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Brake Master Cyliner Leak
Posted: Mon Jan 02, 2012 1:50 pm
by magnum
Guys hoping you could help. My 61 CJ5 is leaking Brake fluid from the top of the master cylinder. I have already replaced the master cylinder, both of the rear brake cylinders, pads and bled the system Any ideas why it could be leaking from the cap? Thanks.
Posted: Mon Jan 02, 2012 9:55 pm
by wesk
Brake pedal free play is inadequate.
Posted: Tue Jan 03, 2012 8:03 am
by magnum
Wes,
Meaning there is a problem with the amount of return? I know that once I stepn the brakes, they work well but start to leak out of the top. Thanks for the help.
Posted: Tue Jan 03, 2012 10:10 am
by wesk
The three primary culprits in a situation where the master cylinder seems to overflow are:
1-Pedal free play missing which continually applies pressure to the master cylinder.
2-Heat shield missing and fluid is expanding from the heat.
3-Check valve stuck inside the master cylinder.
You said you replaced the master cylinder so I ruled out #3.
Posted: Wed Jan 04, 2012 7:32 am
by magnum
I know that the heat shield is missing but since it was cold I never thought of that. I will check the return out today. Thanks again for the help.
Posted: Wed Jan 04, 2012 1:09 pm
by wesk
The difference in master cylinder fluid temp with engine not operating and engine operating is much greater in cold weather resulting in a greater amount of fluid expansion.
Posted: Wed Jan 04, 2012 7:24 pm
by magnum
Thanks Wes.
Posted: Tue Jan 10, 2012 4:44 am
by artificer
You should be able to feel pedal free travel as no resistance for the first 1/2' or so of pedal movement.
Does you pedal slowly sink down when you hold foot force on the pedal & is that when the fluid comes out?
If so you have a bad primary cup in the master cylinder.