Q: my brake master cylinder leaks fluid but not all the time

asked by on February 15, 2017

If I drive the car regularly the brake fluid doesn't leak. But if I park the car for a day or so, I lose brake fluid. It looks like it is coming out of the cap on the reservoir. I assume if there was a break in the reservoir it would leak all the time. Is the system pressurized and somehow forcing the fluid out? The fluid seems to only go down to a point where the brake light goes on in the dash. I'm stumped.and hope you can help. Thanks Doug...

My car has 46000 miles.
My car has a manual transmission.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $70/hr

What others are asking

Check Engine code P0128
The cooling system temperature is regulated by thermostat, and the cooling fans order to keep it at optimal temperature for the motor to operate. It does this by keeping the thermostat closed and the fans off until the coolant reaches...
Engine shudder while driving, burnt rubber smell
Hello. Most of the time, this is the first indication that the timing belt is failing (https://www.yourmechanic.com/services/timing-belt-replacement). The timing belt needs to be checked to see if it is going bad. If the belt is fine, then you may have...
Using E-15 fuel in my car do I need to use regular unleaded fuel maybe once in awhile or is it safe to continue to use the E-15?
E-15 is shorthand for gasoline blended with 15% Ethanol which is a fairly corrosive material which can cause damage to rubber parts and other critical parts over time. Ethanol also attracts and bonds with water from the air, and that...
Cold Starting Problems
As a general rule, car engines do not like cold weather and do not do operate as well in cold weather. When you start your car in the morning and turn the key to on, the coolant temperature sensor immediately...
Antifreeze problem
If you are having to periodically add antifreeze to the cooling system, there could be either an internal or external leak. That would include a "leak" through a faulty radiator pressure cap, which fault in the cap, if the fault...
What is the cost to replace the car mirrors?
Billing question sent to CS for the cost to replace both the driver and passenger door mirrors on a Saturn.
I have an very bad oil leak.
The crankshaft seal (https://www.yourmechanic.com/services/front-crankshaft-seal-replacement) is in the area you are referring to. The crankshaft seal lasts maybe 100,000 miles or so. There are other gaskets and seals in that area that would have to be examined as well. If you...
Advancetrac light is on no power steering not working
Hello, thank you for writing in. The vehicle may be having issues with the electric power steering module and system. Luckily there is a check engine light on, which means there is an engine diagnostic code that has been set....
Is There a video showing how to do this
Hello, we do not have repair videos available at this time. We do offer the service to come out and replace the alternator for you, and you can find out more about that here (https://www.yourmechanic.com/services/alternator-replacement). Otherwise, look to the internet...

Related articles

A Buyer’s Guide to the 2012 Toyota RAV4
While While the Honda CR-V might have been the pioneer of the compact SUV market, there’s no question that the 2012 Toyota RAV4 is king of the class. Not only does the RAV4 come with your choice of either a...
The Best Used Cars to Buy If You're a Teacher
If If you are a teacher, probably foremost on your mind is getting to school on time. You would also probably like a used car that is easy on gas and not terribly expensive, and will hold your gym gear...
How to Replace the Headlights on a Toyota Prius
Your headlights are one of the most important safety components for your car. A broken headlight bulb can endanger yourself and others on the road.