Last year I took my car for its MOT and was presented with a green form for a pass and a yellow advisory form listing things I should look at during the year. It said:
Rear Brake load sensing valve linkage stiff [3.6.E.4]
I had meant to look at this during the following 12 months. I really had. But I didn't.
This year I picked up a red form with some bad stuff on it starting with the word FAIL.
Among the grief was this:
Rear Brake load sensing valve linkage seized [3.6.E.4]
Or to put it another way, I hadn't bothered to look at the problem when I was told to so now it was coming back to bite me on the backside.
My first problem was I didn't actually know where this linkage was. A quick look in the Haynes manual, followed by a peek when the rear tyre was being replaced showed me it's at the back, on the drivers side (this applies to cars where the driver sits on the right, as God intended, where the thing is on other vehicles, I dunno.)
(Note: Car is on a 3 tonne jack AND and axle stand. Do not rely on a single jack when sticking you head under 1 tons worth of motor vehicle)
It's behind the wheel arch. You can just see the spring that connects it to the rear suspension. My understanding is that the linkage controls a valve that alters how much brake force is applied to the back wheels depending on the load you have. Put some fat blokes in the back seats and you get more or less brakes at the back. Not sure which to be honest, but that's not the point.
At one end there is a spring:
which connects to a lever. The other end of the lever wraps round the valve here:
As the suspension goes up and down, this lever should move a bit and presumably alter the position of a plunger in the box with all the brake pipes coming out of it. Mine had seized up solid thanks to its position under the car, right where all the wet and muck is.
Now what I should have done is sprayed it regularly with penetrating oil and then greased it up. That would have stopped the problem in the first place. Faced with a fail sheet, what I did was spray about half a can of the stuff over the pivots, spring, and pretty much anything else in the vicinity over about half a Saturday. Then I tried to waggle the lever by gripping one end with a pair of mole grips. This produced movement but not much and I wasn't sure if the metal was bending (bad as it could snap) or the pivots had freed up.
As it was I took the car to Geoff. There was a gaiter to replace as well and I wasn't in to this - VeeDubs are so much easier in this respect - and he's next door to the MOT people so I can be confident he will do the work to their satisfaction.
Geoff said that 2/3rds of the Peugeot 206's he sees with MOT fails have this problem. What he does is stick a screwdriver under the plate and waggle it about. If it's not too rusted, this will solve the problem. My oiling didn't hurt though and a future treatment will hopefully stop this appearing on the sheet next year.
Legal note: This is an accurate description of what I did. I am not a professional mechanic and these notes are offered for entertainment only. If you chose to follow them and things don't work, it's not my fault. Sorry. If you are at all unsure then get a professional to do the job.