Binding brakes.

DavidRutherford · Post by **DavidRutherford** » Fri Jun 06, 2008 12:56 pm

This is an odd one. I've never experienced binding brakes on a BX before (or indeed any vehicle with discs all round)

Just recently ran out of brake pads on my DTR turbo, so I slung a new set in that have been kicking around for a while here. Immediately the NSF brake started binding. Now, I'm not surprised about that as the handbrake mechanism return was completely knackered anyway, and prevented the handbrake lever from releasing properly.

Changed the NSF caliper for a good one, and put it all back together. No problems. Or at least there weren't until I had to brake heavily last night. Front brakes binding again. Tried the handbrake and there was NO free play there at all. Effectively the handbrake was on all the time, even though I know the cables have (a bit of) free play and the levers are working properly.

After much investigation it would appear that the calipers are fine, and that the problem is the pads. If I use the brakes gently, then it all works fine. There's still very little travel in the handbrake, but they're not binding. If I brake hard (and compress the brake pads hard) BOTH front brakes then bind fairly badly. My theory is that the brake pads are compressing too much and the handbrake mechanism is adjusting up. When the hydraulic pressure is released, the piston cannot retract far enough (As the handbrake adjuster has taken up all the movement) and hence the brakes bind until that little bit of brake pad has worn away (which takes a few miles and creates a lovely smell of burning and smoke from the front wheels!)

Despite a fair bit of experience with Bendix combined hydraulic & mechanical brake calipers (as fitted to the BX, Xantia, and also to various Fiats) I've never heard of this before. Has anyone else?

jonathan_dyane · Post by **jonathan_dyane** » Fri Jun 06, 2008 2:06 pm

David,

I vaguely remember having had a similar problem on my old TZD.

Can't completely remember how I resolved it, but I *think* I took the handbrake component of the caliper to bits and found that part of the adjuster mechanism had worn making it too eager to adjust up.

Sorry I can't be more expansive...

Alternatively, could the pads be defective in terms of the location and size of the pegs, so causing the piston to revolve and adjust up under heavy braking?

mnde · Post by **mnde** » Fri Jun 06, 2008 2:13 pm

Erm, this is the car that you have recently driven through a flood up to its headlights n'est-ce-pas?

Could maybe be linked?

*runs and hides*

Mark.

DavidRutherford · Post by **DavidRutherford** » Sat Jun 07, 2008 11:19 am

That did occur to me, but the handbrake adjuster mechanism is internal to the brake caliper in the cup of the piston, immersed in LHM and completely sealed. Even the levers have a rubber boot on them.

I have had a look at the handbrake levers since, and it's all free-moving and just fine. I even had the pads back out again, wound the pistons back and refitted them, but still the same.

By only braking gently, I've now got some movement back in the handbrake system, so it could be soft pads, or as Jonathan mentioned, a mechanism that is too eager to adjust up. I get the feeling that as the pads wear it will become less and less of a problem.... we'll see.

jeremy · Post by **jeremy** » Sat Jun 07, 2008 1:28 pm

If the car's been immersed - I wonder if the pads swell or the structure alters when wet?

If I fall over an old one in my garage I'll put it in some water and see what happens.

DavidRutherford · Post by **DavidRutherford** » Sat Jun 07, 2008 3:28 pm

jeremy wrote:If the car's been immersed - I wonder if the pads swell or the structure alters when wet?

I can't imagine so. Otherwise most cars on the road would be having problems with their brakes. After all, drive through a puddle 1" deep and your brakes get wet. Not to mention what happens when you pressure wash a car, and all the ford-crossings there are around.

I think they're just rubbish pads.

jonathan_dyane · Post by **jonathan_dyane** » Sat Jun 07, 2008 3:38 pm

I forgot that the mechanism was within the caliper and immersed in the LHM; it clearly wasn't the BX I was thinking about with the worn adjusters

If the pads are 'soft' they must be soft in a squidgy sort of way for the adjusters to tighten them up, may it perhaps be possible to observe this occur by having an assistant apply the brakes hard while you observe the caliper?

Jaba · Post by **Jaba** » Sat Jun 07, 2008 9:58 pm

Why not try releasing the handbrake cables. Either by slipping out the nipple on the end of the cables or backing off the outer cable adjustments.

I suggest this because if the handbrake lever on the calliper is not allowed to move back (forward) to its resting position then this could screw up the auto adjusting mechanism.

