Hand Brake/Rear Caliper - again.

MRG · June 1, 2018, 10:46

I wanted to share my experience of rear brake caliper issues in case the MR2r collective have any further advice. Three things to note off the bat, 1) for context I'm a novice tinkerer and hoped to use this as a learning exercise, 2) no pictures, sorry and 3) although I've learned loads, this is not a success story so I apologies if you found this while looking for a guide on how to do this right.

Here are a couple of diagram links that may help ....
http://mr2oc.co.uk/jimi/Mk1rearcalipers/CaliperRemoval1.jpg
https://toyotaparts.checkeredflag.com/images/parts/toyotaOEM/fullsize/a1_471919A.jpg

My story, along, I'm sure, with many of yours starts with an MOT failure. Mine, due to the hand brake not holding the rear drivers side wheel. This was similar to the failure 12 months ago which resulted in me paying a competent mechanic to replace one of the cables although I'm not 100% which side. This time however with me wanting to get some experience I would rather tackle the job myself.

My first port of call was to remove the centre console and have a gander at what the hand brake cable was doing. On inspection it was clear that the passenger side had full movement but the driver's side had none.

Next was to look at the caliper itself. I unhooked the cable from hand brake leaver at the back of the right drivers side caliper and attempted to manually move the lever by hand. Nothing moved, completely seized. Ok, that's not right, I have 2 options; new caliper or refurb. As this was a learning exercise I opted for the later. I picked up a seals and new piston kit and a few days later, when the sun was shining, got to work.

Using various guides from here and elsewhere and as many YouTube videos I could find I managed to get everything apart. Sliders out, piston and gubbins out, handbrake lever and seals off. It was obvious on removing the handbrake lever and seal that it was gunked up. I set to cleaning up and re-assembling.

One thing I noticed about the refurb kit was that there was nothing "inside the piston" inside the piston that I removed there flat metal piece jammed under a lip in the piston with hole in the middle that seemed to hold the receptacle for what I've come to know as the adjusting bolt. None of the videos or guides explained what to do with this. Do I need to remove and transfer on the new piston? Although, neither of the images I've linked show the parts I'm poorly trying to describe. As the piston I removed looked completely fine, I opted to put that back in.

I also didn't get a new bearing with the kit and not wanting to damage it by attempting to remove it I cleaned it out the gunk in situ and added a little grease that came with the kit. I put everything back together with the new seals from the kit and the lever was now moving freely. I patted myself on the back and took the rebuilt caliper to the car to fit, looking forward to rewarding myself with a cold beer. At this point, I realised my eagerness I had forgot to put in the snap ring, circlip thing that holds the adjusting bolt spring retainer (I thought it seemed too easy). Disassemble, reassemble and we're good to go. Again.

This time when I fitted, after I'd thrown everything together the hand brake still wasn't working. I checked the lever and it was freely moving but I was worried so I took the caliper apart again and checked the movement of everything as I put it back together again but still the same result. I noticed that there were some instructions on priming with the foot brake before attaching the hand brake cable so I tried that. Nada. I also tried bleeding the fluid a little although I don't have reservoir to collect fluid so it was a bit messy.

I'm left at the minute in the situation where the foot brake works fine. The hand brake cable in the centre console now moves roughly the same if not more than the passenger side. I can see how much travel the hand brake cable moves the lever on the caliper. I can replicate that with my hand while the caliper is disconnected and watch the piston move but it just doesn't seem to create any resistance when connected up.

I have gained the experience of 4 disassembles and 4 re-assemblies of the caliper, and learned how to puncture the piston seal when attempting to re-use it for the 4th time. Unfortunately, I haven't yet gained a working hand brake. I intend to get a vacuum bleed pump but I don't hold out much hope for that. Any feedback welcome. Thanks for reading.

Carolyn · June 1, 2018, 12:00

Slacken off the handbrake cables. Disconnect the cable from the caliper you've worked on. Start the car and pump the brake pedal at least ten times. Re-connect the cable and adjust them up.

