as the title say, from about 8 months i have a leak on the brake system that i have not been able to trace. Cylinder and all lines are dry, removed the 4 calipers to inspect but no sings of any fluid on them

Brakes are working as good as always but after i top up the reservoir, it will go below the fill line in about 2 to 3 months.

Been reading some and from what has happened to others i am fearing that this is a master cylinder leaking into the brake booster.

What i am looking here, replace the master cylinder and thats it? or by having fluid going into the brake booster I can consider it damaged as well?

I will work on the truck next weekend to confirm this but would like any upfront advice from you guys if possible

 

Yep, you nailed it. Brake booster may or may not be bad, but brake fluid is corrosive. Corrosive may not be the right word but you get my drift...

 

Is fluid running down the front of the booster? Loosen the nuts on the booster a few turns and check for fluid. If the MC is leaking internally, you would feel it in the brake pedal. If not, it may be time to replace the brake pads.

 

this morning and i removed the two nuts that holds the cylinder to the booster and separated it.

yes, brake booster is a bit more than half full with brake fluid. No leaks anywhere so far.

so, at the end, shall i just buy a new master cylinder, drain the brake booster and test it? or i might be better off replacing both?

 

Replace both. Check around, there are places that rebuild boosters, for much less than new.

 

Rock Auto sells reman boosters and master cylinders. However, a new M/C doesn't cost much more.

 

I fully concur with aussiekeeper.
The Booster is sucking the fluid out of the Master-cylinder, So Replace BOTH.

 

And when it comes to brakes, replace things in pairs. Rotors, pads, the such. Caliper bolts may be the only exception in pair replacement. Definitely do both boosters.

 

There should be one master cylinder and one brake booster. They mean replace both since the master cylinder is having fluid sucked into the booster

 

oohhhh well.

currently ordering both. Will be replacing them next week

 

don't waste your money. The booster is fine.

All the components in the booster are compatible with brake fluid for the obvious reason that there will always be at least a couple drips of fluid in the booster.

And the comments about the booster causing the MC to leak are ridiculous. (almost as ridiculous as the comment to replace both boosters)
Yes, technically the vacuum in the booster "sucked" the fluid out of the MC, since chances are the rear seal would not leak unless there was vacuum on the back side of the seal.
But this is not a failure of the booster. The booster requires vacuum to perform. That's why its called a Vacuum Booster.

If I were you, I would just replace the MC (either the piston or the rear seal went bad) and then while you are replacing it unbolt the booster and dump the fluid out (or use a tube and suck it out). While the fluid won't damage it, its not good for the booster performance to have the fluid in there. Especially on cold days.

And it wouldn't be good to slosh the fluid up and get it sucked into the engine...

But its up to you - listen to someone that designs and tests these products, or listen to people that think there are 2 vacuum boosters in your truck.

 

Man, you should have chimed in before, by the time i read this i had already gotten a new booster. Ohhh wel 70 bucks that i could have saved....

The worst part is that while installing the booster, it seems that i screwed the vacuum line that goes to the back of the engine and i cant figure out how to fix it...

https://www.f150online.com/forums/v8...ml#post5066364

 

Thanks for the correction and knowlege John.

Calm down Nancy, just suggesting to replace things in pairs.

 

Sorry, don't know much about the other end of the vacuum line. Hopefully you found the connection point already and you could reach it!


Ignorance and Arrogance.
Maybe you should work on replacing that pair

 

Not sure if yours falls into this one without a vin but check out this recall 20S31 for a master cylinder recall