I have a 98’ Lumina that does not have ABS brakes. The last few months, at random times, the front brakes will stay on, even though the pedal comes back up. My dad (self described backyard mechanic), has replaced the brake pads, roters, calipers and the master cylinder to no avail. When he pulled the master cylinder, it was totally caked with carbon gunk. Pulling over and pushing the brake all the way down seems to un-stick them for the time being. Any ideas what could be causing this issue? He’s hooked it up to the code reader and it’s not setting off any codes.
You probably need to have the front flexible brake lines replaced. They will often degrade on the inside. You can get chunks of the interior walls that act as check valve on the brake fluid.
If you can next time it does it open bleeder screw for 2-3 seconds on wheel that is sticking, if it then works you have a bad break line that is plugged.
Try replacing the front brake hoses. They are cheap and often overlooked parts that need routine replacement to keep the brakes working normally, and they usually produce these very symptoms.