[Saloon-lovers] Brake fluid disappearing

I have a 66 3.8S, brake fluid keeps disappearing from the
reservoir. Brakes have been done with rebuilt calipers front and
rear. Master cylinder was rebuilt. Funny thing I cannot find any
indication of a leak except the level keeps going down. The really
strange bit is that it goes down when the car is not being used and
has been sitting for a period of weeks, went from right under the
mounting band to about 1/2’’ above bottom. filled it up and I
noticed it was down about 2/3 over a period of a couple weeks.–
65 MKII, 66 3.8S, 67 XKE, 76 XJ6C
Reno, NV, United States
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Check the master cylinder for moistness. The carpet padding can absorb a
lot of fluid before it shows. If there really are no external leaks then I
would suggest it is leaking into the booster. When I took apart the booster
in my first car in 1969 it was 1/4 full of fluid.

Mike Eck
New Jersey, USA
www.jaguarclock.com
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2

I have a 66 3.8S, brake fluid keeps disappearing from the
reservoir. Brakes have been done with rebuilt calipers front and
rear. Master cylinder was rebuilt. Funny thing I cannot find any
indication of a leak except the level keeps going down. The really
strange bit is that it goes down when the car is not being used and
has been sitting for a period of weeks, went from right under the
mounting band to about 1/2’’ above bottom. filled it up and I
noticed it was down about 2/3 over a period of a couple weeks.

65 MKII, 66 3.8S, 67 XKE, 76 XJ6C
Reno, NV, United States

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In reply to a message from jagarra sent Sat 8 Jun 2013:

If you can not find it look first under and in your carpet under
the master cylinder. If that is dry it is in your booster and vac.
tank.–
The original message included these comments:

rear. Master cylinder was rebuilt. Funny thing I cannot find any
indication of a leak except the level keeps going down. The really


George Camp
Columbia SC, United States
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Its draining into the boost and from there to the exhaust. You
probably get white smoke when you start the engine after a couple of
days rest.

quoting jagarra luvewe@att.net:

I have a 66 3.8S, brake fluid keeps disappearing from the
reservoir. Brakes have been done with rebuilt calipers front and
rear. Master cylinder was rebuilt. Funny thing I cannot find any
indication of a leak except the level keeps going down. The really
strange bit is that it goes down when the car is not being used and
has been sitting for a period of weeks, went from right under the
mounting band to about 1/2’’ above bottom. filled it up and I
noticed it was down about 2/3 over a period of a couple weeks.

65 MKII, 66 3.8S, 67 XKE, 76 XJ6C
Reno, NV, United States
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In reply to a message from Thaddeus Dabrowski sent Sat 8 Jun 2013:

Thanks guys, you confirmed my suspicion, checked XKs, kit
is about $360, rebuilt unit around $500.

I figure there is a hole in the diaphragm, and the stored
vacuum in the tank is sucking it out of the reservoir.
Wonderful, got a show next weekend, luckily I am just
displaying the old girl, so will add fluid.

regards,

gerard–
The original message included these comments:

Its draining into the boost and from there to the exhaust. You
probably get white smoke when you start the engine after a couple of
days rest.


65 MKII, 66 3.8S, 67 XKE, 76 XJ6C
Reno, NV, United States
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In reply to a message from jagarra sent Sat 8 Jun 2013:

I figure there is a hole in the diaphragm, and the stored
vacuum in the tank is sucking it out of the reservoir.

gerard,

How is your handbrake ? If you are losing fluid to the
inside of the booster, the leak is in the hydraulic side,
not the air side. Since this car only has a single circuit
brake system, a leak can cause complete brake failure. When
this happens, and your foot goes to the floor, remember to
override your instincts and release the pedal, and pump it.
Or fix the problem before you drive it anywhere.

Paul–
The original message included these comments:

In reply to a message from Thaddeus Dabrowski sent Sat 8 Jun 2013:
Thanks guys, you confirmed my suspicion, checked XKs, kit
is about $360, rebuilt unit around $500.
I figure there is a hole in the diaphragm, and the stored
vacuum in the tank is sucking it out of the reservoir.
Wonderful, got a show next weekend, luckily I am just
displaying the old girl, so will add fluid.


PS
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In reply to a message from jagarra sent Sat 8 Jun 2013:

I had my Mk2 booster rebuilt by power brake exchange, San Jose Ca
and I recommend them. The rebuild of my booster was LESS than the
cost of a rebuild kit from the usual vendors. My album has some
pixs. Pete–
Pete55Tbird
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In reply to a message from Pete55Tbird sent Sat 8 Jun 2013:

Joecurto.com rebuilt mine for a decent price and quick enough.
P.–
Peter J. Smith, 1966 3.8S MOD
Carson City Nevada, United States
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