Bleeding clutch

[DVH]

started to bleed the clutch to change the black fluid in there, kept it topped up as I went along. now there seems to be no resistance.

No sign of a leak. Have I forgotten something

suspect that I have managed to get air in

thought about tying lever back to see if air makes its way back to the master cylinder overnight, can anyone see a problem with that.......or back bleed it by pumping brake fluid into the system through the bleed nipple

thoughts anyone??

[Guest ratchethack]

DVH, first off, I'm afraid I've gotta take you to the woodshed for letting your clutch fluid go skanky! I do this for your own good, my son, and it hurts me more than it hurts you...

 

You should always do a complete bleed, replacing all the fluid with NEW, FRESH fluid - not the leftover semi-skanky stuff in that bottle in the corner of y'er shed, rather than topping it off!! This is true for brakes as well.

 

This has been covered before, but brake fluid is powerfully hygroscopic. This means that it takes water vapor into solution directly from the atmosphere. But not only this, over time, it actually takes it in right through the plastic of the reservoir and the lines! Water is anathema to any clutch or brake system! Other bad stuff happens if you don't regularly flush all the old fluid out. Pete describes the kind of stuff that grows in brake calipers as "oysters". All kinds of horrid crap will grow in there if you don't completely change it all out!!!

 

If your fluid was black in color, chances are that the seals have gone past starting to degrade from chemical attack. You may or may not be OK just bleeding the system properly. I'd give this a go first (can't hurt) and hope for the best. If you can't get any pressure after this, it's probably time for a master cylinder rebuild.

 

You can back bleed it as you've described, providing there isn't some kind of blockage. Failing this, I'd have the master cylinder apart for an inspection.

 

Good luck!

[jrt]

What part was black? The stuff in the reservoir or the stuff you pumped out of the line? Ratchet may be right in that you have a bad seal. Better to go ahead and fix it- the costs of neglect here are pretty high.

 

You could try tying back the lever to allow a bubble to migrate up. At the very worst, nothing happens and you are out one night of waiting. However- if it's a seal, no amount of waiting will help- it will never feel right.

 

Damn, this reminds me I need to change my fluids out too....Clutch and Brake that is...you guys get your minds out of the gutter. There's other threads for that.

[belfastguzzi]

you have a bad seal.  Better to go ahead and fix it-

80107[/snapback]

[helicopterjim R.I.P.]

80109[/snapback]

 

TX!!!! Get yer club! Quick!!!!!

[tomsp]

and since nobody mentioned this, I shall get speed bleeders (on clutch and all brakes)- it'll make the whole process simple..

[DVH]

ratchethack the bike is just a year old and the fluid in the reservoir had badly discoloured, I am begining to suspect the master cylinder.

After trying to bleed again this morning I noticed the master cyl was slow to fill from the reservoir when the lever was released after the bleed nipple was tightened.

all thr fluids in the brake lines are just slightly discoloured which I would expect for a year old fluid. they have been changed no problem.

 

going tstrip down the master cylinder this afternoon think there is a fault with the return valve or the seals as you say have packed up.

[Guest ratchethack]

DVH, I really didn't mean to scold you. Sorry, I meant no offense. If the bike's only a year old, you're probably right - under normal circumstances, theoretically, the master cylinder and return valve seals shouldn't have had time enough to start decomposing yet! But if the fluid had been allowed to become "black", this is an indication that for some reason oxidation from water and/or air in the system had been allowed to create a corrosive cocktail out of the fluid. This stuff now ain't much like brake fluid anymore!! It "chemically cooks" the seals, premature though this may have been in your case. The black color in the fluid is actually the seal material in solution. It's also an indication that oxidation is at work on the rest of the internals - equally damaging. Who knows what may have got into the reservoir before you took ownership to kick off the oxidation process??

 

Just being able to remove all doubt about what's "in there" is one reason I don't ever allow anyone else to work on my moto's, but that's just me. This way, I only have my own record keeping and memory (such as it is ) to rely on.

 

As a general rule, regardless of age of the fluid, you shouldn't EVER allow your clutch or brake fluids to get dark colored. At first sign of discoloration, a thorough bleed's called for!

 

As I think Jason inferred earlier, it's possible that the damage is confined to one end of the system, and that the other end is OK. Fortunately, the two "business ends" of the system are separated by a long line. Contamination of the fluid generally starts at one end and takes awhile to migrate to the other. If y'er lucky, the seals at the clutch cylinder end are still intact. It's my understanding that your model has a diagonal frame strut that runs behind the clutch cylinder, making it a bit of a chore to get out. Mine comes straight back and out for a relatively easy inspection.

 

Best of luck!

[DVH]

Ratchethack no offense taken, I was just arsed off that something straight forward went belly up.

Ended up stripping the hole lot out for a look see, slave cylinder is fine, but seeing as I was there stripped cleaned and resealed

Master cyclinder was gummed up and not allowing the piston to return correctly, that also been resealed, bleed the system off bike appears ok now

 

I have had this sort of problem before when someone filled the brake system on one of my bikes with silicone fluid, who knows

 

just the stripped thread on the bevel box to sort, I sometimes wonder what gorillas PDI these bikes before delivery, My last Guzzi had stripped threads on sump and bevel box.

 

Tea break over back to the spannering

Dave

[Guest ratchethack]

OUTSTANDING, DVH! Good on ye for achieving a satisfactory result!

 

I had a similar experience to yours on y'er previous Guzzi:

 

First item of attention when I took delivery was an oil change, which exposed a little problem within 27 seconds: The shop wot put the oil in had stripped out the sump drain plug and meticulously sealed up the remaining thread fragments (which promptly came out with the plug ) with sealant to make it look nice 'n tidy.

 

This presented me with a superb opportunity to locate a new thread tap and helicoil set, take the sump out for a good look-see at the big-ends, oil pump, etc. and re-seal the sump.