That SHOULD do the trick.

MRG · June 1, 2018, 12:25

Thanks.

I had tried this without first slackening off the cable but I'll do the full procedure later. Video here if anyone finds this while looking for help https://www.youtube.com/watch?v=dw8BbpRsSbo

Will this procedure address the "1mm between lever and stopper" suggestion I've read elsewhere?

Carolyn · June 1, 2018, 13:31

Just an additional thought:

When you wound the piston in, did you wind it out 1/2 turn? Often needed to engage the adjustment screw.

MRG · June 1, 2018, 17:09

The hand brake adjustment seems to have worked

but now the hand brake light seems to be permanently on

. I've tightened it to 5 clicks. Have I tightened it too far? Is there anything other than the switch at the base of the handbrake that this light works off?

MRG · June 1, 2018, 17:28

Brake fluid.

Ardent · June 1, 2018, 19:56

With Carolyn here.

AS you will have worked out, despite the size of the crank arm the range of motion, the pin that it moves has a very small range of motion.
When you have wound the pistons in, then winding out and locating the pins in the back of the pad, Are the pads now touching the disc?
Alot of the action can be lost just gettingthe pads to the disc.

I assume that while asembling things back together. The nut moves freely along the threaded bolt. (the inside the piston bits) These often seize.

One other thing. Did the mechanic replace the cable correctly? was the correct handed cable used?
As they or one follows bit of an S shape path, there is room for error here.

Edit
With regards to the handbrake light coming on, it will, as that is what you are doing, essentially driving with the handbrake on.

Edit 2
anything useful here?
https://www.mr2roc.org/forum/index.php?topic=33557.0

frogger · June 2, 2018, 00:38

Confused about what you have done to bleed the caliper... if you've had it all apart as you say, I assume you have HAD to bleed it properly? But original post just says "I also tried bleeding the fluid a little although I don't have reservoir to collect fluid so it was a bit messy." .

This whole job is unbelievably dependent on a very specific order of operations and correct bleeding.

First You must wind the same piston out so that the pads are close to the disc, but the notch in the piston still aligned with the pad.

Next you must bolt everything up tight and correctly bleed the caliper (handbrake slackened and off). You do not need any fancy kit for this - just 2 people and discipline.

Then you start the engine and pump the pedal a lot to make sure the piston is fully out up against everything.

Then you adjust the handbrake cable so that it starts to move the lever at the caliper as soon as you move it towards notch 1, but the lever is just retracted and against the pin when handbrake is off.

If you do any of this wrong, or skip it - you will have a poor handbrake.

MRG · June 2, 2018, 22:57

Thanks for the replies. The hand brake adjustment procedure solved it.

The dash light was coming on because during the bleeding i had lost some fluid and it required a top up.

To try and clear things up by messy, I meant I didn't have a tube to attach to the nipple to collect the brake fluid once the air had escaped and I only had the help of a 7 year old on the pedal. She did a great job tho and it's all sorted. Thanks to everyone who replied.

MRG · June 2, 2018, 23:03

This is also what I was trying to describe.

How would one dissasemble this?

Ardent · June 2, 2018, 23:34

is this where the special tool mentioned in the above link comes in?

same link here
https://www.mr2roc.org/forum/index.php?topic=33557.0

frogger · June 3, 2018, 00:32

I've cut the piston in half to remove them before, and fitted in to a new piston.

frogger · June 3, 2018, 00:40

Just reminded myself and the special service tool is for a handbrake component, not the piston. I can't see how you would remove without cutting.

I also found my post form 8 years ago when I cut some out!

https://www.mr2roc.org/forum/index.php?topic=31246.msg381450#msg381450

MRG · June 3, 2018, 07:41

I re-used the old piston as it was in near new condition anyway.

I'm very surprised the refurb kits come with a piston but without the internals. Especially when the ability to re-use depends on a very accurate cutting of the old piston.

WARNING: If you're replacing a rear brake piston you will be required to grind your existing one in half without damaging the internals.