How to change this type of Rear Brake PADS with this Caliper? - UK 2004 Prius Gen 2

I haven't been following the political details of whether UK can still get to the repair manuals on toyota-tech.eu or there is some other place one has to go now.

The thickness of those pads looks just fine to me. If I had everything apart that far, I would continue and just take the calipers off (keeping the hose attached), clean the rust off the pad pins and other surfaces the pads slide against, see to it that things move freely.

Obtain rubber caps for those bleed screws. There's an open passage through the center of a bleed screw, meaning when left open like that it will rust securely into the caliper from the outside and from the inside, sometimes becoming impossibly stuck. My first Prius was, I think, my first vehicle that I remember coming with rubber caps on the bleeders, which struck me at first as an extravagance, but it means bleeding the brakes goes effortlessly every time.

I still remember the wars I had with bleed screws before that. Sometimes I eventually managed to get one out. Once I took the whole wheel cylinder off and got the bleeder loosened by a guy with a torch. Other times I simply broke it off and ended up replacing calipers that were otherwise just fine. For a while I had one bleed screw that I kept after finally getting it removed and without damaging the caliper. I might have a photo of it somewhere. You could barely tell what it was. The end was pounded flat by the efforts I had needed to get it loose.

The rubber cap makes all those adventures go away.

I suppose it might be a little past time for the bleeders I see in these photos. It might be worth trying (moderately; give up if you would have to struggle or risk breaking it) to get those open and, if you can, replace them with new bleeders, and rubber caps.

 

That site is still linked from Toyota (GB)’s page (click the Find manual button under Repair Manuals, lower right), and in any case, you don’t have to be in Europe to subscribe, as long as you can pay in euros.