Has anyone drained and flushed the engine fan fluid (it's a hydraulic fan, very rare in cars according to a mechanic)?

I need to flush it out and put new fluid in (cap says Dextron II). Any ideas? I put something I wasn't supposed to in there and need to get it out!!

Thanks very much for your help all!

 

sorry to bump this but my hydraulic fan is leaking as well and i wanted to know if anyone knew a way to drain the fluid... lexus said it was a gasket seal issue but i need to drain it first before i change the seal. thanks in advanced everyone