[ainarssems]

My old D2 and also C4 A6 had weak handbrakes but it was mostly caused by the shaft that goes in calliper getting rusty and not rotating freely so that spring was not returning it fully and as the result self adjusting mechanism in the calliper was not working properly. A bit of penetrating oil, good exercise and it was good for MOT.

As for the O2 sensors I saw a nice video on youtube showing how to test them with blowtorch. If you hook up voltmeter to signal wires and heat up sensor with blowtorch then as you move flame around the voltage reading goes up and down. On a good sensor it changes very quickly and goes up to about 0.9V but on faulty it's slow to respond and max voltage is lower. While I was playing around after a while I noticed that even the faulty sensor started responding better so I heated it well up and for long time and it started working as it should again. It seams it was contaminated but after heating it up contaminants must have burned up and it was working fine. I never put it back in car so don't know if it would have worked well in car or for how long but interesting finding anyway.