A vote for ATE- it's a known quantity on these cars. Swap both of 'em to ensure no funky problems surface.

--- Rebuilding 'em is easy if you have an air compressor- just don't split 'em (you'll never get it to seal up right again) just replace the piston o ring and main seals.

PS if you try to rebuild keep your hand away from the piston as you apply forced air to the caliper- it will shatter your hand when it comes out.

rjp

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03 540I (GAK!!)
81 280E (W123)
70 LeMans Sport with pissed off Poncho 462"
1989 Silverado Step Side (under the knife- complete restomod)