A Mechanic describes the oil and nitrogen servicing of a CRJ-200 Nose Landing Gear (NLG) that he and another Mechanic completed prior to the aircraft being towed to a gate. The CRJ-200 flight crew performed an air turnback shortly after.

Narrative

I assisted mechanic 'X' with the strut servicing of a CRJ-200 aircraft. I was not immediately present when he released the air pressure from the nose gear strut Schrader valve. However; the strut was fully collapsed and did not appear to have any remaining air inside. Mechanic 'X' did comment that the Schrader valve did not seem normal. When it came time to service the strut with fluid it took numerous pumps; more than twenty to fill the strut. He stopped pumping the bowser when the strut began to lift off of the bottom of its fully collapsed position. He then capped the strut and serviced it with nitrogen to the correct extension. At the time; it seemed to be fine.In retrospect; I remember that when we filled the strut with air; it seemed to respond too quickly to the pressure suggesting that the strut might not have been fully serviced with fluid. This was noted as odd but we did not act upon it as I though that it might have been a problem or characteristic of the nitrogen cart regulator and he was still suspecting a problem with the Schrader valve. The plane was towed to the gate and no anomaly was noted. [Aircraft later made] an air turnback.