Rear Brake issue [Archive]

Northerner

22-04-2009, 20:39

Whilst preping the car for its MOT, i've noticed that the rear brakes are hardly working when the pedal is pressed, but the handbrake works fine.

Any ideas?

MAXIBOY

22-04-2009, 20:47

might just need stripping and clean and lubricating with red rubber grease.

might be a seized/wrongly adjusted load proportioning valve on the rear axle as they tend to be a bit rubbish.

Northerner

22-04-2009, 21:07

http://i36.photobucket.com/albums/e15/123maxiboy/DSCF3497.jpg

Looking at one of your old pics, is it the part that looks like a pedal that seizes?

MAXIBOY

22-04-2009, 21:11

yeah allows fluid to the rear depending on the weight in the car.

Northerner

22-04-2009, 21:17

Should I be able to push and pull the pedal thing?

MAXIBOY

22-04-2009, 21:30

yes mate should move back and fore freely..

northy

23-04-2009, 12:44

try and bleed the rear brakes. if you carnt bleed them its time to buy a new valve.

Amazing how well the rears work when this valve is new!!!!

Northerner

23-04-2009, 16:01

Have bled the rear brakes and they are better but not brilliant. I've also looked the the rear bias valve and it appears to be slighty weeping.

Can these be resealed/reconn'd or is it a trip to the stealers?

MAXIBOY

23-04-2009, 17:06

sometimes there's repair available..i got one..last time i asked there was nothing for many months..

but i think there stealer only parts.

Richardcard1974

23-04-2009, 20:04

Whilst preping the car for its MOT, i've noticed that the rear brakes are hardly working when the pedal is pressed, but the handbrake works fine.

Any ideas?

Try to find a friendly mot man who understands these cars. They nearly all have weak braking at the back due to the lightness of the rear of the car. The rears dont actually do a lot. The rears can easily rust over if you dont drive them hard once in a while.

Northerner

23-04-2009, 20:23

I shouldn't be able to turn the wheels with the brakes on abliet with a bit of brute strength, should I?

Also, I'm presuming that the calipers are ok as with the handbrake engaged, the wheels are locked solid or is this misguided?

MAXIBOY

23-04-2009, 20:41

no...usually the other way round..

if you pump the pedal up and hold it down do the brakes get better..

Northerner

23-04-2009, 20:43

Not really. They get better when the engine is running though.

Richardcard1974

23-04-2009, 20:46

Not really. They get better when the engine is running though.

Yeah that will be because the servo will help.

Are both of the rear calipers actually working? Maybe one is working and one siezed?

Northerner

23-04-2009, 20:50

The handbrake works well on both sides and the footbrake works but not well on either side.

One worth noting, when I sprayed the bias valve with gt85, the valve was squelching and blowing bubbles when I manually moved the valve lever, leaving me to think that there is a leak letting air in.

MAXIBOY

23-04-2009, 21:12

then i would assume the valves at fault..

as when started they work better with the servo means there working just seems not getting enough fluid.

could try bleeding them and see what fluid you have coming though..

no fluid poor valve..loads of fluid poor calipers..though i would assume valves as they are known for going..

Northerner

23-04-2009, 21:18

When I bled them earlier, the fluid appeared to be coming out ok, but that was using a pressure bleeding kit and not using the pedal.

I'm going to take the valve off the car tomorrow and see if I can repair it.

Northerner

27-04-2009, 11:03

Update:

The brake line connections are well and truly welded in the bias valve and are rounding off when pressure is applied so I decided to try and strip the valve down in-situ as much as possible.

The 2 internal valves were stuck and subsequently freed, brake fluid topped up and system bled.

What I have now is that the nsr brake works well on both the handbrake and footbrake. However, the osr works well on the handbrake but not very good on footbrake.

I'm starting to think the osr caliper may be the issue, but when bleeding the system after stripping the bias valve, the fluid pressure didn't seem to be good as before as the fluid was only trickling out when using the pressure bleeding kit.

MAXIBOY

27-04-2009, 12:29

then sounds like the bias valve is still at fault..

phantome46

27-04-2009, 18:41

is that the underneath of your car maxiboy?

MAXIBOY

27-04-2009, 19:29

is that the underneath of your car maxiboy?

yeah it is was still putting it back together then...

Northerner

28-04-2009, 21:47

Took the car in for its MOT and it failed on the parking brake efficiency.

The brake force meter readings were:

Footbrake- NSR 44kg/OSR 43kg
Handbrake - NSR 85kg/OSR 56kg

Park brake efficiency: 12% (16% is the pass mark)

I'm thinking this looking like a caliper issue after all.