If the callipers are sticking on the through bolt sleeves they will not release the pressure off the disks on one side. This is unlikely on both callipers.

Realistically though. If it is happening to both sides at the same time then it is some weird manifestation of a hydraulic problem. Try bleeding first and SWHN.

Post by **mat_fenwick** » Sat Jun 07, 2008 10:22 pm

My brakes are still fine after this.

Although if you've taken a BX up to the headlights that's not bad going! On high? I would perhaps be inclined to change the gearbox oil in case the breather has sucked up any water.

DavidRutherford · Post by **DavidRutherford** » Sat Jun 07, 2008 11:35 pm

Jaba wrote:Why not try releasing the handbrake cables. Either by slipping out the nipple on the end of the cables or backing off the outer cable adjustments. I suggest this because if the handbrake lever on the calliper is not allowed to move back (forward) to its resting position then this could screw up the auto adjusting mechanism.

Both levers return to their forward position and there's still a little bit of cable free play (as there should be). There was a problem with over-tight cables before, but that was sorted at the same time as I changed the duff caliper.

Jaba wrote:If it is happening to both sides at the same time then it is some weird manifestation of a hydraulic problem. Try bleeding first and SWHN.

Did that, and it made no difference. I don't believe there's any problems with the hydraulics. I can absolutely guarantee it's a problem with the handbrake mechanism, as when the brakes are binding, there is NO free movement in the handbrake lever (other than the tiny bit of cable free play). Also, when the brakes are binding you can open both caliper bleed nipples, and the brakes are still on a bit, which has to be mechanical.

DavidRutherford · Post by **DavidRutherford** » Sat Jun 07, 2008 11:59 pm

mat_fenwick wrote:My brakes are still fine after this.

Although if you've taken a BX up to the headlights that's not bad going! On high?

Yes, On high. 1200rpm in 1st, with a remarkable bow wave.

You don't get much of an idea how deep it is, but from experience of the road (it's the only road to my house) it was probably just under or about 2' deep.

Did get a teeny bit of water in the rear footwells, but other than that, no ill effects... and a wet-n-dry vac sorted the small leak. I had to go through 4 times in the end.

As a sidenote Matt, having seen your other videos on Youtube, Was that you driving the digger? I love driving those but never get the chance.

jonathan_dyane · Post by **jonathan_dyane** » Sun Jun 08, 2008 12:14 am

Ten out of ten for balls, I'd of been paranoid about the (IIRC fairly low) air intake sucking up the water!

I once took the Dyane through a flood of such severity that the water was flooding in over the door sills. Remarkably the ignition didn't get wet, but I did find my oil to be rather watery the next day...

Post by **mat_fenwick** » Sun Jun 08, 2008 12:18 am

That looks deep. And good fun! I've gone through similar floods in my BX (although not quite as deep) when we had heavy flooding in Gloucester a few years back. Very strangely, both rear suspension cylinders started leaking within a week afterwards, from the usual corrosion of the aluminium. I drilled a hole in the steel shrouds to hopefully allow mud/water to drain in future and not sit next to the cylinder.

Unfortunately that wasn't me on the digger, I was on the dumper truck. Dyfed (whose ZX is still going fine with your old engine!) was driving the digger. I'm not sure how much you remember of the area we were clearing from when you were up here, but it looks very different now...

DavidRutherford · Post by **DavidRutherford** » Sun Jun 08, 2008 12:42 am

jonathan_dyane wrote:Ten out of ten for balls, I'd of been paranoid about the (IIRC fairly low) air intake sucking up the water!

The TD air intake isn't too bad. It draws air from around the top of the bonnet slam panel, about as high as possible under the bonnet, and is shielded by the bonnet. I think the bow wave helps a lot too as although the water was up over the number plate, it was a fair bit lower around the car, as noted by the fact that the floorpans were some 9-12" lower than the water line, but didn't fill up instantly.

AndersDK · Post by **AndersDK** » Fri Jun 13, 2008 9:46 pm

I'm pretty sure you have got binding caliper sliding bushes.

Its worth noting here, that the handbrake ALWAYS feels tight when the brakes are applied, because you can not move the pads further by the handbrake lever.
I believe this is what you experiences and you are then foiled to think its a handbrake issue.

Remove calipers and put some TLC service into all bits.

IMPORTANT : the contact area between the bushes and the hub may be corroded thus tilting the bushings a wee bit. Its VERY important to rub down clean the hub contact area to make it absolutely level again - preferably using a large file which you keep level over both bushings contact area.