How to Replace a Brake Master Cylinder in Your Car (Bleed Brakes)

one, two, three, four!

Rev up your engines!

It's time for the Scotty Kilmer Channel, is your brake pedal sink to the floor

when you step on it, then stay tuned on this frosty morning because I'm going to

show you how to fix it, if brake pedals start sinking, that means there's a leak

in the system somewhere, so get a jack, and pull off all four wheels to see if

it's leaking at any of the wheels, pull off the tires and look at the brake

system, this is completely dry so it's not leaking, and the back wheel brakes

were dry too, so they're not leaking, and since none of the rubber lines are leaking

either, that leaves the brake master cylinder,

the brake master cylinder often leaks inside itself, so you lose pressure

and the pedal goes to the floor, now to remove the brake master cylinder, you

need a special wrench like this, that has a little hole in the top, so it fits over

the line, it's a 10 millimeter on this Honda, you place it on top of the bolt

and then whack it to get it loose, then the rest you can just spin with your

hand to get the line off, and off it comes, then of course remove all the

other brake lines from the master cylinder too, then get a socket wrench, it's

12 millimeters on this Honda, and take the two bolts off that hold it on, then

you just wiggle it, until it comes off, and in this case we know the master

cylinder is bad because you can see it's been leaking on the back of the seal all

the crud is there, now here's a mechanic's tip, buy a brand new master

cylinder, don't buy a rebuilt one, I've had problems with rebuilt over the years,

and I don't use them anymore, now you just get the new master cylinder, put it

in place on the two bolt holes, it just slips right on, and then you put the

washer and the bolt on that holds it in place, and get them nicely tight with

your socket wrench, and now comes the tricky part,

you bleed the air out of the system, first pour the brake fluid in, and then

put the brake lines on, but only put them on loosely, so they're not tight, now

being a professional mechanic, I have power tools to bleed out brake systems,

but hey, you can use a giant screwdriver and do a good job all by yourself, you

just get your giant screwdriver, put one end on the brake pedal, push it down and jam

it against the seat, then push the seat up as far as it goes, that's the same as

pushing your foot on the brake and it builds up pressure, then with the pedal

push down, tighten the lines up as tight as they go,

just keep tighten them till you can't tighten them anymore, then once all the

lines are tight, take the screwdriver out, then you loosen the brake lines again,

and stick the screwdriver in, and push the seat up again, and just repeat this

process four or five times and all the air will be out of the master cylinder,

and now we've got a nice hard brake pedal,

that stops on a dime,

so the next time your brake pedal is giving you that sinking feeling, fix it

yourself, and remember if you've got any car questions visit Scotty