Leaking Front Caliper
 

So I am going to first state my issue then a long story. On my front driver side caliper I have a mysterious leak which I honestly have no idea where it's coming from. When the brake pedal held down fully depressed it slow leaks fluid. I think its coming from from the seal between the two halves of the 4 piston caliper or it could be coming from the hardline connecting point as fluid seems to be leaking from there and dripping down. It collects on the bottom most bolt of the caliper that goes fully through the caliper. I would love some advice to possible help locate the source. I really don't know if its user error or a fault from when I got them rebuilt by a shop. I recently had both front calipers rebuilt by White Post Restoration and through their testing they are stating that they're not seeing any leaks when they blow air through it as well as fluid testing. I'm really trying to get this done by May as there is a car show I already reserved a spot for on the Jersey Shore boardwalk. Any advice would be greatly appreciated

Story time. Back in January I wanted to finally do a brake job changing out the rotors and getting new pads, as well as flushing the brake fluid as I had no idea how old the brake fluid was (I bought the car back in October of 2022.) So I bought new pads and rotors, when they arrived I went to go put them on but my front brakes where seized really bad. On the front driver side only one piston worked when applying 100 psi of air, and on the passenger side 2 of the 4 pistons worked. I tried my best to remove them and gave up, so I sent them over to White Post Restoration as they were fairly close, they had a decent pricing, and a good non-transferable lifetime warranty. I sent them out in February and received them back in late March due to the pistons taking forever to ship. I put them on and had the mysterious leak happen, so I sent them back. When they tested them they couldn't find the leak I was talking about so I chalked it up to user error. Again I get them back and put them on and the leaks still there but this time my parking brake decides it doesn't want to live anymore.

If the rebuilder tested the caliper and found no leaks, check the hose connection.
Clean everything with brake clean, dry, then sprinkle talcum powder all around the area
and when the leak occurs you'll be able to see the trail.