Failed MOT - Offside Rear Parking Brake "Inoperative"

[Dagnet]

Hello, took the car in for the MOT today and found out it failed due to "Offside Rear Parking brake inoperative on one side (1.4.1 (a))".So I took the car home and had a look to see what's going on.

I lifted the rear offside wheel and rotated it with handbrake off, halfway and full. It rotates freely when off, some resistance when halfway and difficult to rotate when full. I did the same with the nearside rear that passed and there's definitely more resistance with handbrake applied. So the offside rear parking brake is kind of operative, but isn't working at full efficiency.

I took the wheel off to see how the handbrake cable connects to the brake caliper and watched it compress and extend as I pull and release the handbrake. It moves ok but not as full range of motion as the working brake. Rear brakes with pedal work fine on both sides.

Any ideas what I should do? Thanks.

[Joesson]

@Dagnet

My pet theory is to make sure that what you have got is in the correct operating mode before you start adjusting, taking things apart or buying new parts.
To do that make sure that the brake cylinder pistons are freely moving and extended fully by pumping the foot pedal with engine on. I would try that perhaps more than once and then work from there.

[Dagnet]

Hello, thanks for the reply, I'll check that out

[Gaz mr-s]

The handbrake is a bad design, & the most common cause of MOT failure. I'd guess the piston is moving since the footbrake is ok.   Back off the cable tension inside the car, disconnect the cables from caliper lever, get a hand from someone, & operate both caliper levers. Are both sides comparable?

Check the rubbers on the ends of the cables & the ability for the cables to move.

[Ardent]

@Dagnet

To add to the above. To remove the tunnel it is held in position by 4 screws. The 2 rear eady access. The front 2 (if not already removed) are obscured by the seats. Easiest is to unbolt the seat. Let back rest go full forward, which then allows to tip the seat back revealing the hidden screw. No need to remove the seat. That said. Not a biggie to remove the passenger seat. Gives better access. Remember to disconnect the cable 1st before lifting out.

Edit. Leaving the front 2 out makes no difference and easier next time. All 4 of mine are in the ashtray.

[Carolyn]

The piston is probably binding, giving less than the full range of movement. There are a few possibilities for this, however, including sticky cable, and stiff sliders.

As stated above, disconnecting the cable will help you to track it down.

Here is the link to the topic in our 'how to' section:

https://www.mr2roc.org/index.php?topic=68798.0

[Dagnet]

Thanks for the responses. I'm trying to disconnect the handbrake cable from the caliper and I'm running into all sorts of issues with seized components (see pictures). The holding pin is stuck. Have tried adding penetrating oil and hammering it out to no avail. And somehow the tunnel is fused with the holding bracket.





Any advice for me at this point?

EDIT: I've removed the tunnel from the holding bracket but the holding pin is still stuck.

[Ardent]

Thinking along the lines of.
A variation of the wiper arm puller. Or a socket large enough go ho over the head side of the pin and maybe a g cramp or something to act on the pin side. Locking pliers to rotate wiggle the pin.

Having removed the tunnel. Take it you have slackened off any tension.

[Carolyn]

Allow some time for the penetrating oil to work.  If you have it, a flat headed punch is the tool of choice for getting the pin out.

If you can apply heat without damaging the rubber on the cable, that too will help.

[Gaz mr-s]

It does look like there's still tension on the cable, the rubber looks compressed.

[Dagnet]

I finally managed to get the pin out using a ball joint removal tool.



I've removed the caliper and inspected how the piston moves when pressing the handbrake lever. The piston moves very little, maybe 1 or 2 mm. I inspected the handbrake cables and it appears to be rather compressed when there's no tension on it.



Is the problem likely to do with the caliper or the handbrake cable? Thanks.

[Joesson]

Slacken off the handbrake cable, from inside the car, and see what movement and how free the movement is  in the cable.

[Ardent]

@Dagnet

Despite the lever arm length, hidden out of sight is a small silver bullet/pin.
The arm acts on that pin to compress the pads against the disc. The pads need to be touching the disc to begin with. Interference fit. So the 2mm of movement sounds about right.

[Gaz mr-s]

Cable wise, with them disconnected see if you can push-pull.  The rubbers disintegrate & let in water/dirt.  If they move at all they can be freed with a very thin oil down from the inside, but it's a very slow process.
Search 'Venhill' for a recent thread about the rubbers.

[Carolyn]

It sounds to me that the piston is somewhat seized and the cable is stiff.  As recommended you can free the cable with light lube from the top, working it in and out as you go.  Replacing cables is a big job, as you have to lower the tank.  If you do decide to replace, OEM is highly recommended.  Some of the aftermarket ones just don't fit properly.

Rebuild kits for the calipers are available and inexpensive if you want to have a go yourself.  If not, decent aftermarket calipers are also plentiful and quite inexpensive.  If you go that route, I'd recommend doing both sides.

Get some good silicon based grease (such as 'Ceratec') to lubricate the sliders after you've cleaned them up.

There's loads of info on brakes in our 'how to' section.

[Ardent]

As above.

I looked at rebuilding refurbishing a set of calipers.

 By time I had factored in the tools I would need to buy to complete the project.
Was not cost effective for me.
I just bought pair in the end.

[Joesson]

@Dagnet
Here is a link to the How To do a "Full rear caliper strip down and repair. Hand brake issue".
It is very clear and comprehensive. But be aware that you will need some tools, that you may not have, that will cause the cost of the exercise to be increased somewhat above the cost of the replacement parts.
It is worth reading just to get an understanding of what is/ supposed to be happening when the handbrake is applied.

Quick on the draw @Ardent beat me to it!

[Dagnet]

Thanks for the replies. I've ordered a new rear-right caliper off Ebay, wasn't too expensive - hopefully it will fit fine. The rear-left caliper looks like it was replaced, while the rear-right looks original. What type/brand of lube would you recommend for the handbrake cable? I'm Hoping I won't need to change the whole cable lol

[Gaz mr-s]

The cables have a ptfe or similar liner & are not designed to be lubed, but a thin oil works. Undo the support forward of the caliper to get the cable-end down low to encourage flow.  Start with a wd40-type with a straw. Then 3in1 oil or similar. First time I did it was 2019, the cable needed gripped with pliers to move. I've lubed it again since, and it still works.

[Dagnet]

The cable seems to travel alright but there is a sort of grinding feeling. Hopefully lube will improve it. Do you lube from caliper side or from inside the car?

[Ardent]

Inside, as the high point.
Shallow but gravity is your friend here.

[Gaz mr-s]

The cable seems to travel alright but there is a sort of grinding feeling. Hopefully lube will improve it. Do you lube from caliper side or from inside the car?

Cable rubber intact?

[Dagnet]

The little rubber boot before it connects to the caliper is a bit disintegrated and the rest of the cable I can see looks intact.

[Gaz mr-s]

The little rubber boot before it connects to the caliper is a bit disintegrated and the rest of the cable I can see looks intact.

That's why your cable feels rough....much better than mine were though.  See 'Venhill' mentioned above.

[Dagnet]

Looks like the old caliper had a partially seized piston - the new one travels a lot more. Lubed the cables as well and it has passed the MOT. Got a spanner trapped between the dashboard and the windscreen in the process...