Technical Handbrake efficiency very low, maybe unbalanced

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Technical Handbrake efficiency very low, maybe unbalanced

Mytheroo

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hi all, My 1.6 3-door failed on handbrake efficiency, but was probably so low that balance couldn't actually be tested. It passed on rear footbrake.

I've replaced pads and disks, bled, done the correct re-install procedure a few times. Bedded in (they are EBC disks and pads so have the bedding in material on. Footbrake applies well, can't turn with breaker bar on wheel nut kind of thing, and balance between rears seems similar at a foot pedal pressure where wheels can be turned with breaker bar on wheel nut.

I've removed the rubber bits on the top caliper sliders. NSR is a bit stickier than OSR with regards to pads releasing on pedal release, but it rolls fine, and starts rolling on minimal slope etc, nothing I'd think of as binding.

Handbrake starts activating before first notch, but overall efficency is just low, I can't lock the rears even in the wet. Stopping from say 10mph with handbrake only takes e.g. 3-5 seconds.

I don't really know what goes on inside the caliper when the handbrake is applied, some kind of rotating cam that reduces the volume inside? And a ratchet kind of thing for the auto-adjuster?

When I activate the handbrake level on the caliper with a lever (screwdriver) both sides rotate about the same amount before jamming solid and locking the hub, but I don't know (yet) if using the in-car handbrake lever moves them the same amount.

The in-car handbrake lever is moderately stiff, but tightens to a point on last notch where I'm about at my limit of strength applying it. And at this point the efficiency still feels low (and doesn't lock the wheels etc)

My unknown is not really knowing what can go wrong internally in the caliper. I guess it might just be stretchy cables though?

Any help appreciated
 
Inside the caliper is pretty simple. The brake piston sits on a threaded shaft, hence why you have to screw it in and out. Note that the near side rear is reverse threaded.

When you pull the handbrake the lever the cable attaches to on the back of the caliper turns the threaded shaft, making the piston screw outwards.

The pistons have two notches in the surface of them; the brake pad should have at least one corresponding notch in the bottom of it. It's important to line these up correctly so that when the handbrake is applied the piston doesn't just spin with the threaded shaft - which would prevent it from screwing out.

I've had nothing but trouble with the rear calipers on my Abarth; don't know why just is what it is. I've had to replace both rear calipers twice now due to either seizing or leaking. I've now just replaced the drivers side rear again (third) as the handbrake mech had completely seized and wasn't applying any force to the wheel at all.
 
This type of caliper is pretty feeble. Works okay on something little but a heavier car needs more pressure to pass the MOT and the Stilo just about managed it when it was new, never mind years later.

I'd not mess about.. just fit refurbished calipers (about £50 each exchanged). They'll be good for a few more years then


Ralf S.
 
well, it passed the retest.
Getting 20% where a pass is 16% and average is 30%.
Percentage of what? I asked, and my MOT guy said percentage of the weight of the car.
I didn't ask if it was measured weight at time of test or handbook weight. If weight at time of test, I'd have been wise to empty all the tools (seats?!) out before taking it in.

Since my first post I watched a few vids of VW calipers, though are very similar to ours.

I think I read about hassle bleeding the anti-lock part (?) and decided I didn't want to take apart the caliper blind, but maybe thats just JTD or fronts only etc as there doesn't seem to be any active anti-lock part in the caliper, just the sensor on the hub.
 
I think I read about hassle bleeding the anti-lock part (?) and decided I didn't want to take apart the caliper blind, but maybe thats just JTD or fronts only etc as there doesn't seem to be any active anti-lock part in the caliper, just the sensor on the hub.

Glad it passed mate.

bleeding anti-locking parts relates to the ABS pump and module. If you get air in there you're in for a world of pain and misery. That said, if in changing a caliper you get air in there you're either a clot or something has gone very wrong!

When you swap or take out a caliper just use some of those little orange hose pinch pliers and before you remove the caliper, pinch the hose - that way no fluid leaking out.

You're then free to take the caliper off, rebuild as you see fit or replace it. Put your caliper back on a bleed as normal.

As long as you're bleeding the caliper up straight away once you've fitted you're applying positive pressure forcing fluid out it shouldn't allow any air to travel up the system.

