Losing brake fluid but no sign of leak

if you have a hydraulic clutch ( no transmission offered) check the slave cylinder for leaks ( some cars use the brake master cylinder as a reservoir for the hydraulic clutch)
check the brake booster to master cylinder mounting for leaks or the rear seal of the master cylinder may be faulty allowing fluid to pass to the booster chamber
check for a leak under pressure at the rear flexible rubber hose from the body on

The white smoke has nothing to do with the brake fluid loss. Look around the brake master cylinder, brake lines and joiners and brakes for signs of moisture. They should all be clean and dry any build up of dirt could be a hydraulic leak. The white smoke is more likely from warn valve guides.

if you have no indication of a brake fluid leak then you may have a bad master cylinder that has an internal leak that is losing brake fluid and being burnt (sucked into engine)by way of the power brake booster. if you undo the master from the power brake booster and move it ahead enough to see if it is damp were it bolts to the booster then you have a defective master cylinder.

Look at the insides of the wheels from under the car and look for a wet wheel. Check around the rear of the brake master cylinder for signs of leakage. Sometimes the fluid will leak from the brake master cylinder into the brake vacuum booster. You would need to remove the master and check for fluid in the booster.

It's a sealed system, so it's got to be going somewhere, leaking somewhere (or boiling off from severe braking operations over and over). Since you likely haven't experienced extreme braking, it must be leaking somewhere.
You will have to trace all your brake lines from the master cylinder to each wheel to check for any sign of leaking. Front calipers are easy to spot leaks when they leak. If you have drum brakes on the rear, you may need to pull off the drum to check the wheel brake cylinders. Peel back the rubber boot on each end of the wheel cylinder and look for any fluid leaks there.
Another place to check is at the back of the master cylinder. If a seal is bad there, it has been known to leak fluid inside the car, under the dash. Feel around the carpet under and behind the brake pedal for any wetness. If you find brake fluid there, you will need the master cylinder replaced or rebuilt.
Hope you find the problem. Don't forget to check the ABS system and brake lines, too.

Hi, you are right the rear is for the rear,the best thing is to pull both rear wheels off and remove drums that way you are looking at the wheel cylinder and then you will know if that is your problem,some times when they leak you cant see it with out pulling drums off. If no problem there check around master cylinder for leaks and around brake booster inside truck. Then if you still have no sign of fluid take the two nuts off master cylinder and see if leak is in side booster is wet.
If need more info please re post.
Thanks dodge tec

well if you are losing fluid you definatly have a leak as brake fluid is not a "topping off fluid". you could have a leaking master cylinder either externaly which can be seen on brake booster or it can be leaking into the brake booster filling it with fluid. other than that you also may be leaking from your brake hoses(one hose at each wheel), calipers(front wheels and rear if all wheel disc brakes), wheel cylinders (if you have rear drum brakes), or metal brake lines due to rust and corrosoin (run from master cylinder to each brake hose). please rate 4 thumbs if helpful.

Are you losing any Brake Fluid? Is it visible anywhere at the four wheels? Is it visible anywhere else?
The Master Cylinder may be defective. When you bled the Brakes did you maintain proper Brake Fluid Level in the Master Cylinder? If you didn't: and air entered into the Master Cylinder there maybe air within in the system in the Master Cylinder. You can bleed the Master Cylinder by removing the brake lines, adding more fluid, pumping the brakes, bleeding the air out of the system.
Are you losing Brake Fluid and can't find a noticeable leak? Then there is a good posibility that the rear seal in the Master Cylinder is leaking and the Fluid is going into the Brake Booster - which is the large wheel shaped drum located on the fire wall. In this case both the Brake Booster and the Master Cylinder will have to be removed and replaced. The Booster contains seals that Brake Fluid is very caustic to and will ruin these seals- causing future failures.
If no Brake Fluid is lost, no leak found: Check the Brake Booster Vacuum Advance. This should be connected to the outside of the Booster, attached to a hose, with the hose going to the engine. Check to see if this is working properly. Replace if needed.

1. What is the Brake Fluid Level?
2. Are you losing any Brake fluid at all? Are there any puddles or noticeable wetness on the ground or on the tires/wheels? With vehicle parked, the reservoir filled (overfilled), and engine running: pump the brakes and check on the ground and back sides (inside portions) of the wheels. Look for any brake fluid leaks.
3. Leaks from Calipers usually means a leak from the caliper piston. The rubber seals will be wet.
Leaks from Drums usually means a leak from the wheel cylinder.
4. In any case of leaks from the wheels - replace the calliper OR wheel cylinder.
For caliper leaks: change the brake pads, and clean the rotors with brake cleaner.
For drum leaks: clean the drum and brake hardware with brake cleaner, and replace the shoes.
5. If no leak is detected from the wheel area's: check under the Master Cylinder for wetness indicating a possible leak.
6. If no leak can be found: you MAY have a rear seal leak in the Master Cylinder which is pumping Brake Fluid into the Brake Booster (that large disk looking thing attached to the fire wall, attached to the Master Cylinder in front).
a. Use a large drip/catch pan under the Van in the area on the Master Cylinder.
b. Disconnect the brake lines from the Master Cylinder using a flair wrench.
c. Remove the two nuts (12 or 13mm?) attaching the Master Cylinder to the Brake Booster. If you have been using a lot of fluid, and have found no leaks, here is a good possibilty that all that brake fluid has collected in the Booster; so when you detach the Master Cylinder from the Brake Booster, all that fluid will come rushing out!
7. If there is Brake Fluid inside the Brake Booster: there is no cleaning that out. Brake Fluid is very caustic to the seals inside the Booster and should be replaced.
8. Of course the Master Cylinder will also have to be replaced.
9. After replacing the Master Cylinder/Brake Booster - make sure you get all that spilled brake fluid off the engine compartment area parts! I use a brake cleaner, then mild soap and then water to rinse. Clean any Brake Fluid off Paint imediatley as it will quickly dissolves finishes and paint.
10. If no leak is detected and the Booster is clear, there may be problems with the Booster One-Way Valve. This is attached to the outside of the Booster and has a hose from an "advance" connected to it. This maybe malfunctioning where you are losing power. Replace this first before deciding to replace the whole booster (in cases of NON-LEAKS ONLY). If that did not work, there may be inner seals inside the Booster that have failed. That means a new Booster.
11. In any of the above cases: Make sure you bleed the Master Cylinder correctly and bleed the brakes (at each affected wheel) correctly. Any air in the brake lines will decrease your braking proficiency or could result in brake failure.

Let me know if this helped or if you have any additional information or questions. Feel free to contact me at FixYa.com!

if you can see a good amount of wet brake fluid between the brake master cylinder and the brake booster. and you have been adding fliud often,you could have a bad master cylinder. it has to be replaced not rebuilt. you however may have a far more common problem, a rusted through brake line.have someone pump the brake pedal, than look under the car for a brake fluid leak ,repair as needed. than bleed the brakes for a good hard brake pedal
good luck chris