Front disc rotating tight / front brake pistons doesn´t release

When I switched to new tires and had the car jacked, I found the front discs rotating very tight. So I tried to push back the pads, it was hardly possible, just that could be accepted to run the car without overheating the brake. So I supposed that the rubber brake tubes will be swelled and constricting the flow, I even had this issue on an old VW from the 60s. Once the brake pedal is pressed, the pressure is high enough to operate the brake, but when released, the lips of the seal ring won´t apply the force to push back the piston against the reduced flow through the constricted tube. Happily, I´ve got had a set of steel brake lines and that was the opportunity to fit them right now, so I removed the old ones. After removing, I immediately was able to push the pistons back without any effort and fixed the new lines.

I was courious about the inside condition of the rubber lines, so I´ve cut them in about 6 oder 7 pieces to confirm the flow restriction - but I found none....the cross sections were open, no restricton present. I didn´t bleed the brake yet, no time avaliable, will do it the next days. But my question: What could restrict the flow of the brake lines if not the rubber lines? What would the pistons causing no to get them pushed back? Any ideas? Both sides the same issue !

The inner liner separates/collapses and creates a check valve of sorts. You won't find it by cutting it apart , but you can find it in a test lab where you can flow both directions.

What condition are your calipers in might be time to replace them . You can get rebuilt ones for a reasonable cost .

It is possible the pistons are hanging on a small rust or dirt spot on the cylinders.

If both front brakes seem equally tight (partially applied), crack open the bleeder, and see if it immediately spins easier. If it does, then indeed it’s a brake system issue. If the rotor still feels tight, clean the slides & make sure your wheel bearings aren’t too tight. If opening bleeder screw does ‘fully release’ the caliper….check to see if there’s an issue with the master cylinder, or the pushrod. The odds of both front brake hoses failing internally, the same way…..at the same time are million to one

I have fixed the problem in the meantime. It were the brake linings, I replaced them by steelflex linings, now the wheels are rotating freely and the brake feels better to control. Calipers were no issue.