Have done it dozens or times, if not more, and never had a problem.
 
Glad it passed mate.

bleeding anti-locking parts relates to the ABS pump and module. If you get air in there you're in for a world of pain and misery. That said, if in changing a caliper you get air in there you're either a clot or something has gone very wrong!

When you swap or take out a caliper just use some of those little orange hose pinch pliers and before you remove the caliper, pinch the hose - that way no fluid leaking out.

You're then free to take the caliper off, rebuild as you see fit or replace it. Put your caliper back on a bleed as normal.

As long as you're bleeding the caliper up straight away once you've fitted you're applying positive pressure forcing fluid out it shouldn't allow any air to travel up the system.

Have done it dozens or times, if not more, and never had a problem.

am re-reading this, as I have MOT this coming week, and expect to fail on handbrake :-D

So, the ABS thing is in the engine bay? or kinda halfway down the car or something?
I've ordered some brake hose clamps, better than mulgrips I guess.
I think if it fails on handbrake, I'll get the refurb calipers.
 
So, the ABS thing is in the engine bay? or kinda halfway down the car or something?

The combined ABS modulator and ECU is attached to the bulkhead next to the brake/clutch fluid reservoir.. If you have the later ABS 8, it will look different to the one in the picture below.

I'll get the refurb calipers.

You could try resetting the caliper pistons.

1) Loosen the handbrake cable adjusting nut as much as you can without it falling off. You'll need a 10mm, deep socket (Picture below if of the MW version, saloon versions may look slightly different).

2) With the engine running, pump the brake pedal as hard as you can about 20 times.

3) Re-adjust the handbrake cable nut so that the rear wheels lock with 4 or 5 clicks of the handbrake lever.
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I have no idea where I got the notion that the bit that caused trouble if you got air in it was part of the caliper. Glad it's not though, I can clamp and do whatever I need with the caliper without worry then.
I don't think a simple handbrake adjust will do it. Even on full power (but not fully up, i.e. lifted strongly) the clamping power seems very low. When I tested last year, it was engaging slightly at 1 click, fully on at 4 clicks, maybe 5 clicks was possible, but still was weak wrt slowing a rolling car etc.
 
The procedure above is not a "simple handbrake adjust", it resets the mechanical handbrake mechanism inside the caliper pistons. You would also have to do the procedure if you fitted new calipers with old brake pads.
.

Compared to many jobs, I'd describe the procedure as simple. I was not misunderstanding you, or denigrating the instructions etc, soz if it came across that way :)

And this is what I did last time, though I didn't re-tighten the handbrake for a few days after changing the pads and disks, to let them bed in well, then did the 20 pumps to make sure all that was reset in the way you describe.

Do you think any issues with the cables could cause low efficiency? I can't think of a reason, unless other symptoms were present (like binding, or one side way worse than the other etc)
 
Do you think any issues with the cables could cause low efficiency?

Only thing I can think of is, a few years ago I noticed a problem with the left cable on one of my MWs. The outer plastic covering had worn off where the cable was touching under the floor pan. That allowed water to get to the outer cable, which caused it to start rusting. The outer cable is a long coiled metal part, and the coils were bunching up where the rust was, so the outer cable was getting shorter. The yoke that both cables attach to behind the handbrake lever maintained balance, but I replace both cables anyway.
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One of my recent (18 months?) refurbished calipers just decided to seize up its handbrake pivot. Joy! :D

If I leave the handbrake on overnight when it's been raining the handbrake doesn't release properly on that side (the pads bind on the disc) - the symptom is a very floppy lever (apart from the car drives like the handbrake is on).

I've squirted the pivot with WD40 and a spot of white grease which helps the lever return to its "disengaged" position for a while. I've also attached a big cable tie to it. It's easier to find that, to yank the handbrake lever back with it, rather than rooting around under the car while the handbrake is off. I'm sure the bastard is going to run me over one day. :D

I have a new (refurbished again) caliper - just £35 this time - so that'll sort it.

