Fluid leaking from master cylinder filler plug vent

Rebuilding, adjusting, maintaining & alternatives
Hi guys,
I’ve just finished fitting the Grumpy disc brake kit, and a remote servo to my pick up, I modified the master cyl as instructed in the kit. I bled the system thoroughly this afternoon, but the pedal is very spongy and if you pump it a couple of times, brake fluid leaks out of the vent hole in the filler plug. I’ve checked the system and there are no leaks, the rear shoes are adjusted correctly and the hoses are in good condition, the front ones are new.
Any idea what could be the issue.
Any help gratefully received.
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spongy brake feel is a common occurence when 1st installed, try it, somewhere quiet, and see if it improves, leaking from resevoir have you fitted a remote filler, if so you need to blank the hole, as remote will now be higher,

if not you have probably overfilled it,

When its done its done (for now)
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Thanks very much for your help, having looked this evening, I have definitely over filled the reservoir ( I haven’t fitted a remote reservoir), it’s up to the bottom of the thread rather than 1/2” down from it like it shows in the manual.
Once I get it started ( as per my other issue ) and check the servo, I’ll try the brakes properly as you suggest and see how it goes.
Many thanks again.
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Joined: Fri Feb 05, 2016 8:20 pm

United Kingdom (uk) UK Lancashire (lk)

When adding a remote res the vent hole in the original cap must be plugged.

If the pedal is spongy there is still some air in the system. If by spongy you mean there is too much travel you may need to add some residual check valves to the system after the servo and as close to the servo as possible. You will need 2 psi for the front disc brakes and 10 psi for the rear drum brakes. That will bring the pedal up.

Also the pedal feel will be different with a servo added. If the pedal is just different neither of the above will change that feel.

Willwood 260-13783 2 psi.jpg
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