Ducati 600ss brake bleed getting nowhere

Hi,

I own a Ducati 600 supersports (money-pit), and have replaced the front
brake caliper as the old one had 3 out of 4 pistons seized. It's a hydraulic
system, master cylinder on the handlebars down to a 4-piston caliper (2
opposite 2) on the wheel. I've checked, double-checked that everything has
gone back OK, and I have spent nearly a day trying to bleed the air out
since the system was sealed, but am still left with no resistance in the
brake lever. I'm using a hose on the bleed valve, I am keeping the res
topped up with fluid (new DOT4), I drained the system before starting, and
am using a jam jar to catch the fluid and keeping the other end of the hose
immersed in this fluid.

I have tried leaving a rubber band holding the lever in while I do other
stuff, there are absolutely no leaks, and I am positive that no air is
entering. The fluid is returning to the reservoir, as it squirts out if I
try pumpimg the lever with the cover off, but I am getting pretty much
nowhere with the bleeding.

I started out getting some big bubbles, but all I get now is either good
fluid, or tiny bubbles like a fizzy drink out of the bleed valve. Am I
missing something, or should I just carry on and the air will eventually
escape? I've got a jam jar with about 3 quarters of a litre of new fluid
that's come out of the system via the bleed valve and hose, but still no
resistance on the lever.

Any help much appreciated before I have to re-mortgage the house for more
parts from Italy..... Thanks!

 

Buy a Mityvac and grease the nipple threads before bleeding.

 

mentalguy2004 wrote:

If desparation sets in, you could try it the other way round and use a
big syringe to pump brake fluid in from the caliper end.
Grease the nipple threads, to stop air being drawn in around them.

 

Air being drawn in - that could be the problem.
Is the OP closing the bleed nipple before releasing the brake lever?

 

Look for high spots in the system where air may collect.
You might want the caliper loose instead of mounted.
The master cylinder should be the highest point in the
system with a straight shot from the caliper up to it.

Teflon tape or grease around the nipple might a help. Moving
things around a little might also help dislodge any residual
bubbles.

When I replaced a caliper, I used a syringe to draw out
fluid. After it sat overnight, the last of the sponginess
had gone away.

 

Don't forget to close the bleed nipple before releasing the lever.
Check that all the unions are tight otherwise air might be getting
in - you did replace all the copper washers when you rebuilt it?

To be honest I always had problems bleeding brakes until
I followed the exact instructions in the Haynes book and
it worked a treat.

If all else fails I have a good master cylinder for it as I swapped
mine for a twin disk system so fitted a 916 m/c and then swapped
it again for a Brembo radial...

 

| mentalguy2004 wrote:
| >
| > Any help much appreciated before I have to re-mortgage the house for
more
| > parts from Italy..... Thanks!
|
| Don't forget to close the bleed nipple before releasing the lever.
| Check that all the unions are tight otherwise air might be getting
| in - you did replace all the copper washers when you rebuilt it?
|
| To be honest I always had problems bleeding brakes until
| I followed the exact instructions in the Haynes book and
| it worked a treat.
|
| If all else fails I have a good master cylinder for it as I swapped
| mine for a twin disk system so fitted a 916 m/c and then swapped
| it again for a Brembo radial...
|
| --

Yes, I've been closing the nipple, and I replaced the washers and made a
mark on the banjo bolt head so the hole inside the bolt lined up the same as
the old one. I have the Haynes manual and was following it word for word.. I
am pretty convinced it must be the MC. There isn't anything else between the
lever and the pads, and certainly no leaks from the hoses.

I'd be interested to know how much you want for the MC; I have emailed a few
breakers to see if they have one. I just spent 150 on the caliper, I really
can't stretch to a new one from Italy, my wife will kill me LOL.

 

|
| || mentalguy2004 wrote:
|| >
|| > Any help much appreciated before I have to re-mortgage the house for
| more
|| > parts from Italy..... Thanks!
||
|| Don't forget to close the bleed nipple before releasing the lever.
|| Check that all the unions are tight otherwise air might be getting
|| in - you did replace all the copper washers when you rebuilt it?
||
|| To be honest I always had problems bleeding brakes until
|| I followed the exact instructions in the Haynes book and
|| it worked a treat.
||
|| If all else fails I have a good master cylinder for it as I swapped
|| mine for a twin disk system so fitted a 916 m/c and then swapped
|| it again for a Brembo radial...
||
|| --
|
| Yes, I've been closing the nipple, and I replaced the washers and made a
| mark on the banjo bolt head so the hole inside the bolt lined up the same
as
| the old one. I have the Haynes manual and was following it word for word..
I
| am pretty convinced it must be the MC. There isn't anything else between
the
| lever and the pads, and certainly no leaks from the hoses.
|
| I'd be interested to know how much you want for the MC; I have emailed a
few
| breakers to see if they have one. I just spent 150 on the caliper, I
really
| can't stretch to a new one from Italy, my wife will kill me LOL.
|

Just out of interest, has anyone ever rebuilt/overhauled a Duke caliper or
Master Cylinder? And if so, where did you get the seals, etc. because Ducati
don't recommend repair and don't stock the parts.

