I have a problem with my mk2 hatchback. After replacing the pads and discs, my driver's rear wheel is braking and it gets quite hot while driving. So the brake caliper and hose were replaced. The problem still persists. The system is probably not pressurizing because there is no pressure when the valve is opened. The handbrake is disconnected, it won't be that one, the brake is bleeded and the guides go easily, I also tried sanding off the pads guides. Please advise if anyone had something similar. 😩

Does the disc/hub turn freely when the wheel is removed and also with the wheel fitted? Would wonder if the caliper is dragging one of the pads on the disc while you’ve not got fluid pressure which would usually cause it to centralise itself on the disc?

Bit confusing you say the brake is bled but you’ve got no pressure when the bleed valve is opened?

Yes, you're right, it's confusing when I push the piston (twist) when installing the discs, the pads have a gap between the disc, so the wheel turns easily, but after braking, when they lean against the disc, the inner pad stays against the disc. By that fluid, I meant that the system does not behave like a one-way valve that pushes the brake fluid into the wheel but does not return the pressure back, so the wheel remains braked.

In the past, I have had this type of caliper stick due to the aluminium body corroding where the rubber bushing for the guide pins goes through the caliper body. This causes the bushing to pinch on the guide pin, causing the brake to drag.

I have successfully removed the rubber bushing, cleaned up the corrossion, and reassembled using plenty of red rubber grease to stop water ingress starting new corrossion.

I've just re-read your original post, and see you have changed the caliper. If you replaced it with a used one, then it could need the treatment described above (of course, if you fitted new it shouldn't be this, in which case make sure the pads are really free to slide in the support frame).

For those who have a similar problem, I removed some material from the new pads (1/3) and the brakes come back as new. It's a big mystery why it's like that, but the result is more important to me now than why it's like that.