MOT failure

[jim_jiminy]

Hi Guys,

so my MR-S has failed the MOT due to the handbrake efficiency.

The garage where I took it tried to adjust it so that it would work but they spent an hour and gave up. They checked the pistons, checked the cables, said there were no clips.

The car had new handbrake cables put in and new calipers and discs in May 2018.

They said no matter what they do they cannot adjust the cable so that it gives effective handbrake.

Any ideas? 

[Bossworld]

They need to ensure the piston is wound back out for an interference fit. That and then follow one of the guides on here for setup routine

[jim_jiminy]

Thanks buddy. I don't know exactly what that means, but I'll tell them. Do yu have a link to the correct guide? Is it the one that talks about stripping the calipers?

[paulj]

This is the link https://www.mr2roc.org/forum/index.php?topic=9783.0

My handbrake goes from great to useless around about every 6 months and this adjustment always fixes it.  Never changed any cables etc although the previous owner changed one to get through an MOT (!).  It wasn't well adjusted when I got it so methinks they may have wasted their cash.

You can do the adjustment yourself with a screwdriver and a spanner all from the comfort of the drivers seat.

[normanh]

I do the same as Paul each 6 to 8 months

Norman

[Chilli Girl]

Yep and me! . It lasts about 4-6 months for me.

[Bossworld]

That guide is correct for the setup but it seems a well trodden path that you need to ensure it's setup correctly at the brake calliper first.

@jim_jiminy - you would usually wind the piston all the way in when fitting new pads (you've mentioned everything has been changed). However, the auto adjuster on these is on a thread and if you don't wind the piston back out, you run the risk that the auto adjustment mechanism doesn't engage even if you follow the routine in the other post.

I imagine Jase will be along later to say something similar but the movement of the handbrake arm on the calliper actualy translates very little to the movement of the piston. Therefore it's important the piston's position is practically putting the pads on the disk at rest, hence an 'interference fit'. Otherwise it just isn't going to put enough force to hold the car.

[Ardent]

That pretty much covers it.

Edit
In relation to the last paragraph above.

[shnazzle]

I still don't get the whole "wind back 180deg" thing.
Handbrake off, pull everything off, wind pistons in all the way, wind out so that the pins line up with the slots in the pads, refit, pump brakes, start engine, pump brakes, pull handbrake.
Sorted.

Cables do slacken over the years and you can adjust for that in the center console. But that's more to reduce the throw of the lever to compensate for the slack, not efficiency of the brake itself. It's a stop-gap for changing cables.

Personally I've never adjusted the lever. To me it's an ongoing indicator of how close I am getting to needing to replace my cables. I reckon another year or two and the cables will be so slack I'll either have to adjust at console, or do the proper thing and replace cables. If you have so much stretch in the cables that you need adjust the slack, you have to wonder whether putting them under more stress by reducing the slack is the correct way forward.

But I'm alone on that thought hahaha

[Carolyn]

I've been trying to stay out of this...

That didn't work, did it?

Seeing as taking the wheels of and dismounting the calipers is WORK:

I note that the brakes in question were worked on last May.  Unless the handbrake has been rubbish ever since, I'd do the 'pedal' dance first, to see if the piston comes out and sorts itself.  If it doesn't, THEN I'd dismount the calipers and wind the pistons.

Note: the pedal dance only works if there's no tension on the cables.

[Ardent]

We can do all of the above and each part has its place.

The question is why do the handbrakes slowly get worse over a period of time? With the subsequent hand brake lever slowly pointing north.

Simply. The adjuster nut seizes (rusts) on to the thread bolt. Brake pads wear. The slack is not taken up by the adjuster nut as it is seized.

If you are fully in tune with your 2. You will notice a slightly increasing pedal travel for the same reason.
The initial travel takes up the slack. (Gap between pad and disc) then begins to brake.

Getting to the adjuster to un seize is not so easy as this is buried in the piston.

[Ardent]

@shnazzle
You are not alone.

[Petrus]

My pedal is high, the handbrake ok, I would líke it a bit lower but no issue.

