You will have to remove the caliper to avoid damaging your rotor when you open the pads. Loosen the top from the brake reservoir. Make sure you have a cloth or something wrapped around the reservoir because you are going to open the pads forcing brake fluid back into the reservoir and you may get some spillage. When you force the pads open, you should be able to tell if one of the pistons is sticking or stuck. It will take some pressure to open the pads up so do it carefully so as not to tear up your pads. Since this happened after being stuck in the rain, you will want to check the pad retention pins and make sure they haven't corroded causing the pads not to be able to release.
Other things to consider:
Collapsed Brake LineFlex Hose: The internal wall in the hose can come apart or wear out allowing the fluid to not release keeping pressure on the system.
Master Cylinder Piston: The piston inside the master cylinder may not be releasing. This situation is usually remedied by replacing the master cylinder.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
2013 FLTRU, Jackpot 2/1/2 Stainless Ceramic Coated Head Pipes, Fuelmoto Stage 1 Intake, Power Vision, Jackpot Full Size Ceramic Crossover, MADSTAD 16" Windshield, Motolight Running Lights, Nostalgic Rails, Airhawk R, Hayden Primary Tensioner, V&H Roland Sands Slant Slip-Ons