Mechanic told me one of my calipers has gone and this caused accelerated wear to relevant pad and all that's left is metal. You can see only metal in the pic 1 of pads as compared to the good brakes in pic 2.
1) I didn't understand why he said the caliper needs replacing. All I remember is he said 'look the disc on that one is red'. From the bad pic can you explain what's wrong with the rotor and if it does indeed need replacing? why did he point out that it's red?
2) All other discs, calipers and pads are fine. With the faulty caliper due to metal screeching on the disc, there are two circles lines which I can feel going around the disc when I put my finger on. Maybe you can tell in pic 3. Does this rotor need to be replaced? I will probably sell this car in a 1-3 months and have spent endlessly on repairs so I'd rather not buy the caliper unless it's really required even though I know their cheap.
Edit: yes, this question is about the rear left caliper and disc shown in pic 1 and 3. Pic 2 is rear right caliper which I imagine is fine. Also the answer isn't clear to me.
I understand one pad is worn so I will need to change back two pads for balance, but why all 4 pads? Also does the brake disc even need to be replaced(is it a must or just recommendation) and if so is it just the one I need to change, if more why? Is it just the one caliper that needs to be changed, or can I keep it and just change the pins on it as somebody mentioned? please clarify.