Micra brake problem help sought

I have a '93 Micra which has just failed it's MOT test (UK). The mechanic told me the braking at the rea wheels is far too low. He said the "brake balance valve" would hardly move and that part alone costs £400ukp! Tomorrow he's going to try some penetrating oil and try to free it up. The other possibilty he said was the rear brake pistons could be stuck.

So, when I got home I put the car up on the ramps and took a look. All the levers I can see on the brake balance vale (which I now know is a load-sensitivce valve) seem perfect free to me. When I bounce the car up and down the valve spring gets compressed ok and moves the lever (which is under the rubber boot). Maybe there is another part of that valve that's stuck? I can't see anything else to "lever" free.

One more thing is that the car has been standing for 4 months over the winter - could this make either the valve or the brake pistons to seize like this?

Is there any way to be be sure it's the valve that's at fault - as it's so expensive.

Many tia

Just generally speaking, a car left standing for a long-ish period, the brake cylinders (inside the wheel-hub) can indeed seize up. 4 Months isn't "terribly" long though. Many cars sit idle for very very much longer without troubles

It's not "normally" a problem, but it does happen

If you have checked that load proportioning valve and it seems to be working now, then maybe that penetrating oil has fixed it.....if it was that, that was stuck

.....otherwise it sounds like it is those rear brake cylinders......NOTE I'm assuming here that the rear brake shoes and drums (or discs and pads as maybe) are actually in ok order

If the rear brake shoes (or pads) are nearly worn out then obviously that will cause poor rear braking

Again, assuming drum brakes, have a buddy (neighbour/wife etc) apply the footbrake GENTLY when you have a back wheel off and the brake-drum removed.

Meanwhile you're at the back of the car watching closely

You should see the brake cylinder push the shoes out-wards (CAUTION don't apply footbrake toooo hard because with the brakedrum removed the shoes may try to move outwards further than they normally could, when the drum restricts their movement)

This test will clearly demonstrate whether the rear brake shoes are being activated or not

HTH

Option 2 is ....move to the State of Western Australia, where so long as your car's licence renewal is paid promptly, there is NO regular roadworthy inspection regime.

Catherine Rural Western Australia