Re: MOT Failure - Rear Brakes - Need Advice

Post by **jimiller** » Tue Jun 24, 2008 2:35 pm

Hi All,

My car just failed its MOT today, and the race is on to get it fixed within 10 days. The official comments are "Nearside rear brake recording little or no effort" and "nearside rear brake binding." The tester told me that when the car was on the brake machine, the nearside rear brake didn't come on at first. Once they pressed the pedal quite hard, it came on, but then wouldn't release. I suspect I'm going to have to replace the cylinder, and possibly even the return spring. However, I am very inexperienced, and any advice on how to test for the problem, and how to repair the problem would be much appreciated.

Thanks,
Jon

Post by **rayofleamington** » Tue Jun 24, 2008 6:15 pm

A new cylinder is not too expensive, but it's best to get a new brakepipe at the same time as there is a good chance the old one will be damaged on dismantling.

Procedure is relatively easy if you have a bit of experience or someone knowledgable nearby to assist:

Jack the car and make sure it is safely supported and remove rear wheel.
Handbrake cable connects to a lever behind the brake back plate. Remove the split pin that holds the handbrake link pin. Remove link pin and move the cable away.

Remove the countersunk screw that holds the drum on (if it is fitted). The drum will be tight as the brakes are now stuck on! A bit of hammer work may help free it up a bit... you'll need to rotate it to find the brake adjuster. The drum has an access hole via which you need to undo the manual adjuster. This is located on the bottom end of the wheel cylinder, so turn the drum until the hole is roughly in line with the bottom of the wheel cylinder and using a torch or decent light have a look for it through the hole - it has a slot and can be turned with a screwdriver.
Once the shoes are de-adjusted everything should be free and you can pull the drum off (maybe using a bit more hammer work but not always)
With the drum off you will see the brake shoes and inside of the drum - both should be looked at for wear and replaced with new if needed (and the other side to match!).
Lever the brake shoe away from the cylinder and remove the adjuster. Then lever the shoes and move away from the backplate so they come off their seats and release the springs.
Then they can be taken off completely.

Next disconnect brake pipe. Once the brake pipe is disconnected (cut off if required) you can unscrew the banjo from the back of the cylinder.

When that is all removed the cylinder can be slid on the back plate to the end of the slot and removed completely.

Re-assembly is a reverse of dissassembly, but more care is needed!

1) the cylinder does not bleed well so ideally should be filled with fluid before fitting.
2) the cylinder should slide on the backplate easily so cleaning and greasing may be required (using brake grease or a small amount of copper grease)
3) when refitting the shoes, the springs need to be in correct position so make a note (photo or sketch) of where they were before they came off!
4) when fitting the rear banjo, new copper washers should be used.
5) the bleed screw needs to be at the top - best to check that it is ok before bleeding and replace if it is rusty on the cone.
6) re-align the shoes so they fit neatly to the drum otherwise adjusting takes longer.
7) refit brake pipe and bleed brakes - getting a good pedal may take a few attempts. When you get some pedal (ie it stops before the floor) then adjust the brake shoes until the drum just still rotates by hand.

now you should have a reasonable pedal, so make a few hard stops forwards and backwards to fine tune the shoe alignment - then re-adjust the brakes if needed.
9) re-bleed after a small amount of driving if you are not happy with the brake pedal feel.
10) make sure the brake pipe is properly clipped to the axle (otherwise you will eventually get a broken pipe and complete brake failure!!)
11) re-fit handbrake cable after all adjusting and bleeding is done, making sure that it does not pull the lever (adjust cable if needed) until you pull the hand brake.

one thing I forgot - make sure you fit a new ruubber boot on the new cylinder otherwise it will fail again quite quickly.

