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Old 03-19-2015, 04:48 AM   #1
Zapp22 OP
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How to find leaks in rear Brake system?

hi gang I had posted earlier about a little rear brake issue but need now to get down to identifying, or assuring, which part/s to replace.

cut to the chase - on a 05 Weestrom i had to re-set the rear caliper [po missed it] in its tongue-groove restraint. Removed the brake line altogether, removed the caliper, wheel, reassembled, aligned the rear, set the slack, then put the brake line on, torqued everything to spec, filled reservoir, and began bleeding.

the bleeding never gets 'done'. pumped the pedal a hundred times or so, pump, hold, open, close. finally got a tiny bit of Dot 4 running spitting out the bleeder, but never really got pressure. What's stumping me is that I'm not seeing any obvious leaks.

is Dot 4 THAT heavy? How do I figure out for sure where the leak is? or is there something hindering the movement of the fluid into the master cyl? this bike only has 16k miles so the mc has not that much use and before the current, I never had a hint of trouble from it. The 'occam's razor' here is that the hose is bad, at the fittings. But with so little pressure, it ain't obvious.

question about the Master Cyl: its a 'one-way' hydraulic pump, right? so it should be opening a valve at the 'top' to let fluid in, shutting on stroke and opening the other valve to apply pressure to the line/system, right? is there a way to force fluid into the inlet valve, or at least ensure that its filling?
or am I way off base?
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Old 03-19-2015, 04:55 AM   #2
trailer Rails
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Are you having trouble bleeding the system? Sometimes air can leak around the bleeder fitting threads. Also when using the pedal/lever to bleed, use slow deliberate movements. Fast pumping and just letting the pedal snap back can introduce air. Some times it is better to use a syringe and rubber tubing to push the fluid in from the caliper and another syringe to suck fluid out of the MC.
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Old 03-19-2015, 05:09 AM   #3
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First off, DOT 4 isn't necessarily heavier than 3, just different chemical properties. Just use whatever the OM calls for.

What do you mean " hose is bad?" Normally if you're having trouble bleeding your brakes it's because of air. Once the system is bled, any leak will occur when you apply the brakes and you will see where the fluid is weeping. It's possible your sucking air at the " bad hose" while attempting to bleed the brakes? Usually when people have problems like this it's technique, or you could have a bad / dirty master cylinder, may need to reseal it. Were the brakes working fine before the caliper was reassembled incorrectly? Could the caliper have been damaged when it was installed wrong?
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Old 03-19-2015, 05:31 AM   #4
Zapp22 OP
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well, the last comment sort of gets at one question. you're talking about suctioning fluid OUT of the MC, which implies to me that there is not a "one way only" valve there. so, you suggest removing the reservoir and applying suction to the feeder, and let IN fluid at the caliper? did I get that right?
not to second-guess you too much, but it would seem to make sense to pull/evacuate from the caliper end, creating a vaccuum that the fluid will fill...

to technique: slow/delib one stroke only? i.e.. wrench on the bleeder, close bleeder, stroke 1 time, open bleeder, close bleeder, rebound pedal, stroke again, reopen the bleeder, etc wash/rinse/repeat?

thanks mucho
Quote:
Originally Posted by trailer Rails View Post
Are you having trouble bleeding the system? Sometimes air can leak around the bleeder fitting threads. Also when using the pedal/lever to bleed, use slow deliberate movements. Fast pumping and just letting the pedal snap back can introduce air. Some times it is better to use a syringe and rubber tubing to push the fluid in from the caliper and another syringe to suck fluid out of the MC.
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Old 03-19-2015, 06:23 AM   #5
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It is not a one way valve when the pedal is not depressed. It is open. Once the pedal begins to be pushed down, it closes off the port to the MC res and becomes a closed system.

Sometimes you can bleed the system by removing the caliper, pumping the brakes until the pistons are almost falling out, then push the pistons back.


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Old 03-19-2015, 07:36 AM   #6
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Likely the MC is air bound and is not actually pumping fluid. Putting suction on the caliper bleeder can help get the initial air past the master. Or you can introduce the fluid thru a syringe at the caliper bleeder and push fluid back to the MC (need a way to remove fluid as it fills MC).
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Old 03-19-2015, 07:45 AM   #7
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As a point of reference, I use DOT 4 brake fluid in my DOT 3 brakes system. The two are interchangeable when the bottle says DOT4/DOT3 compatible. Also, the brakes can be (with some patience) bled using the 'gravity' technique - which works with all brake systems.

While I don't think Sir Isaac Newton figured this out, it does use a concept he coined - gravity. Simply fill the brake fluid reservoir, place the reservoir cap back on loosely (without tightening so some air can still enter), and open the caliper bleed screw. A piece of tubing (I prefer clear) from the bleed screw into a container will stop brake fluid from getting everywhere and making a mess.

