E30 front brake calipers

one front caliper is not releasing fully.. binding and squealing. 70k miles up on an 1993 car, ABS and vented disks.
whats a likely casue? rusty cylinder/piston?
is it nessessary to replace both front calipers as a pair, even though the other one works fine?
all new front disks, pads and full fluid change going in when i tackle it.
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Hi Keith, I found the same with one of mine on the E30 last year. Turned out to be a partially seized slider due to the rubber boot having split and let water and dirt in. I dismantled and cleaned it up, and rebuilt with lithium based grease and a new boot. Did the other side too for peace of mind. It's been fine since. If you take the pads out you'll be able to feel by hand where it is seized. Get some threadlock in before you tackle the job, you need it for the slider bolts. -- Mark
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