Looked at how to adjust it and can séé the cable end nuts trough the console slot. Looks like I can get there with a pipe wrench to get the lock nut loose and the tighten them both with a long nose socket.
As it seems everybody goes in the trouble of even undoing the seats, it must be for good reason which I am missing?!

[Carolyn]

Jimmy is concerned about getting through the MOT.  Probably for as little expense as possible. 

Least complex/expensive first eh?

[shnazzle]

Jimmy is concerned about getting through the MOT.  Probably for as little expense as possible. 

Least complex/expensive first eh?

Definitely your approach. Handbrake off, brakes x10, engine on, brakes x10. Handbrake on

[Petrus]

Jimmy is concerned about getting through the MOT.  Probably for as little expense as possible. 

Least complex/expensive first eh?

Definitely your approach. Handbrake off, brakes x10, engine on, brakes x10. Handbrake on

Then adjust through the slit and repeat above.

[Carolyn]

We do tend to get carried away, don't we?

Petrus:  I slacken and tighten via the slit in the console too.  BUT if you've never inspected whether the cables are pulling evenly, then removing the console is worthwhile.

Jim:  If doing the basic adjustment doesn't work, let us know? 

[Petrus]

BUT if you've never inspected whether the cables are pulling evenly, then removing the console is worthwhile.

Point taken.
My teenage son is gadget expert and I will ask him to take photos with the endoscope he has on his phone. Stuff like this is ideal to get him involved.

[Ardent]

@jim_jiminy

In your orig post. You say new calipers.
Def new new not refurb new?

Beginning to wonder how refurbed some calipers are. Seals and cosmetics? Vs proper full strip down.

I wonder, just because so many posts have refurb calipers and still have issues.

Are they starting with at least an interference fit. Pad touching disc?

[Carolyn]

@jim_jiminy

In your orig post. You say new calipers.
Def new new not refurb new?

Beginning to wonder how refurbed some calipers are. Seals and cosmetics? Vs proper full strip down.

I wonder, just because so many posts have refurb calipers and still have issues.

Are they starting with at least an interference fit. Pad touching disc?

Probably not - but as long as the windout mechanism is engaged, they SHOULD pump out to that position, given a slack cable.

[Ardent]

They will pump out.
But they don't stay out, if the adjuster nut is siezed to the threaded bolt.

Rather winding along the thread as it should. The whole lot moves.

Edit
in all my revious posts when i say adjuster nut. The correct term is sleeve nut. Sorry.

[Carolyn]

They will pump out.
But they don't stay out, if the adjuster nut is siezed to the threaded bolt.

Rather winding along the thread as it should. The whole lot moves.

True but hopefully not in this case.

[Bernie]

Owners often do not use the correct method as stated in the handbook in the first place

First apply the brakes using the foot pedal then engage the handbrake lever




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[Bossworld]

Owners often do not use the correct method as stated in the handbook in the first place

First apply the brakes using the foot pedal then engage the handbrake lever




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It seems you need a friendly MOT tester for that, though.

I appreciate the whole piston stuff has probably become apocryphal but to my knowledge:

1) The rear calliper is pretty much the same design across MR2 MK1, MK2, MK3.
2) Paul Woods has written extensively on the topic on IMOC (the threads will show a similar split as it's a contentious issue).
3) Refurb callipers from Brakes International come with a leaflet advising the piston should be an interference fit (and not to wind the piston in further before fitting).

With that said, Mum had the rear pads replaced on hers, which is still on the original Toyota cables. The handbrake lever in the cabin subsequently had to much travel and all I did was the pump the brakes/reset the nut at the console worked fine for hers.

As others have said, perhaps take the easy route first but if it doesn't work, at least you have the next step documented.

It still confuses me how the MR2 handbrake 'design' can be so poor, I have a BMW mini with the same setup (mechanical handbrake actuating the rear piston) and that locks the wheels no problem at all.

[shnazzle]

Owners often do not use the correct method as stated in the handbook in the first place

First apply the brakes using the foot pedal then engage the handbrake lever




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It's common sense as well. It's not a hydraulic system. It's just a simple cable and lever system.

You can't expect a cable and a lever to have the same effect as a footpedal through a hydraulic system. So it's more of a case of locking the brakes in place with the handbrake, once the brakes have been pushed.