R50 handbrake - one side not working?

[Pitre]

Just failed an mot because handbrake one side is not working at all. Guy reckoned the caliper was probably seized, but surely the foot brake wouldn't work if that was the case, or am I being dim? This is not my car (belongs to the Mrs) so I've not looked at it before.... Advice please?

[E-bmw]

Could be a few things including but not limited to:

Handbrake cable, handbrake mechanism, caliper.

You need to either take it somewhere or get under it & check it all out.

[CarsOrBikes]

this is likely to be either a cable stuck due to rot in the guide tube leading to the caliper which can sometimes be freed, look at the caliper and see if the linkage is sitting on the return pin with the handbrake off, obviously you'll need it in the air a bit. If the linkage isn't it can sometimes be pulled up with the aid of a suitable lever and with the assistance of another you can try to get some oil slowly down the cable guide by lifting the bellows over the exposed end, use the assistant to operate the lever in the car and upon release apply leverage to retract the caliper linkage, you may have to do this about twenty times,

if it fails, renew the cables, yes both, they're inexpensive even for genuine really and a pain to release in the car so for that reason alone it's best to get both done as you're in there

another issue they have is that where the guide pins pass through the rubber tube guide, they pinch due to corrosion inside the caliper, pressing the tube against the pin, use a small screwdriver with the pins removed and caliper off, to prise back the boot in a few places and get some lube down there to free the tube and allow it's removal without damaging it, then when out scrape off all the white powdery rot, grease the tube etc and refit and reset the caliper, ideally a few times to gauge if it's also tight, if it resets ok the car just needs the brakes resurfacing and bedding in.

test the parking brake balance by reversing the car and applying the parking brake to stop you, both sides of the car should lift simultaneously, if not do more work on the brake linings if required or renew them, often the discs are rotten from low effort use.

not always a caliper ;O)

or bring the car to me of course....