If you have a firm pedal when you press it once,but lose it if you press it several times, sounds like the master cylinder(even though new) may be bleeding down through the seal or somewhere else in the system such as a caliper seal or a tee or line.I've had this same thing happen on the small KTM master cylinders and hydraulic clutches that used mineral oil,but these had rebuild kits available that usually solved the problem. Think you said it right though,"Guess you get what you pay for"

 

Hi again everyone...

Let me run through the chronology of this nightmare-please bear with me...

- unit came into shop with a complaint of no brakes. Customer tried repairing on own; purchased a replacement master cylinder and installed himself. Unable to bleed brakes as he could not get fluid to the lines.

- I removed the newly installed MC; inspected and reinstalled. Followed traditional principles for braking system. Could not get fluid from WC bleeders or air for that matter.

- blew all lines clear with air to ensure nothing blocking lines. That done, reinstalled MC and primed to clear air blockages. Bled each WC using foot method of pumping. FINALLY got air and fluid from each one. Problem now that claipers were locking up in braking pressure position following activation of pedal a few times. Also had followup conversation with customer to find out as much as possible about what he did prior to bringing it to me. He said he "adjusted a turnbuckle" under the hood. Found out that this was the adjustment on the rod that actuates the MC from the pedal.

Backed off the adjustment made by customer--rational being that locking the adjustment rod in the position he left it in did not permit full return of the MC piston-theoretically locking the pressure against the WC pistons and therefore the brake pads to the rotors. Well, backing this off achieved the desired result--wheels freed up and fluid now seen returning to the MC, which was not seen before.

Now, pedal is back at floor and can't seem to get it to stiffen up unless continual pumping; then marginal braking at best. Tried repeated bleeding; get fluid from WC bleeders w/o air.

I have almost eight hours in this machine and really do not want to admit defeat. I'm at the point of changing out all lines and both front and rear tee blocks (if I can locate them). Fluid that I do get from WC bleeders is a little cloudy. Bleed screws are not what I call the best quality-they do not have a typical SAE close thread and I suspect they suck air into the bleeding process when cracked.

-Should I put teflon tape or pipe dope sparingly on the threads to assist in providing a "seal" around them as I bleed? I've done a fair amount of work on automotive braking systems and I can tell you I've never been challenged the way this has hammered me!! Chinese knock-offs...

Almost ready to suck it up and admit defeat...

Hope someone out there can offer a bit of advice...

Thanks to all...

Tom

 

You can try teflon tape on all the fittings,but if I was doing this job I'd make sure to advise the owner anything I did from now on would be just like tracing electrical shorts:by the hour!

 

have you tried just to let them gravity bleed? Usually when i have issues with brakes i just crack the bleeders let em drain for a bit on their own and seems to always cure the problem.