Hi Guys, I need some HELP!

So I failed a Warrant of Fitness for 'Unbalanced Rear Brakes'. - Right Rear is '140' vs. Left Rear '200'.

I've had a weak handbrake on the Right hand side for a while (it was hardly grabbing) and figured something had gone wrong in the Caliper.

I then ordered a fitted a 2nd hand Caliper to replace the (what i thought was) faulty item. Followed bleeding procedure, LF RF RR LR...

This did not fix the problem however, the brake bias was relatively unchanged at 160 vs 200.

I then thought perhaps the calipers needed rebuilding and regreasing.. I took both off the car, rebuilt and regreased both. Both were identical and non-faulty.

I ended up re-fitting the original Caliper (as both were non-faulty, identical apart from one having a bit of rust around the piston dust-boot.) My handbrake now works great..?

Went back for a re-inspection and the bias is still 140 vs 200. I'm guessing this has basically eliminated the Calipers as being faulty. The rotors are good, no pitting or scars etc..

I've checked the brake lines - no leaks, theres no leaks round the master cylinder or abs unit...

My real question is where to now..? the workshop manual is pretty vague about proportioning valves... Is that what could be wrong??? Can I access it?

Thanks in advance guys

 

Here in the states we don't have anything like the UK MOT inspection. Here they only even inspect cars that are more than 10 years old, and then only test if your horn and all your lights work, and male you apply hand brake and make sure your car stalls before moving when you let out the clutch (or hear rpms go up on an automatic). They make sure there is no visible body rot, but don't check uderneath at all.

So the concept of testing brake bias is foriegn to us. Even shops don't have equipment to detect this. No place other than maybe a race shop where we could have this checked if we wanted to.

So there won't be a lot of answers from experience from this side of the pond. Hopefully someone on your side has experience, or someone knows from theory.

 

Are the brake circuits diagonally linked? I think most cars are like that now. So, if you lose all line pressure in one caplier, you won't lose an entire axle.

I would look into seeing what component is responsible for this behavior and examine it.