What does everyone think?

MAXIBOY

28-04-2009, 22:41

did they pass first time..

yes if i remember..footbrake needs to work well enough to adjust them out so effects the handbrake..

if there not bleeding very well then the bias valve still looks at fault..

just change all three to be sure.. :lol:

Northerner

28-04-2009, 22:48

Damn!

Looks like I'll have to get the blowtorch out and see if I can get those hose unions out from the bias valve.

Any idea where I can get hold of a caliper refurb kit?

MAXIBOY

28-04-2009, 23:01

most motor factors and renault..maybe gsf..eurocarparts..

BristolSam16v

09-05-2009, 12:27

Better off just buying a new caliper, some guy was selling them on ebay for under 60 quid posted.

sleeky

12-05-2009, 16:11

Sorry to hijack this topic a bit but I was just about to post the same thing!

I have checked my bias valve and I can't move the 'pedal thing' freely, only a tiny little bit back and forth, doesn't feel as if the piston is moving.

I will try and bleed the calipers tomorrow but i suspect the valve is shot.

Lee.

busterhymes

12-05-2009, 16:54

worth just giving the arm a good sprayin with releasing spray may just be the arm pivot thats partially seized then leave it to soak then work it back and forth as you spray more on could do the trick good luck :wink:

Wobba

12-05-2009, 17:07

Undo the two little securing bolts at the end of the rod. Grease up the pedal pivot joints and push it back and forth loads. Push the piston in and test by letting the pedal go. It should push itself out by itself.

Once nice and free, put back together, get car on ground, get back under it and adjust the rod/nuts so the pedal is under pressure and fully open from the rod pulling it toward the front of the car. Not too tight, not too soft.

Test car and braking paying attention to rear balance.

Adjust as desired

sleeky

12-05-2009, 18:38

Thanks for the tips both...

I have left it to soak overnight in WD40 - tried to undo the nuts but they were rusted solid, shall see if there is any movement tomorrow :lol:

Lee.

Wobba

12-05-2009, 21:39

Thanks for the tips both...

I have left it to soak overnight in WD40 - tried to undo the nuts but they were rusted solid, shall see if there is any movement tomorrow :lol:

Lee.

The little nut on the end should come off quite easily tbh. Give the area a scrub with a wire brush. Hold the bigger nut to counter as you unscrew the small one. Should be easy after that.

busterhymes

13-05-2009, 07:05

you really need a penetrating oil WD is not really suitable i tend to use duck oil or whatever is available and see how u go just be patient and a bit of heat always helps so get the blowtorch fired up :) :)

sleeky

14-05-2009, 19:59

Well just had a go at it, managed to loosen the big nut off but the little nut is jammed solid, it just moves the whole thread! All fun and games eh. Will have a proper look at the weekend though.

Out of interest does anyone know the cost of a new valve from renault?

Lee.

Northerner

14-05-2009, 20:11

Just over £100 but they are on back order from France.

I was unable to unhook the spring from the rear arm without loosing the nut at the front. As the brake pipe unions were siezed solid into the bias valve, I stripped the valve down insitu and used long nose pliers to work the 2 internal valves.

After renewing the osr caliper, changing the pads and brake fluid, the rear brakes pulled 177/191kg on the MOT handbrake test

Northerner

14-05-2009, 20:27

Doh! Unable should read able.

katbloke

14-05-2009, 22:44

did you take photos of this process? especially for those with brake issues :)

MAXIBOY

14-05-2009, 22:46

what stripping the bias valve..

very simple much like a brake wheel cylinder..

got a kit and rebuilt mine..

BristolSam16v

16-05-2009, 09:49

There's a guide on retro-renault for the brake bias valve cleaning but I can't post the link cause im at work!

Wobba

16-05-2009, 10:27

http://www.retro-renault.com/forums/mechanical/46-rear-brake-bias-valve.html

BristolSam16v

16-05-2009, 11:13

http://www.retro-renault.com/forums/mechanical/46-rear-brake-bias-valve.html

Thats the badger

sleeky

17-05-2009, 14:28

Well just spraying mine with WD40 and having a good poke around seems to have done the trick, just been for an 'enthusiastic' drive and they seem to be working a lot better!

Thanks all.

vkosho

18-05-2009, 18:52

My car failed its mot today on the same issue! (parking brake efficiency) as well as a corroded brake pipe. Had a good look underneath and i think the bias may be something to do with it.

Im going to replace the rear pads first though as well as the pipe and test it again because the pads looked really low. Bias valves are a pain in the arse!