As the prostate's function is to produce the milky fluid in semen and the seminal vesicles mix the sperm from the testes with this, once the prostate is removed there can be no fluid from this source. If you have a clear fluid it may be from the bulbourethral gland (or Cowper's gland).
"During sexual arousal each gland produces a clear, viscous secretion known as pre-ejaculate. This fluid helps to lubricate the urethra for spermatozoa to pass through, it neutralizes traces of acidic urine in urethra, and helps flushing out any residual urine or foreign matter. It is possible for this fluid to pick up sperm, remaining in the urethral bulb from previous ejaculations, and carry them out prior to the next ejaculation
This gland's function diminishes with advancing age. The prostate has nothing really to do with orgasm (other than supplying the fluid) Orgasm will still occur even if the prostate is removed.