The car has rear drum brakes and been having problems for a while with the handbrake not releasing.

I have completely dismantled both rear brakes, cleaned and lubed all of the pivot points, taken the edges off the shoes, cleaned out the drums, made sure that the cables are moving freely......and yet after being left for a week the n/s brake does not release and there is a loud clank as the drive of the car forces the brake off.

Any ideas please?

The back plate that the shoes are fastened to will be ever so slightly bent. It's not enough to affect the operation of the brake shoes but just enough to cause them to bind and not release. You probably find they stick worse when you take the handbrake off and then reverse.

Thanks. I assume that the fix is a new back plate? Is it easy to do?

Never actually replaced one myself, although I've had two replaced on different cars by a garage.

Depending on the design of the rear stub axle it is probably not a major event.

13 hours ago, unclesam said:

The car has rear drum brakes and been having problems for a while with the handbrake not releasing.

I have completely dismantled both rear brakes, cleaned and lubed all of the pivot points, taken the edges off the shoes, cleaned out the drums, made sure that the cables are moving freely......and yet after being left for a week the n/s brake does not release and there is a loud clank as the drive of the car forces the brake off.

Any ideas please?

I know you have said you have cleaned out the inside of the drums, but I also had an issue of them sticking, especially after damp weather and being left for a few days inactive. I 'fixed' mine, by (on a clear or private road!), driving at about 20mph, and pulling the handbrake on briefly, repeat a few times. Forcing the shoes against the drum interior and 'cleaning' them with friction.

17 hours ago, StephenFord said:

I know you have said you have cleaned out the inside of the drums, but I also had an issue of them sticking, especially after damp weather and being left for a few days inactive. I 'fixed' mine, by (on a clear or private road!), driving at about 20mph, and pulling the handbrake on briefly, repeat a few times. Forcing the shoes against the drum interior and 'cleaning' them with friction.

This^
mine were sticking slightly a few months ago if the car had been left more than a day without using it. I pretty much did the same as Above and the problem has gone away. 

On 4/9/2023 at 9:15 AM, StephenFord said:

I know you have said you have cleaned out the inside of the drums, but I also had an issue of them sticking, especially after damp weather and being left for a few days inactive. I 'fixed' mine, by (on a clear or private road!), driving at about 20mph, and pulling the handbrake on briefly, repeat a few times. Forcing the shoes against the drum interior and 'cleaning' them with friction.

Thanks for this - but in my case the car has rear drum brakes so every time the brake pedal is pressed the shoes contact the drums anyway. I can see what you are saying for cars with rear discs and I do the same as you to keep a BMW auto handbrake working.

7 hours ago, unclesam said:

Thanks for this - but in my case the car has rear drum brakes so every time the brake pedal is pressed the shoes contact the drums anyway...

My car also has drum brakes fitted to the rear. Yes, pressing the pedal may activate them slightly but the balance between your front discs and rear drums sees virtually all the work done by your front discs. 

Applying the handbrake ensures that the load is all put on the rear drums, especially with the weight of your car, and the fact that it is pulling it to a stop will ensure much more pressure will be put on the drums rather than just pressing the pedal. Still, it's your car, and if you don't wish to follow some widely proven advice, entirely up to you...

I still have a copy of the official Repair Information Manual for my old Rover 75. You might be interested to see this extract specifying the procedure for bedding in the rear drums before performing an adjustment of the handbrake:-

2 hours ago, mjt said:

specifying the procedure for bedding in the rear drums before performing an adjustment of the handbrake:-

Of course this procedure is no longer possible in the UK due to the following:

            "a road test should be on well surfaced, dry roads."

just where in the UK would you find a well surfaced road ? 🤣🤣

 

 

Quite difficult to find a dry one at the moment.

You say you've "cleaned out the drums" ??

Did you rough-up the brake shoes and inner drums with sandpaper as they have probably become glazed over the years....could be worth a try ??

Also, leaving the brake dust in there, rather than emptying it out, also helps with braking efficiency... (I worked for Mintex back in the mid-80's and contrary to what I had been told when I started mechanicing, we were told to leave the brake dust in there !!)