Poor rear brakes

[dollywobbler]

The handbrake on my Mav was appalling, so I set about adjusting up the rear brakes. I'm wishing I'd checked the operation of the foot brake before I began...

I've now got a much improved (though still not superb) handbrake, but the foot brake appears to be doing absolutely nothing at all. I can put it in gear with the axle raised and while the handbrake will stall it, the footbrake doesn't do anything at all. This might explain why the front brakes seem to lock up very easily on gravel...

As the pedal is very soft, my first thought was to bleed everything, though I note that the bleed nipple on top of the compensator valve is very badly corroded, so that's unlikely to play ball. The compensator itself seems to move.

I did wonder if it was because there was no load on the rear suspension that the brakes weren't working incidentally, but the rear axle was on stands and therefore carrying vehicle weight.

Followed the tech sheet advice on adjusting, so shoes were adjusted until I could just get the shoe on, then handbrake adjusted up inside the car. I think handbrake performance is likely to improve as I did use a lot of brake cleaner. It was a bit gunked up inside, though I could see no signs of leakage anywhere.

 

[davenclaire]

brakes brakes n more brakes

the the price of a couple of rear brake cylinders i would change them then bleed the rear brakes out completly then have some one put pressure on the brake peddle while you turn the wheels making sure the brakes are working, lube all the hand brake cable points and adjust at the front not the rear, hopefully your load sensor hasnt packed up.

good luck

 

[dollywobbler]

I fear it might be the load sensor. Just tried bleeding the rears and nothing is coming out, which suggests no pressure making it to the back axle at all. I had another look at the load sensor. The arm moves, but the bolt I think it should act upon is absolutely seized into place. Not sure whether to try and force it (I have sprayed a bit of silicon lube around it) but I think this is the likely culprit.

 

[supergnome]

Have you checked all the vacuum pipes for leaks?

 

[dollywobbler]

I haven't, but the front brakes are working fine. If there was a vacuum problem, I'd expect a firm pedal and very little stopping power.

 

[supergnome]

You said "the foot brake appears to be doing absolutely nothing at all " in the first post so I thought of the vacuum pipes. David.

 

[dollywobbler]

Ah, sorry. Wasn't clear!

 

[makeitfit]

My vote goes to the brake compensator It too has a bleed nipple on it if you get it to move again. If it's goosed I could get one to you next week some time :sly

 

[iain.s]

may be being A bit stupid but how have you jacked it to test the brakes ? if the load sensor is sensing no weight why would it work as far as its concerned it would be dangerous to hit the brakes

 

[dollywobbler]

It was jacked on the axle, which means the weight was still in place effectively. That thought very much went through my mind!

Makeitfit, that'd be appreciated. Ta. I have a pal with a soon-to-be-scrapped Terrano lwb (handy for some new wheelnuts earlier today) but it's been sitting around for a good ol' while (interior is mouldy!) so I'm not sure the valve would be in a fit state.

 

[solarman216]

may be being A bit stupid but how have you jacked it to test the brakes ? if the load sensor is sensing no weight why would it work as far as its concerned it would be dangerous to hit the brakes

Load sensors do not work like that, with no load on the rear axle the sensor defaults to a minimum pressure set by the manufacturer so the rear brakes will still work fine, as load is added the pressure is increased proportionate with the load, my guess is the master cylinder is not drawing fluid, this is a common problem on dual cylinders, to get round it get an old master cyl cap and fit a pipe to it then with a syringe full of fluid apply pressure with the bleed screws open, another alternative is pump fluid into the rear bleed nipples and push the air back to the master cyl, Rick

 

[dollywobbler]

That sounds a possibility as the pedal is very soft. I might invest in an eazi-bleed kit, which does what you suggest and makes bleeding a lot easier generally.

 

[spiderpig37]

the eezi bleed kit i got didnt have a cap that fitted the terrano so got an old cap from scrap yard and drilled the top and attached a pipe to it works a treat:thumb2
cheers Andy

 

[dollywobbler]

Hmmm. Just noticed that the cap on my Mav already has a hole in it, I guess for that very reason. Seems a bit silly. A new cap is in order then.

Just wondering, largely because it's exceedingly cold and trying to snow (and therefore I'm not working on the car right now!) whether it might just be a master cylinder fault? Am I right in thinking that the circuit split on these is just front/rear rather than diagonal?

 

[dollywobbler]

Cured! Turns out there was a really bad air blockage at the rear. I used a stick to put pressure on the brake pedal, then left it a while. I then released the right-rear bleed nipple and it spat air and fluid out. Got my wife on pedal duty and bled as normal. No air in the LH rear, but the RH rear had an awful lot of air in the system. Three good pumps seemed to push it all out. Almost frostbitten, but I have working rear brakes!

The car is very slightly pulling to the left, so I fear my work isn't yet done. A lot better than it was with a nice firm pedal though!

 

[davenclaire]

well done

pulling left was a siezed front caliper brake slider on mine

 

[Terranical]

pulling left was a siezed front caliper brake slider on mine

Mine also pulls slightly to the left, was it the left caliper that was seized on yours?

 

[Terranical]

Mine also pulls slightly to the left, was it the left caliper that was seized on yours?

The reason I ask is, if the right caliper is seized it may be slow to actuate, meaning the left one comes on slightly sooner, causing a pull to the left.

 

[dollywobbler]

I think that's what I've got. The right-hand one seems to bind occasionally (gets warmer than the LH one) but it's definitely pulling to the left. To be honest, I don't mind any of this with my new motor. I'm getting to know it very well! Rear brakes have plenty of life in them and now work, fronts are low on pad depth, which may be exaggerating any caliper issues.

 

[11redrex]

Caliper strip and rebuild is not complicated but it can be a pig if they're badly corroded already. Uless you have the tools, somewhere clean to work, and a lot of patience, my advice would be to buy calipers already serviced, if you can find any.