Hi Chaps, just failed the MOT because of the service brake efficiency. The tester said brake balance was ok, but overall 48% efficiency is a fail (50% req'd!)

So what does this mean?

He seemed to think it might have been a back caliper not working hard enough.

What can I do to sort this?

The calipers have recently being refurbished, with new dics and pads. The fluid was also changed, but I have had the brakes very hot since and got a very soft pedal at the time. Once cooled the brakes seemed ok again.

Could it just be the fluid?

 

Cheers Chaps....

 

 

BTW it breezed through the rest, which is always nice!:)

I'd try changing the fluid anyway. Could be a bubble in the system.

 

Peter

I would check the pistons in the calipers - seized pistons are a common problem.

 

The fronts do most of the work & these are most prone to seizing, so would pay attention to these first

if the pedal went soft then you've probably boiled the brake fluid, You should be able to just drain the discoloured fluid f till it runs clear and top up.

 

..but as above, pull the front calipers off and check the pistons move

Is there any pull to the side when braking?

Is there any pull to the side when braking?

 

No, the brakes SEEM quite OK, as far as the stock brakes can seem anyway!

No, the brakes SEEM quite OK, as far as the stock brakes can seem anyway!

 

stock brakes are actually not that bad when working properly!

If it has seized pistons the chances are the fronts will have an inbalance.Seen this loads of times when doing zed mots.you sure the guy didnt forget to put the rear wheels had locked? It realy isnt hard to reach 50% efficiency.Its calculated by dividing the total effort in kilos by the weight of the car.

Thanks for all your help Guys.

I replaced all the fluid, remove all the pads and gave them a quick sand, exercised all the pistons and took for retest......

 

PASS!! :clap: Tester said brakes were a lot better, couldn't give a %age reading as when they pass, its just a pass result on screen.

 

Said the rest of the car (apart from the smokey tubs!) was like new!:taz:

I would say the biggest part of the problem was the fluid, think I had boiled it at some time.

He shouldn't be doing it on the rollers due to you having a limited slip diff, he should be doing a decelerometer test instead, sounds like your tester hasn't got a clue to be honest.

He shouldn't be doing it on the rollers due to you having a limited slip diff, he should be doing a decelerometer test instead, sounds like your tester hasn't got a clue to be honest.

 

 

as above, will nacker the diff eventually, same with 4x4 most of the time too,