So I recently (about a month ago) replaced a defective master cylinder with a rebuilt one, rebuild my rear calipers, new rear hoses and pads and rotors all around. Last week my brake light started flashing on while braking, so I checked and, sure enough the rear of the MC was low on fluid. I topped up and figured it was just from the pads bedding in or that I didn't fill it all the way up. Anyway, it was down to the min mark again today. I checked all four calipers, hoses, the rear hard line junction and around the MC and found no leaks. I'm assuming that when I pull the MC back I'm going to find plenty of fluid in the booster. So, when I suck the fluid out of the booster will I need to actually pull and clean the booster? Will the residual brake fluid cause any problem if I don't get it totally cleaned out? And most importantly, will brake cleaner f-up the booster?

thanks,
ben

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1985 300D 170k