my car is eating brake fluid

Cobra_Dusten · Jul 12, 2009

been in cali about 4 months, and about 1500 miles on the car, mostly city.
In that time the car has run the brake fluid resevior down to the point the light comes on twice. driving in traffic today the light was coming on while driving, but when i would hit the brakes it would go off. popped the hood, fluid is down again, but not that far. I have had my car on a lift twice and have been unable to locate a leak. I'm looking for some help on this, as i dont know what to do next. I am curious if my mysterious vacuum leak and 41/91 codes might go together with, and a leaking mastercylinder/booster?

stangster50 · Jul 12, 2009

Cobra_Dusten said:
been in cali about 4 months, and about 1500 miles on the car, mostly city.
In that time the car has run the brake fluid resevior down to the point the light comes on twice. driving in traffic today the light was coming on while driving, but when i would hit the brakes it would go off. popped the hood, fluid is down again, but not that far. I have had my car on a lift twice and have been unable to locate a leak. I'm looking for some help on this, as i dont know what to do next. I am curious if my mysterious vacuum leak and 41/91 codes might go together with, and a leaking mastercylinder/booster?

could be leaking into the booster from behind the master. and also could be wheel cylinders. you would be able to see the fluid coming from behind the drums. pull a drum off..

Cobra_Dusten · Jul 12, 2009

stangster50 said:
could be leaking into the booster from behind the master. and also could be wheel cylinders. you would be able to see the fluid coming from behind the drums. pull a drum off..

as much fluid as im leaking, if its a wheel cylinder it would be ****ing all over the drums. its emptied the master cylinder 2.5 times in 1500 miles. there is nothing on the brake system that is wet. im thinking its leaking back into the booster too. but i dont know how to check for it.

aar0s · Jul 12, 2009

i had a leak one time that drove me nuts itll i noticed that the front of the prop. valve was wet. had a buddy push the brakes and bingo bad valve. have someone push on the brake while you look under the hood, if you havent already.

stang&2Birds · Jul 12, 2009

aar0s said:
i had a leak one time that drove me nuts itll i noticed that the front of the prop. valve was wet. had a buddy push the brakes and bingo bad valve. have someone push on the brake while you look under the hood, if you havent already.

Good point. Many fox cars are well past the age where their prop valves start to leak.

Check the prop valve and the wheel cylinders.

Another good way to check is to get some cardboard, make sure ALL of the ground under the car is covered. Start the car (engine running). And hold your foot on the brake pedal for 5+ mins. See if there are any leaks. If not, try pump, hold for 2min, release, pump, hold for 2min, release, etc.

A pressure bleeder may help you find the leak. But, if it's something like the prop valve, then you may need the 1000+psi of a working brake system to produce the leak. Other than a prop valve that is just going, a pressure bleeder will often help to find a leak (just wait 10-30 mins with the system pressurized to ~25psi).

Good luck.

Cobra_Dusten · Jul 12, 2009

stang&2Birds said:
Good point. Many fox cars are well past the age where their prop valves start to leak.

Check the prop valve and the wheel cylinders.

Another good way to check is to get some cardboard, make sure ALL of the ground under the car is covered. Start the car (engine running). And hold your foot on the brake pedal for 5+ mins. See if there are any leaks. If not, try pump, hold for 2min, release, pump, hold for 2min, release, etc.

A pressure bleeder may help you find the leak. But, if it's something like the prop valve, then you may need the 1000+psi of a working brake system to produce the leak. Other than a prop valve that is just going, a pressure bleeder will often help to find a leak (just wait 10-30 mins with the system pressurized to ~25psi).

Good luck.

the wheel cylinders have less than 3000 miles on them, as they are new from when i went to 5lug. but, i will get a buddy to help me check by holding the brakes. but i have a hard time believing with as much fluid loss as i am experiencing, there is nothing wet.

aar0s · Jul 12, 2009

if its the prop valve, mine was spraying it on the header and it was burning off slowly, couldnt see the smoke and never saw it wet. I just happend to notice that the valve had fluid on it one day.

Mustang5L5 · Jul 12, 2009

Unbolt the MC from the booster and pull it forward. Look for wetness behind.

Usually you'll see the face and bottom of the booster is all rusted out as well

Cobra_Dusten · Jul 12, 2009

Mustang5L5 said:
Unbolt the MC from the booster and pull it forward. Look for wetness behind.

Usually you'll see the face and bottom of the booster is all rusted out as well

thanks.

7upstang91 · Jul 13, 2009

I had the same problem from the drums. Have you had any rearend work recently? After I had the 3.73s and upper and lower control arms put in the guy who did it forgot to hook up the rear brake line properly.

Darkwriter77 · Jul 13, 2009

Having a bit of the same issue, myself. Really slow leak, only goes down like 1/3 of the way in the reservoir over the course of two weeks or so of daily driving. I've checked all four wheels and followed the brake lines front to back without any signs of leakage, and as far as I can tell, there's nothing leaking around the proportioning valve or master cylinder. Never thought about it leaking directly into the brake booster, though - I might just have to unbolt the sucker sometime and see if that's where it's been going.

Cobra_Dusten · Jul 13, 2009

7upstang91 said:
I had the same problem from the drums. Have you had any rearend work recently? After I had the 3.73s and upper and lower control arms put in the guy who did it forgot to hook up the rear brake line properly.

i had new gears installed, an auburn, and 5 lug with ranger drums all installed. but, i did most of the work myself. this problem started a while after that work.

my car is eating brake fluid

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