MOT fail brake load sensing valve seized

[JamesMK]

Evening chaps, had my mot fail yesterday on the the brake load sensing valve and a few other bits that I have been sorting today. 

Ive managed to free up the arm that has a spring connected to it and it appears to move freely now, should this be moving when I apply the brake? Unsure how it works had a brief google and couldn't find much. 

Cheers

[geoff]

I've managed to free up the arm that has a spring connected to it .... should this be moving when I apply the brake? 

 No it works by sensing the vehicle load according to suspension height, the valve applies less braking effort with the vehicle unloaded and more proportionately more braking effort when loaded, make sense ?

[minisandfords]

I freed mine up for last MOT (mine is M49 but same design). If you have a big load in the back, it opens the valve so the rear brakes apply more effort. I could definitely feel the difference when the car was packed for holiday! Try driving it with a full rear seat and you should notice if it's working.

[JamesMK]

Thanks Geoff, that's helped me understand what it does.

I've had it moving freely now so hopefully all is good come the retest. I never really have anything "heavy" in the back to notice it tbh but I'll pay more attention on the next scrap run haha.

[brodfather11]

 "  Evening chaps, had my mot fail yesterday on the brake load sensing valve and a few other bits that I have been sorting today. "


That's a strange failure , unless the spring is fallen off or broken and even then some testers just ignore it.

If it was stuck in the lowest position it still should have passed. (See what Geoff said)

If it failed for low braking effort the problem may be the rear shoes/wheel cylinders or the rear flexible brake pipes , rather than the valve.

[Bertie]

Evening chaps, had my mot fail yesterday on the the brake load sensing valve and a few other bits that I have been sorting today. 

Ive managed to free up the arm that has a spring connected to it and it appears to move freely now, should this be moving when I apply the brake? Unsure how it works had a brief google and couldn't find much. 

Cheers

Removed due to spam complaints

[dumdum]

 "  Evening chaps, had my mot fail yesterday on the brake load sensing valve and a few other bits that I have been sorting today. "


That's a strange failure , unless the spring is fallen off or broken and even then some testers just ignore it.

If it was stuck in the lowest position it still should have passed. (See what Geoff said)

If it failed for low braking effort the problem may be the rear shoes/wheel cylinders or the rear flexible brake pipes , rather than the valve.

No it’s adefinite fail, if it’s seized depending on position you will get too much or too little braking effort to the rear, if a tester ignores it it’s his license on the line, not worth it, and every MOT tester I know of will either free it off or fail a seized brake biasing valve

[GraemeT]

Yup - our older Pug 'failed' on this and the nice man attacked it with WD40 and lots of wiggle before it was nicely 'passed'. That car never had anything in the back as it was t'missus' commute car so the thing would never get moved in daily use - hence it seized it one position.

[timpascoe]

Mine failed and when I came to free it, saw the spring was broken (very common). There is a good kit on ebay with excellent instructions that helps you understand the whole set up and even has photos of a quality that puts Haynes to shame.