If it all sounds too severe - it should take less tha an hour in experienced hands so pay someone to fit your new bits (but make sure you get all the bits needed)

Post by **jimiller** » Wed Jun 25, 2008 9:54 am

Thanks! Got everything dismantled last night, and now I'm just waiting for the parts. Definitely looks as though the cylinder was seized. Oddly, though, when I disconnected the farside brake pipe, fluid dripped out, but when I disconnected the nearside, there was no dripping. There are no visible signs of kinks or blockages. Curious. I did order (amongst many other things) a new pipe, though.

Jon

Post by **MoggyTech** » Wed Jun 25, 2008 2:25 pm

Sounds like one of the flexi hoses is breaking up, they can act like a one way valve when this happens. Hence no fluid drip when pipe disconnected. If one is breaking up, i would replace the pair, as the other is likely to follow suit PDQ

Post by **alex_holden** » Wed Jun 25, 2008 2:34 pm

MoggyTech wrote:Sounds like one of the flexi hoses is breaking up, they can act like a one way valve when this happens. Hence no fluid drip when pipe disconnected. If one is breaking up, i would replace the pair, as the other is likely to follow suit PDQ

There is only one flexihose on the rear.

Post by **Dean** » Wed Jun 25, 2008 3:30 pm

Some great advice on here, the rear brakes is my next job!!!

Post by **MoggyTech** » Wed Jun 25, 2008 4:55 pm

alex_holden wrote:
MoggyTech wrote:Sounds like one of the flexi hoses is breaking up, they can act like a one way valve when this happens. Hence no fluid drip when pipe disconnected. If one is breaking up, i would replace the pair, as the other is likely to follow suit PDQ
There is only one flexihose on the rear.

Yes my Bad

Was thinking front brakes.

Post by **Dean** » Wed Jun 25, 2008 6:50 pm

Lets hope jimiller hasn't been looking and is still looking for the elusive second rear flexi-hose since his last post.

Post by **jimiller** » Wed Jun 25, 2008 9:55 pm

This is a big help, thanks. Looks like I have another part to order. One more question, though: if the single flexi-pipe on the rear of the vehicle is breaking up, wouldn't it prevent fluid from travelling to both sides, instead of just the one side?

This little MOT failure is becoming a fun lesson in my Moggy's brakes. Better than learning to weld in 10 days, though, eh

Post by **rayofleamington** » Thu Jun 26, 2008 5:22 pm

One more question, though: if the single flexi-pipe on the rear of the vehicle is breaking up, wouldn't it prevent fluid from travelling to both sides, instead of just the one side?

One failure mode is that the rubber swells up. The flexi hose has an outer braiding so the swelling all happens internally, leading to a blocked pipe. If this happens, then it would have also affected the right hand brake performance on the MOT.

I'd expect that when you fit the new brake pipe to the T-piece and press the brake pedal, you get a big squirt of fluid out of the open end of the pipe - if not, then you have an additional problem (but I doubt it based on your original post)

Post by **Dean** » Thu Jun 26, 2008 10:13 pm

Stripped off my rear brakes this evening using your instructions Ray. Thank you.

Fortunately everything came off easily!

Post by **jimiller** » Fri Jun 27, 2008 10:51 pm

Fitted everything up and passed the MOT

Pretty straight-forward and fun.

Cheers,
Jon

Post by **Dean** » Fri Jun 27, 2008 11:03 pm

Well done.

Post by **Welung666** » Sat Jun 28, 2008 12:14 am

Well done Jon

Post by **rayofleamington** » Sat Jun 28, 2008 2:57 pm

Fitted everything up and passed the MOT Pretty straight-forward and fun.

Well done Jon on 2 counts. One for getting it sorted and the other for giving feedback - it helps to keep motivation up for the people who offer guidance

Post by **MattRuch** » Sat Jul 05, 2008 7:58 pm

Ray-

That was a brilliant explanation. Thanks for that. I've printed it out.

Post by **bmcecosse** » Sat Jul 05, 2008 9:32 pm

The flexi pipes are checked in the MOT before the car goes on the rollers - any 'swelling' or leaking is instant fail.