Hydrolic Brakes

[charlesea]

I replaced the old master cylinder that was installed in 2010 that came from Summitt Racing with the same one.
All was going good until about 2 weeks ago & the wheels started locking up. Does anyone have any idea why this has happen?
I bled off one wheel & it was ok for a few days & the same thing happened agin.
The lines are steel complete going from front to back.
Thanks for any suggestions to correct this problem.
Charles Andrews 334/799-5442 or reply to the post.

[Harpkatt]

Have you ever bled the brakes out and changed the fluid? DOT brake fluid can crystallize and cause lockup,water intrusion will ruin fluid quickly. Has happened to me on a motorcycle before. Rust is another cause, Does it go away when you drive a bit? See if you can trace which wheel it is, if you can take another look at the master cyl.

[Keith True]

Sounds like you may have a rubber line collapsing in on itself.Fluid goes out under pressure,but won't return under the low pressure created by the brake springs pushing the wheel cylinders back in.Also,your new cylinder may have a residual valve in the end of it to keep the calipers from retracting when used with disc brakes.

[Robbie Horn]

Make sure you have some free play between the mastercylinder & brake pedal.

[Keith True]

I forgot about the freeplay.Where you just changed the master,the pushrod may be just a little off from the old master.If it's too tight you will always have a little residual pressure on the fluid because it can't all return with the plunger still pushed in just a tiny bit.This is something I used to see a lot of on old Volkswagens,the pre-68's anyway.

[bbrocksr]

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Originally Posted by Robbie Horn

Make sure you have some free play between the mastercylinder & brake pedal.

Like Robbie says free play between the pushrod and piston.

Bill