What hydraulic fluid is used in a Koken Barber chair?

Answer 1

Use hydraulic jack oil, available pretty much anywhere - I used Johnson's, 1qt bottles are $7.99 at my local O'Reilly.

To fill, or replace, the fluid you'll first remove the seat cushion. It should just lift off. Under that there will be a hole in the center of the base, it may or may not be covered by a plastic cap or a screw on older models.

Remove the cap to access the fluid reservoir. I would suggest removing as much existing fluid as you can before adding more, to avoid overfilling the pump. You can find a suction gun at harbor freight for about $15 which you can use to remove as much of the fluid in the chair as possible, without having to disassemble the pump mechanism. Place your control lever in the full down position, this will allow clear access to feed in the suction tube, as well as assure the chair is fully "down" and thus the reservoir as full as possible.

Once empty, refill with hydraulic jack oil. Add one quart to start, and pump the chair up. If it gurgles while raising and before topping out, or when lowering, lower and add another 2-4oz and repeat the process until it makes no liquid noises when being raised, and doesn't gurgle or gush when being lowered.

If you add too much fluid, the seals may be damaged and/or the chair will be very difficult to lower after being raised. Also do not EVER use any oil/fluid which mentions "stop leak".

Answer 2

You can use type f Transmission Fluid found in any auto parts store.