!
Now, I have another problem with the Z axis, which may be another bearing problem, or maybe something else. The machine goes thru the homing cycle fine, but when I bring the head down to set a TLO and I am manually jogging, it appears to be moving normally, but makes grinding noises and then it will shutdown due to "Z axis overflow" or some such thing. If I try to run a program with the stored offsets, it will start the cycle, rapid and go into the feed move, then shut down with the same message. Has anyone had a similar problem, and what did you do about it? The machine is as good as dead as it sits. When she runs, she is a worker, but she has had her problems. I'd like to get it running again for the least cost.
Any suggestions?
Fred