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Losing brake fluid

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MartyK Martin Kamin
Coral springs, FL, USA   USA
I cannot find a leak. I suspect that it is being burned after being sucked Into the engine from the servo but I am not seeing tell tale white smoke at the exhaust. A year ago I switched from Castrol to Valvoline DOT 3&4 fluid. I rebuilt the servo and believe I did a proper job but I wonder if I may have installed the rubber seals on the servo piston incorrectly. Please help with thoughts and ideas. Marty K

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petnatcar Avatar
petnatcar Silver Member Peter Carbone
Watertown, NY, USA   USA
Martin,

Have you looked up under the dash where the pedals connect to the Master Cylinders?

If it's wet around the rod and rubber cover (like my Clutch rod) then you may need a new MC.

Good luck,
Peter


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layaj2 Andy Lay
Bisley, Surrey, UK   GBR
Good call from Peter. I had that with my clutch master cylinder. Fluid all around that area and on the carpet, not noticeable at first under the mat.

Andy

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Drone Dog Avatar
Drone Dog TL Wright
Seaford, DE, USA   USA
i just noticed the same thing on my car. but i do not have the servo. on my winter check list, both the clutch and brake reservoirs were down about a qtr of the way from the top.

i went over all my connections and lines. i checked the pedal box. can not find any leaks. since i just put all of mine together with new masters, lines, etc, i am hoping the system just worked some air out of the masters that i did not get. i refilled and plan to check before each drive for a while.

sliproc Avatar
sliproc Kevin Quistberg E
Long Beach, CA, USA   USA
Martin,

Another place where you can lose brake fluid is the wheel cylinders in your drum brakes. It can leak onto your shoes and be burned off during normal braking or leak down onto the wheels or even onto the floor if it's a bigger leak. I'd pull the wheels and drums and check the wheel cylinders, they should be dry.

Jack T Avatar
Greensburg, PA, USA   USA
In reply to # 209126 by MartyK I cannot find a leak. I suspect that it is being burned after being sucked Into the engine from the servo but I am not seeing tell tale white smoke at the exhaust. A year ago I switched from Castrol to Valvoline DOT 3&4 fluid. I rebuilt the servo and believe I did a proper job but I wonder if I may have installed the rubber seals on the servo piston incorrectly. Please help with thoughts and ideas. Marty K

The servo cannister can hold a fair amount of fluid, and you might not notice a small amount that's being drawn through the intake.

MartyK Martin Kamin
Coral springs, FL, USA   USA
Thank you guys for all your help. A good look at the carpeting below the brake and clutch pedals showed enormous discoloration which was hidden below a floor mat. Apparently, my switch from Castrol to Valvoline 18 months ago must have killed the rubber seals in both(could it be just age?). I will replace both. Pretty sure this is the cause of the disappearing fluid. I will report back with results.

RAC68 Avatar
RAC68 Raymond Carbone
NJ, Jersey Shore, USA   USA
Way back in the late, 1980s before I switched to DOT 5 Synthetic, I had a similar issue. I was loosing brake fluid without any telltale indications and was totally frustrated trying to solve the mystery. About the same time, I decided to rebuild my brake servo as the amount of pressure required to stop seemed to be increasing and the servo non-existent. when taking the servo apart, I found the missing brake fluid had filled one side of the air chamber. It turned out the seals in the servo were leaking and the chamber was large enough to hold all the missing fluid.

The Servo is always a possibility where fluid is missing without trace.
Ray(64BJ8P1)



Edited 2 time(s). Last edit at 2019-02-12 02:52 PM by RAC68.

MartyK Martin Kamin
Coral springs, FL, USA   USA
Thanks again for the feedback. I have had the servo off recently because of leather strap binding. The canister was dry. In this case because of the major carpet discoloration, and residual fluid at the brake and clutch rubber boots, I am pretty sure it's the master and clutch cylinders. Because they are both over 50 years old with the fluid change it is a safe bet.

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