 

Using the patented Mavis Beacon "Hunt&Peck" Technique, antonye

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Not strictly necessary. Hit them with a blowlamp to get them red hot,
then let them cool.

They're now annealed and nice and soft.

--
Wicked Uncle Nigel - Podium Placed Ducati Race Engineer

WS* GHPOTHUF#24 APOSTLE#14 DLC#1 COFF#20 BOTAFOT#150 HYPO#0(KoTL) IbW#41
SBS#39 OMF#6 Enfield 500 Curry House Racer "The Basmati Rice Burner",
Honda GL1000K2 (On its hols) Kawasaki ZN1300 Voyager "Oh, Oh, It's so big"
Suzuki TS250 "The Africa Single" Yamaha GTS1000

 

I did but it was a long time ago on my Darmah....the master cyl had some
pitting so i just gave it to the local 'Brake & Clutch' utfit who sent
it away to be re-sleeved with a stainless liner.....it came back ready
to bolt on. I re-kitted the calipers myself with genuine parts. But this
was 15 years ago.......

Go and see your local 'brake & Clutch' shop, they have lists of
suppliers for all sorts.

 

Bugger. Beat me to it.

There's a footnote, though - don't hang the washer from the pointy end
of a longnosed plier, 'cos when it turns red and soft, it also turns
bloody oval. See that T-shirt - that's mine, that is.

 

Using the patented Mavis Beacon "Hunt&Peck" Technique, Pip

<G>

YTC

--
Wicked Uncle Nigel - Podium Placed Ducati Race Engineer

WS* GHPOTHUF#24 APOSTLE#14 DLC#1 COFF#20 BOTAFOT#150 HYPO#0(KoTL) IbW#41
SBS#39 OMF#6 Enfield 500 Curry House Racer "The Basmati Rice Burner",
Honda GL1000K2 (On its hols) Kawasaki ZN1300 Voyager "Oh, Oh, It's so big"
Suzuki TS250 "The Africa Single" Yamaha GTS1000

 

Teflon tape works well on the bleeders as well.

 

mentalguy2004 () gurgled happily, sounding much like they
were saying :

Ummm...

You don't normally need to worry about the exact line-up of the banjo bolt
to union. The union has a nice big groove within it to let the
fluid/oil/whatever run around freely.

Perhaps, since the bolt's been "lined up" it's not actually quite as tight
as it could be, and there's a bit of air sneaking in that way?

<disclaimer - not a bloody clue with banjoes on bike brakes, but I've got
'em on oil coolers and on car brakes, and nobody's ever suggested
alignment's even vaguely important>

 

If you are not too sure what you are doing, it doesn't hurt to put
things back on the exact same way you took them off. It may not be
necessary in this instance, but it's a good practice to get into the
habit of.

 

Could be an air bubble trapped in the line that floats up quicker than
you can pump it down, but doesn't have a straight shot back to the MC.
I have heard of hanging the calipers higher than the MC so that bubbles
float up to them. An other possibility would be to remove the caliper
from the disc and put something thinner than the disc between the pads.
Pump the pistons out to fill the cylinders, then push the pads back in
to force fluid back up to the MC.

Bruce Richmond

 

2 suggestions:

Make sure the two little holes at the bottom of the master cylinder are
clear, poke a needle in or something.

Wgen there's significant air in the system, as when you replace a
component, the idea is to get the air to rise up into the master
cylinder. Position the handlebars so the master cylinder is at the
highest point. With the bleeder on the caliper CLOSED, squeeze the brake
lever gently, you should see bubbles rise out the recently cleared holes,
a bit every squeeze. Tap the lines every now and then to make the bubbles
rise and make yourself feel better.

 

Bike on the center stand, turn the wheel side to side a few times too.
Wheel pointed left ought to put the MC at it's highest point. Also
helps
to loosen the bar clamp slightly and rotate the MC and lever.

 

That's a good 'un. Happens a lot.

I'd be tapping the calipers, too. And the unions, joints etc. all the
way up. I'd be tying the lever back to the bar and leaving it
overnight, too - surprising how often that sorts these nasty bleeders
out.

 

Modern Brembo multi-potters: no, they don't and you can't. We've done
this before.

ISTR Bonwick reckoning that you could take the seals to a seal shop and
have them match them, but I also STR someone else (maybe again Bonwick)
saying that if you told them they were brakes, they wouldn't. Product
liability, lawyers, etc etc.