"Bladder Style" Cap for Master Cylinders: Treadle-Vac & (maybe) manual

Posted by JeromeSolberg On 2021/9/10 16:15:09

Hi Folks,

I found this cap, available from many different parts stores that supply trailer brakes, fits (1.25-18 UNEF thread) in the Treadle-Vac master cylinder (I tried it), and I believe also in the manual master cylinders.

It has an integral bladder, so your master cylinder is sealed from the elements without inducing any suction. the total volume of the bladder I haven't measured, but it isn't enormous, so perhaps I would put the regular cap back on for a long trip.

Still - at least while the car is "resting at home", should help minimize water absorption versus leaving the system vented-to-the-atmosphere all the time.

Here is one source:https://trailerparts.com/tie-down-reg-master-cylinder-fill-cap-with-internal-bladder.html

Here's another:https://www.etrailer.com/Accessories-and-Parts/Titan/T4480701.html

Comments/Reactions welcome.

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