Micra rear brake load compensator

You could do worse than using something from this selection... you might need to be able to run and flare your own brake lines etc to do it, but that's not that hard. And it's a whole lot cheaper.

I've got flaring tools, but the guy at the MOT station insists on the genuine item. Anyway, I've since found out the valves in the compensator are free, you can remove them. Or at least you can remove a nut and the rod it retains, which has a spring and a seal. It's possible there might be a piston in there too, but I can't see anything with the compensator still on the car. I had no problem bleeding the brakes when I put them back, but there's still no brake. The shoes are free, as is the handbrake cable, the cylinders are OK.

It's puzzling me why I can bleed them easily enough, and get a good pedal, yet the brakes still won't work. Well, they will very slightly, but it's far from enough. I'm obviously missing something, I just wish I knew what.

HFM? I don't know how similar it is the one on my Alfa (a Bendix one) but I can get a new one for about 60quid.

To be honest, as long as the piston and the arm are all moving smoothly, I don't see how it would be broke. I'm assuming it's failed on the MOT? On what exactly? Broken linkage?

When you say the brakes no longer work, do you mean just the rears or the front too?

I'm not sure that he has the right to insist on any such thing. Obviously I could be wrong, but my understanding is that _if_ a compensator valve is fitted then it must be free of leaks, but that is it. Your insurance company might not like you using a variable compensator without telling them about the mod, but it's got nothing to do with the MOT man.

The message from curls contains these words:

Eh? It's not his decision. As far as I know, pattern parts aren'y yet outlawed. Provided it's secure and not leaking it's not is problem.

It's not just because you've got the rear suspension unloaded is it? If you have the wheels dangling free then the brake compesator should just about cut off all the braking.

Tim

Looks dodgy to me but I know v. little about these things. Surely a non-load compensating valve would be a bad thing in a road car?

Tim

The message from curls contains these words:

Generally get hold of the actuating lever and waggle it up and down for a few minutes.

Then put 3 sacks of potatoes in the boot & drive down a bumpy road.

That doesn't help for a Micra though. :)

It failed on the rear brakes not working. After checking everything else, I put it down to the load compensator.

Just the rear.

Sorry, I meant he insists on the compensator being there. By genuine, I meant there doesn't appear to be a pattern part available. Badly worded on my part.

I tried it all ways possible; jacked up under the suspension, under the body, with and without the arm in place, with the valve plungers held at various positions. No change at all.

I'm a little unsure about how it actually works. The springs inside, controlling the plungers/push rods - whatever they are called - hold the plungers fully in, so waggling the lever while the car is stood will have no effect. It seems to me that pressure from the brake pedal will push the plungers down - they are fully in normally - then the attitude of the car, and hence the lever, will affect how far down the plungers can travel. So, if I'm right, and uncouple the lever, the brakes should work as if the compensator isn't there. But it ain't happening.

are you sure its the compensator and not the master cylinder? correct me if im wrong but dont the master cylinder operate the wheels two at a time? ie.. the master cylinder has two pistons... each piston operates two wheels? maybe the seals on one piston are starting to go. thus it pushes fluid when bleeding but not when under pressure? so the good cylinder gives the peddle firmness when it stops two wheels but will not work on the others??

is there anyway he/she could check the pressure of the fluid whilst breaking??

No, it was just to illustrate how much they're taking the piss.

You mentioned that you've bled the brakes. I'm assuming that you're getting fluid out of the rear calipers/drums then? If so, IMO I'd be thinking that the valve is fine and the problem is elsewhere.

If you're still convinced it's the valve, perhaps it's worth bypassing it temporarily with some made up pipes just as a test.

The message from curls contains these words:

Quite possibly true, but it's worked for me many times.

This article may be helpful.

Problem solved, it's going to the scrappers. She decided the problems with the brakes, on top of the cost of the welding that's needed, just isn't worth it for a K reg car.

Thanks for all the replies.