brake efficiency

Hi all,

Just been looking through my paperwork etc for the disco and found my last mot advisory page (orange) and one of the things on it says

Brakes Advisories: RBT Service Brake Efficiency: 50%

and then further down says

Service brake Your vehicle has only just met the required service brake efficiency. It would appear that the braking system requires adjustment or repair [3.7.A.8].

Sounds like it only just scraped a pass on this one - but what does it mean and how do I fix it? Anyone?

Cheers

pop the wheels off and check the condition of the brake pads.. with age and use they can go brittle and lose their effectivness. check the disc's for excessive wear or pitting and grooves. when was the brake fluid last changed, should be changed regulary as again with age it gets contaminated and introduces a spongy performance.

Lee

Thanks Lee. I know the brake fluid hasn't been done while I've had the disco, and that's been 18 months, so it's probably due a change.

The master cylinder could be past its best, this also gives a spongy feel to the pedal. You can by a repair kit, but i would go for a new one if needed.

Is the service brake not the handbrake?

Dunno, that's partly what confused me - the wording sounds all wrong to me but I copied down exactly how it was written on the paper.

I know the handbrake is ok anyway because I parked on a very steep slope recently and the disco was still there when I got back!

Service brake is the footbrake. Front brake readings for a Disco on the Roller Brake Test normally give a reading between 350 / 420kg per side but the rears can be a slow as 100kg to a figure to give a pass around 175kg per side. The normal problem with Discos / Rangies is that they never carry enough weight in the back of the vehicle to let more brake fluid pressure through the brake compensator resulting in corroded / pitted discs and worse seized or sticking pistons in the caliper. Buy the comment on your advisory sheet i would say that you have partially seized pistons in your rear calipers, easy enough to check by removing rear roadwheels and take out the brake pads one at a time to try pushing the piston back (having first sprayed brake cleaner around the piston area to remove any muck first). If the pistons retract ok check that the pads slide ok in the caliper. If the caliper pistons are at fault it is easier to fit a new / rebuilt replacement caliper than try and fit seals and pistons. One other tip is to present the car with a load of weight in the back, this will put more pressure to the rear brakes (we always have 2 x 56llb bags of spuds for customers to "buy" before there vehicle is tested, usually it is the small hatch cars that "buy" them)

ello stiggo where ya bin

busy with me photos and mot'ing all week (7 till 7)

oooh workin yer sel up ter mot me series eh

must have had a good week for Landies, 3 Discos passed, 2 Rangies passed, 1 Series 11a passed, 2 Geeps failed, 4 Mit**** failed, 3 Daihat**** failed, 2 Isu**** failed and 1 Frod failed (all 4 x 4's)

wot yer doin on sunday, me wiring is still waitin fer ya

about 6 hours welding on a Healey 3000

ah well, theres always next weekend

stig said:

Buy the comment on your advisory sheet i would say that you have partially seized pistons in your rear calipers, easy enough to check by removing rear roadwheels and take out the brake pads one at a time to try pushing the piston back (having first sprayed brake cleaner around the piston area to remove any muck first). If the pistons retract ok check that the pads slide ok in the caliper. If the caliper pistons are at fault it is easier to fit a new / rebuilt replacement caliper than try and fit seals and pistons.

Click to expand...

10 weeks later and I finally got round to having a look...

I think you were spot on stig, the pistons are in a mess. I think I might have made one of 'em worse too! The pads were stuck, but I managed to get one out finally and tried pushing the piston back into the caliper - wasn't budging.

Now I don't know if this was a dumb thing to do but I pushed the brake pedal a bit to see if the piston moved, and when I went to look at the piston, it had moved but had brought a couple of rings with it - sealing rings??!! It was a right b*st*rd to push it back in so I could put the pad back too.

The pads and discs have decent thickness left (guessing about 6mm and 12mm) but it doesn't look like they are being used very much - there is an inch around the edge of the disc that isn't being used (it's really rusty) even though it is covered by the pad area.

Conclusion - pistons are screwed, easist thing is to get new calipers, pads & discs?

Any thoughts?

you will find a caliper renovation kit is cheeper than buying the full deal.

piston's aint too bad to buy seperate either.

new pad's lines and piston seal's for mine came to just over 30 quid for the lot that's including front pad's too..

took about two hours from removing the rubber to replacing it.