The 'trick' to this technique? Patience - which some have very little, and that makes this technique impossible. It will take ~ 30-45 minutes for the fluid from the reservoir to fill the caliper. At which point the reservoir needs to be refilled and another 30-45 minutes allowed for the fluid to slowly drip out. This is also a very simple way to change the brake fluid. Good luck!
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Old 03-19-2015, 09:47 AM   #8
Zapp22 OP
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that last answer makes sense to me ... that, of course, doesn't mean your answer is accurate!

in the interim here's what I did:
- put a vaccuum tube on the bleeder and sucked repeatedly, creating a decent "siphon" vac. got a bit of fluid out but not a lot. tried pedal/pressure bleed again. no results worth mentioning. no real tension on the caliper.
- removed the mc/cover, put the screws back in to hold it stable. removed the brake line at the MC. put my finger tightly over that opening and pumped the pedal. it took a few pumps but the MC filled with fluid and it spurted at what seemed adequate force "every which way" from my pressurized fingertip.
- re-attached the brake line at MC, removed the other end, put that end over my catch bucket. very little fluid in the line at all - literally a few drops.
Pinched the open end of the tube fitting tightly between my fingers and pumped the pedal. I would get pressure, and a vaccuum on rebound, but never enough to move fluid down the line in any volume. pressure would fade.

my conclusion is at the least the line should be replaced. occam is likely right this time.

anyone have experience with Procycle's stainless steel "uprgade" brake lines?
the stock oem part is really hideous - it must be a multi-bike part as it is WAY long for this bike and a really difficult fit.

also, I have another question: the channeled bolts that attach the fittings of the hose on both ends: are they directional, or is there enough space engineered in that the fluid forms a collar that finds its way to the channel, under pressure... ???
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Old 03-19-2015, 11:30 AM   #9
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Banjo bolts they are called.Bolts have a channel and so do the banjos. Nothing directional so you'll be fine.

Brake lines upgrade? Doesn't Suzuki have that in their maintenance schedule? 4 years and should be replaced.

As a side note, the DOT regulations require that all hydraulic lines sold for replacements on motor vehicles be date coded.May even include OEM lines on newer vehicles, I think the regulations have been amended not too many years ago. Little rubber ring around the lines with the manufacturing date.
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Old 03-19-2015, 01:24 PM   #10
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try reverse bleeding using a syringe-type tool to force brake fluid into the system from the caliper bleed fitting . . . . . .
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Old 03-20-2015, 01:15 AM   #11
nickguzzi
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http://www.gunson.co.uk/item.aspx?item=1818

This is the most failsafe tool for bleeding I found. It even bleeds the long front to rear pipe on a guzzi.
Only point of difficulty is to get a m/cyl cap which fits. I got a spare one which I adapted.

It works like the ones used on the production line when I was an apprentice.
The (low) air pressure from a tyre, perhaps, purges fresh clean fluid through the system.
Don't reuse fluid, its full of dissolved air.

It is easy to use on your own.
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Old 03-20-2015, 07:20 AM   #12
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Quote:
Originally Posted by nickguzzi View Post
http://www.gunson.co.uk/item.aspx?item=1818

This is the most failsafe tool for bleeding I found. It even bleeds the long front to rear pipe on a guzzi.
Only point of difficulty is to get a m/cyl cap which fits. I got a spare one which I adapted.

It works like the ones used on the production line when I was an apprentice.
The (low) air pressure from a tyre, perhaps, purges fresh clean fluid through the system.
Don't reuse fluid, its full of dissolved air.

It is easy to use on your own.
I make a similar brake bleeder when replacing all the rear ABS brake hydraulics on my truck (lines, hoses, wheel cylinders,etc). A steel plate was the replacement cap for the MC with a piece of bicycle inner tube glued on for the sealing surface. The schrader valve from the inner tube was inserted through a hole drilled in the steel plate. The plate with the tube was then clamped to the MC and low pressure air used to force brake fluid through the hydraulics. As mentioned, the trickiest part is getting a spare MC cap (or making one). It makes quick work of bleeding.
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Old 03-20-2015, 10:59 AM   #13
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When I was bleeding a new trailer brake installation, I could not get fluid to flow either by pumping the master cylinder or by drawing with my MightyVac. I finally got 20' of clear tubing and connected the brake bleeder to a vacuum port on my Camry engine and used that (including the separator cup from the MightyVac so I wouldn't pull brake fluid into the engine). I DID get fluid then, with lots and lots of froth in it from a massive fitting leak at the caliper. Once I retightened the fitting, all was well.
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Old 03-20-2015, 11:16 AM   #14
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^^^

That's been my experience using the MityVac as well. The problem is either: a) the bleed screw doesn't seal the air leak so all that is pulled is air (and that includes using new bleed screws with teflon tape); or b) the vacuum line to the bleed screw won't stay attached (which also will create a mess). I thought about trying 'speed bleeders' but have been reluctant to install them since an air leak will pull air back into the brakes. Some seem to find them good. As noted, the gravity drip method has been the most consistent and reliable method for me.
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Old 03-20-2015, 01:43 PM   #15
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Yup, using a low pressure to push the fluid saves all sorts of mess and hassle, which is why I recommended the eazibleed or as Stan mentions, it should be easy to fab up something similar.
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