I sometimes wonder what dramas we're all going to have when our cars all have those auto-hill-holder/electronic handbrakes (as seem to be becoming more and more common). Something to look forward to... :D

Ralf S.
 
so, it failed on handbrake :)

also inner CV gaitor.

I'm replacing the cables and seeing if the caliper will work ok after a clean up etc.

Regarding the inner CV joint gaitor....does it hold in gearbox oil or not? I think the seicento did, but I've had driveshafts out of other cars where it didn't
 
just to update, changing both handbrake cables has made a massive difference. Haven't fully adjusted yet (need to change a pad first) and the lever is topping out on 10 clicks and still its way better. The old cables weren't too bad, but were just not moving the levers on the calipers as far as the new cables are doing.
CV inner gaitor doesn't hold in gearbox oil. Took off bottom ball joint, tie rod and then pulled the inner free (didn't touch the hub nut). snap ring holds the tripod/tri-wheel joint in place. Take that off and new gaitor can be slid on.
 
Aye... you beat me to it. The inner CV spider just sits inside that cup full of grease. The cup's spindle (left hand side) or the long driveshaft (right hand side) is the part that enters the gearbox/keeps the oil in.

Once you have the spider out, have a feel inside the cup to see whether there are any indents being worn into the cup by the spider. It should be all smooth (not including the three ridges moulded into the cup).

The spider comes off fairly easily usually, once you have removed the circlip.. and if you're lucky it goes on fairly easily too. A new spider (should you ever need one) is a rather more feisty affair that needs some "persuasion" (whilst not pressing/striking the moving parts directly).

I used an old Imperial socket of approx 25mm on the 23mm inner ring and the socket did get damaged slightly, so there's probably a better way... next time I might get some emery onto the inner ring first, to increase the diameter slightly.. I dunno.

The spider also likes a particular type of liquid grease, conforming to NLGI 0 spec. Your average CV joint grease is NLGI 2 (quite a bit thicker). You can make NLGI 0 by mixing some gear oil into you NLGI 2... since NLGI 0 is like rocking horse poo.


Ralf S.
 
very interesting. Didn't consider differing CV greases. However, I'm gonna have to use what was included in the kit, unless my 30 yr old tub (if I can find it) is actually NLGI 0. No time for anything else.
I do have a slight gearbox oil leak, maybe from whatever the cup seals against. There's slight in/out movement to the cup, as well as a couple of mm of forward/reverse slop which I suppose is expected. I don't know if the cup gets tightened to an oil seal or whatever though....again probably no time to investigate this time around...need the MOT retest :)
The leak is like one drip a day kinda thing.
 
Your old grease is likely to be NLGI 2. The black stuff that came with the kit might be a tad thinner but it's most likely to be NLGI 2 too. I don't think it makes a huge difference though... the new spider will probably out-last the rest of the car now.

Each cup is a snap-fit into the diff' housing. You can lever them out with a pry bar and a quick sharp tap from behind. To get them back in is the opposite but you need to make sure the spindle is fully engaged, otherwise it will leak gear oil out quite obviously. The back of the cup should be almost touching the casing when it's properly in place, if you don't hear it actually click into position.

Some movement is okay. It's just the play between the cup spindle groove and the clip in the housing.

The metal ring the cup spindle fits into, with the stamped holes around the end cap, is all part of the oil seal (the outer case has the usual neoprene ring bonded inside it). They can be levered out and a new one tapped into place.. so they're *quite* simple to replace but buy a good quality replacement rather than an unknown brand, since it's an interference fit and any poor sizing makes it tricky to press a new one into the diff without distorting the seal's alloy casing.

I damaged one trying to fit it.. :eek: but luckily (I knew there was a high chance that it was going to end badly) I'd bought 2... so I decided to rub down the second one a little (the outer alloy casing) to make it easier to tap into place. No problems since..

A small dribble of oil isn't severe but check the trans' oil level occasionally. Mine used to leak a small amount too but not so much that I couldn't wipe it off the diff casing before it dripped onto the floor.

Seals is a nice job for the summer. You can take the driveshafts and cups off without having to disturb the CV covers and by now all your suspension and tie-rod nuts and bolts should be nicely oily from having been apart, so will be easy to dismantle.. :D


Ralf S.
 
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