so every once in awhile, my abs modulator unit (the hydraulic unit under the hood) like farts- like its trying to activate randomly just for a second. You can hear the motor "BRRRT", even when the car is just sitting idling. It doesn't throw any codes or anything related to this either, like it doesn't even realize it's doing it. Everything else in the system works fine, including bulb test and diagnostic modes.

Also, is there a procedure to bleed/fill the unit itself? There is what looks to be a fill cap of some sort and a bleeder, but the svc manual I have is for 98+ which is apparently different. My top reservoir is always low and I'm guessing there's a good chance these 2 things could be related