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MG MGF Technical - Seized Handbrake

Hi,
Of the 8 MOT failure notices, these 3 are should be simple to fix (I hope)
1. Nearside rear parking brake recording little or no effort.
2. Nearside rear(park lever on caliper) Mechanical brake component has restricted free movement.
3. Parking brake efficiency below requirenments.
All these seem to tell me the handbrake mechanism has seized at the NSR calliper. Can the calliper be freed or does it need replacing?

MGF 1997 VVC (with ABS)
Mike
M King

If you search the archives, you'll find a number of entries on this. Not had the pleasure of this problem myself, but some say that cleaning and lubrication can do the trick, whereas others suggest that this is only a temporary measure, and a replacement caliper is needed (due to corrosion)
Rob Bell

Thanks Rob,
I've searched in the archive but only found more or less what you have said. I've "Cleaned and lubricated" but it's still siezed, perhaps a new caliper required?

Don't suppose you have any ideas/tricks how to remove a seized Brake disc? I've managed to undo the 2 retaining bolts and hammered til I'm blue in the face, but it won't shift.

Mike
M King

I had to file a notch, make a hacksaw cut and attack it with a cold chisel until the disc cracked through to the centre. It came off easily then, but it was hard work. Probably a good idea to loosen and retighten the discs as part of the annual service. (Never done it myself, though, perhaps I should!)
Mike Cunningham

A new caliper might be on the cards Mike - or certainly a reconditioned one.

Good tip from Mike there on removing a stubborn brake disc! I've got a problem with one of the ones on the Shed at the moment. I was beginning to wonder whether I'd turned into "Walter the softie" and wasn't hitting the thing hard enough!

Probably try a bigger hammer, and failing that... I'll try Mike's cunning nut-splitter suggestion :o)
Rob Bell

My 98 VVC OS hand brake was not working too well, turned out to be the fork end on the hand brake cable that had seized onto the caliper lever,restricting movement,freed off greased now working fine,good cheap fix,worth a look.
Andy
AS Douglas

Regarding getting a rear disc off:

Raise the car nice and high on axle stands so you can swing a proper big hammer at the disk from the inside outwards - no point in using a weedy light hammer. Continuous hitting is going to wreck wheel bearings etc, it's best each hit has good weight and speed to free off the rust and warped metal bonding of disc to hub. Don't keep hitting the disk at the same place - thump it firmly once, turn 180 degrees hit again. Now turn just 90 degrees and hit again, 180 hit, 90 hit,180 hit etc etc until the beggar comes free. Did mine in 6 blows with a club hammer.

My Tips:
1. Prior to hitting, put one of the wheel nuts back on - to act as reference to 180/90 degree movements. This will stop disk flying off onto self should you succeed, although they don't fly off that easily once they start to free off.
2. You ought to wear eye protection from flying rust or worse still, shattered disc parts.
3. When removing the two disc retaining grub screws, use an impact driver and big hammer - don't mess about with inappropriate screwdrivers.
4. Upon re-assembly, apply copper grease where the disc meets the hub and onto those grub screws. Makes life so much easier next time the discs have to come off. Make wheel removal easier by applying a smear of copper grease to the centre of the disc where the alloy wheel mates.
J Lennon

I particularly like the wheel nut tip - it's so easy to forget where you are on the wheel turning sequence! :o)
Rob Bell

To avoid undue stress on the wheelbearings, hammering ought to be kept to a minimum. The disc gets locked in position by corrosion around the outer edge of the drive flange it sits on, effectively fusing the two components together. Use a small screwdriver or pointed tool to scrape around the back of the drive flange to remove as much corrosion from that area as possible, then soak it with generous quantities of penetrating fluid. Use the straw attachment that usually comes with the can, as that helps to get the spray focused into the critical area - randomly spraying the back of the drive flange or the walls of the disc will achieve little. Turn the disc a few degrees and repeat. Leave for an hour, and give it another dose. When that's had time to soak in, there's a good chance you'll only need a short burst of hammer-rotate-hammer-rotate to start some movement. As soon as you can see the disc beginning to move away from the flange squirt another liberal amount of fluid into the gap, i.e. into the retaining screw holes and down the side of the studs, then turn the disc a few times to help spread the fluid around. Leave it a few minutes to soak in, then the disc will tap rather than hammer off the rest of the way.

