Bleeding back brake

[Jools]

The rear brake line guide on my ST had somehow bent at a right angle to where it should be and rubbed a gouge into the rear brake line. Now I never use the rear brake apart from the occasional hill start, but even so I thought I'd better replace it with a Goodridge hose as part of a general fettle this week. But do you think I can bleed the thing :(

Now I've bled brakes many times before and here is what I'm doing.

1. Filled the reservoir with fresh fluid
2. Fitted a clear tube over the bleed nipple - with the end in a jar of fluid
3. Pressed the lever down slowly 3 - 4 times - hold it down on the last stroke
4. Open the bleed nipple 1/4 turn
5. Close the bleed nipple
6. Repeat the above until the lever firms up and no bubbles appear in the used fluid jar.

I can't even get the fluid through the system, and the reservoir level ain't moving.

Because I've obviously opened the whole circuit up to the air I even went to the extreme of detaching the line at the master cylinder end, opening up the bleed nipple, holding the line almost vertical and carefully pouring fluid straight down the tube until fluid started to weep from the bleed nipple. Then I closed the nipple, gave the brake caliper a few taps, flicked the line a few times and kept topping up the bare line over a period of about 5 mins until it wouldn't take any more and all the bubbles had stopped coming to the surface. I hoped that this would partially 'prime' the system. Lost a few drops putting the line back on but I'm still back to no fluid getting through at all

Any ideas from the more mecanically ept...assuming that ept is the opposite of inept.

[Queen_gravelpants]

Is your caliper fitted underneath the disc?

I had the same problem on my bike recently and thought my master cylinder had packed up, I asked my dealer and they said I had to take off the caliper and sit it on top of the brake disc whilst bleeding it....I did this and it worked!

[rockhopper]

I've always done it like you Jools apart from:

1. Open nipple
2.press lever down and hold down
3. tighten nipple
4. release lever

repeat as required.

Always works for me.

Paul.

[fatduke11111]

I had a prob with the rear master cylinder on my ST, It was cured by blowing out (into) the master cylinder as crap had got into it.

It wasn't exactly the same prob as yours as it caused the rear pads to not release (fluid wasn't being released back into the reservoir).

The guys at On yer Bike sorted it for me.

[Monty]

You mean to tell me that ST's are fitted with a back brake? why didn't someone tell me??:lol::lol::lol:

John

[Jools]

Well, it's done. In the end, I had to resort to mechanical aids (oooooooer missus).

A Gunson Eezibleed. It cost £12 summat and is basically a stout polythene bottle with a screwtop that has two tubes attached. One goes to the bottom of the bottle with the other end being screwed into a cap that goes on your master cylinder. The other tube just goes into the cap and has an attachment that you fit on the valve on a 'spare tyre'. As it happened, none of the master cylinder caps they supplied would fit so i had to drill a 10mm hole in the existing brembo cap and make sure that it gave me a pressure tight seal when screwed on to the reservoir.

Then you test it for airtightness, they recomend that you don't use any more than 20 psi, so I let my front tyre down a bit then clipped the thing onto my tyre. I had a bit of a leak but soon sorted that out. Once you have tested it for leaks you fill the bottle with fluid and connect up to the tyre again. This time the air pressure forces brake fluid under pressure through the system. All you have to do is use the bleed nipple as a tap, turn it on to start and turn it off when no air bubles appear in the fluid that's been flushed through. Easy Peasy - all the airlocks dealt with in seconds. You have to make damn sure there are no leaks though cos a geyser of brake fluid at 20 psi spraying at random from somewhere is not a pretty thought.

PS: Monty, I know...I never use it and it doesn't work very well anyway but an accident investigator might like the warm glow that comes from having a token back brake if I had a prang

[Edited on 9-9-2003 by Jools]

[itacud]

I've just had the very problem.
ie: master cylinder seems to be knackered.
What I did was filled a bottle of dot 4.
Removed the brake line from the caliper and put it into the bottle and held it above (2in) the master cyclinder.
I then pumped the master cyclinder a few time checking the oil level did not go below the min mark.
You should see air bubbles coming from the hose.
I then quickly attached the pipe to the caliper and used a brake bleeding kit from halfords.
Worked for me.
How much have people paid for brake calipers. I've been charge £80 for a ST4 rear with pads.....!

[electricsheep]

Originally posted by rockhopper
I've always done it like you Jools apart from:

1. Open nipple
2.press lever down and hold down
3. tighten nipple
4. release lever

repeat as required.

Always works for me.

Paul.

This is the method that use, but I found that an additional step helps.

Steps 1 to 4 as above, then pause for a couple of seconds before repeating, this allows time for the master cylinder to refil from the reservior.

pls excuse any spelling mistakes

Rob

[wayned]

Believing as you all do that duke back brakes are for show I was astonished to see at the MOT that mine now outperforms the front two (the performance of which has not changed) .. locking up the back is now a definite possibility.

Following an accident I replaced the master cylinder and fitted braided lines .. nowt else.

Dunno what the hells has gone on .. but I'm not complaining as is operates perfectly well .. releasing and such.

[rockhopper]

Locking up the back wheel is easy enough because there is no weight on it. A locked wheel contributes very little to braking effort though, thats why ABS is so popular. Feel is more important.

[Dave G]

I tried this on my 916 last year,the same method as rockhopper and it was just the most frustrating thing I think I've ever done,it really dented my confidence in doing those little(so called) simple jobs that almost anyone should be capable of.Perhaps those brake bleeding devices are the way to go,or in my case a mate to help.
I think the real problem is you just dont have enough hands to do it properly.
Strangely enough I replaced the front lines and bled them on the ss in less than half an hour.

[Glyn]

not taking the mick here but how can you have a problem with this. ido mine quite often and have never had a prob.
slacken that brake nipple off, pump brake, keeep resovoir topped up and retighten nipple jobs a good un.

[Jools]

I don't normally have a problem just bleeding the system when it's just a bit soft at the pedal (even though I hardly ever touch the back brake). Just when you change the line, all the fluid disappears from the caliper as well (well mine did) and you get air locks everywhere that stop the fluid pumping through sometimes. Once you've got the fluid pumping it's easy peasy

[Fordie]

Jools I reckon I must be Ya Man on back brakes having replace mine twice in a month. Bleeding I found to be a pain until.
First prime /bleed the master cylinder by releasing the actual brake hose, take it of completely. pump the lever with you finger over the hose hole feeling the pressure build up as the air is forcedout.Tighten up the hose to the cylinder once its primed. Next thing is to clear the air from the hose itself. Slowly slowly catch a monkey pump down on the lever to push out the air in the hose ,hose should now be free at the caliper end. Top up the fluid ressy as reguired, once the fluid comes out the end of the hose thats then full. The caliper I found a pain as well as its at the lowest level ,so I took of the caliper and raised it, cause air rises as we all learnt at school. Having raised the caliper it was easy to bleed it in the usual way. Pump, bleed, close valve etc: So now my brakes are as good as before apart from changing the Disc when it arrives from Ducati Coventry. Sounds a bit long winded but it works for me (Which an't saying much) 4D

[moto748]

I've been told that what you want is one of thsoe Mityvac vacuum brake bleeding kits.
Like these:

http://www.premiertools.co.uk/cat543_1.htm


I am seriously tempted!