Firstly, sorry for my seemingly first post being a cry for help - I've actually been a member of the forum for many years, lurked often but posted rarely. A mixture of a new laptop, new email address and forgotten username/password means that I've had to re-register.
Onto my technical question, and yes it's handbrake related...
As part of sorting a non working handbrake, on the old caliper I wound in the piston to what I think is 'all the way in'. But, when I tried to wind the piston back out nothing happened, it just span round and round, no movement in an outwards direction.
To add to this mystery, I bought a *new caliper online and this one does exactly the same. I wound the piston in, and now it won't wind back out. It spins perfectly smoothly (anticlockwise of course!) but no outward travel.
Am I doing something wrong or is this correct?
Thanks
Duncan
*It says new, it looks new, but are these things all reconditioned?
Hello.
Out of curiosity
Which brand did you go for?
Why did you wind it in?
Did it need winding in?
I take it not fitted to car yet to see the piston pushes out.
The piston is ´self adjusting´.
I.e. wound out by the lever but not pulled back.
Tatááá; one direction only ;)
I am no expert on this but I think the winding out is so that the adjuster mechanism sits in the right place to engage with the piston.
You would have to read the advert where you bought them from to see if they are reconditioned or not. You can get brand new ones but they will be more expensive. All the reconditioned ones I have bought looked brand spanking new because if has been stripped back to bare metal, repainted and then built up with new parts.
Thanks for the replies. (EDIT, only just seen the last one!)
I had to wind the old caliper piston in order to fit the new pads (thicker than the old ones!), plus I understand that winding them 'all the way in' is necessary to ensure that you don't end up with excessive handbrake travel within the caliper mechanism.
Foolishly (maybe) I wound in the 'new' caliper piston just to see if it did the same as the old one and of course it did - which leads me to think that there is nothing wrong with the old one after all :)) The new caliper was a cheapy from ebay, which is why I question if it is genuinely new or just a recon. If it is a recon there is certainly no outward signs, it really does look new.
I've looked everywhere online to try and gain a full understanding of how the self adjusting mechanism works, looked at videos and some diagrams etc, but I can't find a full explanation anywhere. I have read (from many sources) that after winding in the piston it's necessary to wind it back out half a turn 'to re-engage the self adjusting mechanism'. I have done this but that half turn seems to do absolutely nothing. Just to be clear, I do understand why it's necessary to align the slots in the piston correctly ;)
EDIT for Topdownman: Ebay advert says NEW, but you can never really be sure I guess! When I wound the piston anticlockwise I was expecting it to wind back out - apparently not then!
The piston is pushed out by it's action on the screw inside. For it to work, the piston must not be able to rotate, which is why the nipple on the back of the pad must locate in a slot on the surface of the piston. That way the piston climbs along the screw as it is pumped hydraulically.
Fully slacken the cables until they are exerting no pull.
Start the car and pump the brake pedal twenty times, slowly and firmly.
Switch the car off and release the pedal.
After hand brake adjustment check the levers on the back of the calipers are return to their stops.
Supposedly the auto-adjuster doesn't work until 7 ratchet clicks, so you don't want the handbrake lever stopping before then.
The rubbers on the ends of the cables need to be intact, - if they're not, there is a fix.
@Gaz mr-s said:
The rubbers on the ends of the cables need to be intact, - if they're not, there is a fix.I believe this to be the "fix" above mentioned :
https://www.ebay.co.uk/itm/MG-TF-MGF-MG-Gear-Change-Cable-Rubber-JOINT-END-SEALING-GAITERS-NEW-PAIR/122066392968?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Yes, they are from another part of another vehicle but they have been referred to/ used by others on here with, I understand, with som success.
Not tried them myself as mine remain in good condition.
PS
I had a look at the link and do not recall the prices as being £20+, so I looked some more and found this company , referred to on the MGF forum!
https://www.venhill.co.uk/cables-and-components/fittings-amp-components/boots-dust-caps-amp-o-rings.html?p=2
If anyone was in need and cares to ask they may have something at a more reasonable price.
I bought some of those mgf gaiters, rubbish in my opinion barely fitted at all, couldnt see them keeping water out, went in the bin...
Joesson's Venhill link.....these might do the job, much cheaper the MGF's prviously used.
https://www.venhill.co.uk/cables-and-components/fittings-amp-components/boots-dust-caps-amp-o-rings/rubber-boot-domino-ven207.html
Quote from: 105e on November 18, 2023, 17:43I bought some of those mgf gaiters, rubbish in my opinion barely fitted at all, couldnt see them keeping water out, went in the bin...
My first set fitted in 2019. The cables are still on the car. Not the easiest thing to fit, but the cables were never designed to have anything retro-fitted.
Quote from: Gaz mr-s on November 18, 2023, 15:25Supposedly the auto-adjuster doesn't work until 7 ratchet clicks, so you don't want a lever stopping before then.
Can I ask where that suggestion came from?
Never come across that before and I believe to be untrue.
Somebody prominent in MR2's for years, said a Toyota-served Tech told him.
An Engineer I know, & ex-2 owner dismantled a caliper & says the design of the handbrake mechanism is poor. A shaft with a square on it goes through a plate with a coressponding hole in it. They're not exactly 'interference-fit' & they're made of different hardness metals. The plate wears, so as time goes on the mechanical actuation becomes less & less efficient.
Since I learned that, I wondered if that's where the '7 clicks' comes from....?
Quote from: Gaz mr-s on November 18, 2023, 18:58They're not exactly 'interference-fit' & they're made of different hardness metals. The plate wears, so as time goes on the mechanical actuation becomes less & less efficient.
That could well explain a lot.
@SuperSix This may or may not help you visualise what is going on internally.
https://www.mr2roc.org/forum/index.php?msg=786930
As I mentioned above this is the thread from the MGF Forum, nice to know we are not alone!
https://mgfregister.org/forum/viewtopic.php?f=8&t=26365
For those who are curious
(https://i.ibb.co/jDT5pby/IMG-2699.jpg) (https://ibb.co/jDT5pby)
Can just make out the sleeve nut still in the piston.
I went through this a few years ago I couldn't get the handbrake to hold. Gave up in the end. Local garage got me callipers fitted now all ok. They could get the ones I bought to work either.
Thanks everyone for your replies, all very helpful 8)
To update, I did free-off the original caliper and get it working reasonably well, but considering that I had already bought a new caliper I ended up fitting that to get the handbrake working at its best. It clearly did the trick becasue the car went through its MOT today ;D
In terms of my original question, I'm still not sure exactly how the whole self adjusting mechanism works. I've read Ardent's description several times (thanks Ardent) and I think I get the idea, BUT, I really need to get inside the piston to see what's in there. I've seen plenty of diagrams (and some youtube videos) showing the adjusting bolt/spring/spring plate/strut etc that's located inside the caliper body, but nothing showing what's inside the piston itself. I realise now that the answer lies within! Luckily, I now have a spare caliper to play about with ;)
Don't forget that you need this to play around.
(https://i.ibb.co/12jSZ2g/Nut.jpg) (https://ibb.co/12jSZ2g)
I think some 90 degree long nose circlip type pliers are also of use.