To stop that happening again, wire brush the edge of the drive flange back to shiny metal and either brush on a coat of rust preventative or coat it in copper grease, and do the same with the corresponding area of the disc. A wire brush and light smear of grease over the drive flange face will help too, but only a smear.

Make sure you check the condition of the wheelbearings in future routine maintenance; if they have suffered from their ordeal it will accelerate the wear on the inner bearing race and if not spotted before it becomes severe wear the race can chew into the drive flange and you won't just be fitting a new bearing...
bandit

Thanks for all the advice, but I'm still banging away.

Problem is I can't get a good swing with the hammer. The calipers (which are hanging from string at the mo) need to be removed to give me more room and also to be unsiezed/replaced. How can I remove the flexible break pipe fron the caliper? I think it's connection is called a Banjo bolt.

Mike
M King

Reference to needing a better swing with the hammer makes me doubt you're surrounded by empty cans of penetrating fluid... It's also known as dismantling fluid, and no self-respecting toolkit should be without it. Bear in mind that the force a hammer blow puts on the wheelbearing is not a force the bearing was designed to endure, and they are far from indestructible. The nearside rear is the most likely to fail, so definitely not the one to abuse too much.

Exercising the handbrake mechanism to clear the corrosion may well restore operation well enough for MOT standards. Remove the return spring, soak the area of the dust cover where the lever shaft goes into the caliper body with penetrating fluid, and then follow that with some 3in1 or engine oil. Work the lever to and fro, and you'll see the piston moving out. Stop before the rubber dust cover goes taut, wind the piston (clockwise) back in (a wind-back tool that can fit on a ratchet extension makes this so much easier, a few pounds very well spent), then work the lever arm again. Repeat until the action of the lever gets easier, then re-fit the spring and test - if you work the lever with a screwdriver and then suddenly release it, the spring should pull the lever back to its rest position with a definite audible 'click', indicating that resistance is back down to correct levels. If it doesn't click, repeat the lubrication & exercise of the lever. An hour or so of persistent toil may well save you the cost of new calipers, which makes it time well spent ;o)

Correct procedure when fitting new discs is to fit new pads too, which if yours are perhaps half worn would put the piston & handbrake mechanism back to a different position and that position may be less affected by the corrosion & resistance issues.

The banjo bolt is easier to undo if you re-attach the caliper to the carrier. Fluid will drain out when it's undone so have a container handy to catch the drips. And don't be tempted to put that fluid back into the reservoir, it's carrying dirt and moisture now so is no longer fit for purpose. The moment you undo the bolt air gets into the fluid so bleeding that out will be necessary otherwise you'll be failing on service brake performance too, so I'd avoid doing that unless fitting a new caliper becomes the only option.

If you have a good local motor accessory shop, enquire whether they hire out disc pullers - large two or three legged pullers that dealers/workshops use. That would save any stress on the bearing and potentially a good deal of time too.
bandit

For any force, there is an equal and opposite force. When you hit the disk, then the impact goes thru the bearing to the hub. Would you put a bearing on the bench and knock the living daylights out of it with a lump hammer ??? If you do not think so, then you need to take the hub off to put it under a press to remove the disc and also the bearings to replace them.
If you do not do it today, then soon you will need to take it all apart again to fit a new bearing.
A 3 legged 10 Ton Hydraulic puller is a good investment or cheap insurance.
If you do not have the experience or tools, then give the job to somebody who has. It is much cheaper (and safer).
Geoff F.
Geoff Farthing

Probably is time to admit defeat Mike - I think that unless the disc doesn't shift reasonably quickly with a hammer, then probably is time to employ another method.

I am interested in the idea of cracking the bell, which seems like a cunning alternative method of releasing a seized disc.

The hydraulic puller costs between £100-130 - but I wonder whether it would be possible to hire?
Rob Bell

This thread was discussed between 21/06/2010 and 28/06/2010

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