Bad Master Cylinder ?

[SmithSwede]

I’m trying to bleed a hydraulic clutch.  I’ve replaced the slave cylinder, and the hydraulic lines are pretty new.    Can’t really seem to get all the air out.  Will try again tomorrow. 

Beginning to wonder if the master cylinder is worn, and thus not vigorously pumping fluid down the lines.   Or somehow sucking air back in.

How do you diagnose a bad master cylinder or one in new of rebuilding?  I knew the slave cylinder was bad because it was obviously leaking fluid.   The master doesn’t have an obvious leak.

Thoughts?   Tips?

[troyhamilton]

You might try to bleed it with a mity vac set up.

[Chuck in Indiana]

Use a syringe, and push fluid up to the reservoir.

[pete roper]

I’m trying to bleed a hydraulic clutch.  I’ve replaced the slave cylinder, and the hydraulic lines are pretty new.    Can’t really seem to get all the air out.  Will try again tomorrow. 

Beginning to wonder if the master cylinder is worn, and thus not vigorously pumping fluid down the lines.   Or somehow sucking air back in.

How do you diagnose a bad master cylinder or one in new of rebuilding?  I knew the slave cylinder was bad because it was obviously leaking fluid.   The master doesn’t have an obvious leak.

Thoughts?   Tips?

Well. What bike we are talking about would be a good start.......

[Darren Williams]

Tie the lever in against the grip with a bungie cord or similar for a while, Does it bleed off or will it not compress the plates at all? If it's the bike I think you are working with, you can easily see the movement.

If it is just air in the slave area (I had that happen once) compressing the air and releasing it while moving the slave around can get the bubble loose and let it travel up the line to the master cylinder. If bleeding and no visible leaks, that is probably seals and master cylinder will need rebuilding. Usually, but no guaranties.

Good luck sorting it out.

[SmithSwede]

Sorry.  It’s a 1996 Ducati 900SS. 

I’ve got a big horse syringe I’ll try today. 

[John A]

Sorry.  It’s a 1996 Ducati 900SS. 

I’ve got a big horse syringe I’ll try today.

On a Ducati you should use a cattle syringe
Sorry, it's early.  The evening show should be better

[SmithSwede]

At least you didn’t recommend I use Duck tape. 

[Furbo]

If the MC is original - yes, it needs a rebuild or replacement. That simple.

Otherwise, get it off the bar and stick a broom handle thru it and get if BELOW the slave cylinder. Bleed it then, hope that helps.

[SmithSwede]

I found a new master cylinder for $89.  I'm going to replace it, and install an new line while I'm at it.   

[SmithSwede]

Just to close the loop on this.  I replaced the master cylinder, installed new Galfer lines, new banjo bolts and copper washers.   

Works perfectly now.   

[PJPR01]

Just to close the loop on this.  I replaced the master cylinder, installed new Galfer lines, new banjo bolts and copper washers.   

Works perfectly now.

This is the same one we looked at in Cedar Vale, right Prescott?  Sucking air in, did you tighten sufficiently the philips screws on top to get a good seal?  Found that on my Norge one screw had worked loose and was sucking in air and softening up the clutch once headed thru Santa Fe...a quick tighten and all was good again.

[Chuck in Indiana]

Thanks for posting the resolution..

[Cdn850T5NT]

Use a syringe, and push fluid up to the reservoir.

That reverse-bleed method is (I believe) oft-used with light aircraft, to good benefit.  I imagine a person would want to cover the paintwork and at least loosely put the m/c cover on to prevent a geiser of brake fluid from damaging the paint lest any cylinder stiction be encountered... That and use a turkey baster first...

On second thought, cylinder stiction is not a factor.  It is syringe stiction.

[SmithSwede]

Paul, yes, the red Ducati.   Works great now.  Of course, since I basically replaced everything in the hydraulic system with new parts, it had to work good!

By the way, a local body shop guy repaired and repainted the busted left fairing.   Good as new.   $300

I won’t be making that mistake again.   

[PJPR01]

Excellent!  That was a painful sound for all of us hearing the Ducati go to sleep On its side!

Did you get the farkle for the reverse rotation exposed clutch?

Make it down to Houston last weekend?