I have a '93 Micra which has just failed it's MOT test. The mechanic told me the braking at the rear 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.
ps I just called the garage and the mechanic said the valve should be seen to move if **someone presses the brake pedal**. Is this correct? AFAI can see the mechanism operates because, under braking, the rear end starts to lift, the valve operating lever is compressed and operates in turn the internal hydaulic valve. This clearly DOES happen. How on earth it's meant to move/operate simply by pressing the brake pedal with car is stationary is beyond me! (Well many things are I suppose :-) )
Thanks.