rev up your engines today I'm gonna show you five reasons that your brake pedal
can sink when you step on now a sinking brake pedal is a scary thing you step on
your brakes and a pedal start sinking it's a very common problem and there's
five separate reasons for it I'm gonna explain them all right now, now the first
reason that your brake pelicans think it's cuz you have an external leak it's
leaking fluid that you'll be able to see somewhere some of your cars low like
mine you Jack it up in the air hey you got a truck or tall SUV you can just
crawl under there without jacking it up but this is love so we got a Jack it up
think of a nice strong flashlight so you can see it even blanked out the camera
but you want a strong one so you don't miss anything though with your
flashlight huh look inside at the wheels you can see there it's all bone-dry same
thing now where the brakes are it's all bone-dry there's no fluid leaking down
and of course do the same thing for the back brake check inside there too now if
you really want to do a good job you pull all the wheels off of course and
inspect them closely with the flashlight to see if they're starting to leak or
there's any fluid leaking you look at the brakes themselves and especially the
rubber hoses that feed them if you have an old car those rubber hoses can leak
too brake calipers leaking you can buy remanufactured ones
got an old car like this with drum brakes on the back the wheel cylinders a
leak and it'll be leaking inside there you replace the wheel cylinders and like
I said the hoses themselves can be leaking these are all external links
that you'll be able to see you see wet fluid and then you put your finger on
it's all slimy like brake fluid you know you got to fix that leak first and
that's what's making it sink cuz you losing pressure now the next thing to
check for is a brake fluid leak that's not external but internal the system is
leaking and you're losing fluid to check the brake master cylinder here to find
it's getting low on fluid sometimes the brake light will come on but try as you
may you can't see any leaks where you losing fluid you can't see any leaks then the
master cylinder would be leaking some say scotty if it's leaking how come I can't
see it well that's because the master cylinder bolts
to the brake booster and if it leaks it can leak on the back seal of the master
cylinder and then the fluid will drip inside the booster which is a sealed
unit now on this matrix you can easily see it there's a master cylinder it bolts to
the brake booster which is this big round black thing it will leak inside
here this is a sealed unit you won't see the fluid the only way you can see the
fluid is when you pull the master cylinder off and bolt out you'll see
that the brake booster here will have fluid inside it there's not supposed to
be anything inside the brake booster except air you start your car you get
vacuum pressure the vacuum hose goes to the booster and it gives you boost and
it's all just a bunch of air and when it's sucked out that gives the extra
pressure to boost your brakes stops your pedals sinking and you're losing brake
fluid but you can't see leak anywhere pull off the brake master odds are
you'll find the back of the brake master is all leaking and the booster has fluid
in it now since the booster is only made to have suction the rubber diaphragm can
be ruined if it's full of brake fluid so if it recently happened you take off the
brake master and you see it's leaking inside get any kind of suction device
suck all that blew it out of there you can spray some spray brake cleaner in
there and then suck all that out and put a new master on now some guys that are
worried especially on an older car if it did leak in there that will place both
the master and the booster together as a unit so they don't have to worry about
it being somewhat rotten and the booster and later it goes up that's a safer way
to fix that now the next way your brake pedal can sink is internal leaks that don't
leak out they don't leak out anywhere and you might think how can you have a leak
if it doesn't leak anywhere well the brake master cylinder is kind of like
your heart pumps fluid out when you stop on the brake pedal to the wheels but if
it gets an internal leak so when you step on it instead of the fluid going
from the master cylinder to the wheels it just leaks inside itself and it's not
leaking out anywhere but the pressure instead of going to the wheels just
either stays inside the master cylinder or goes back into the reservoir and that
reservoir hey when the master cylinder reservoir has fluid being pumped in it
it's not gonna leak out anywhere cuz that's sealed too so it'll just go up
and down when you stop on if you don't have any external weeks but your
losing pressure you see the master cylinder isn't losing fluid it doesn't get the
whole point that means odds are your master cylinder itself is bad and
leaking inside itself and there's a good way to test it you're not losing any
fluid but with the car turned off you step on the brake pedal and it sinks all
the way to the floor that tells you you're losing pressure but since you
don't see any leaks anywhere odds are it's the master cylinder that's leaking
itself you don't start the car you just do it with the car turned off because
sometimes it's the car running when you step on the brake and it sinks all the
way down that's the sign of a bad booster you check that a different way
with a bad booster when you step on the brake with the car turned off it might
be rock hard but then when you start the car and then step on the brake pedal and
it sinks all the way to the floor that shows that the booster has a problem
then it's sinking to the floor with the booster and in that case if it was hard
with the engine turned off but soft turned on you got a bad booster now the
fourth thing that can make your brake pedal sink are loose parts on your brake
system I've seen it where guys worked on their car and they didn't tighten up
either the hub when they were changing wheel bearings or you didn't get the
caliper bolts on that hold the brake caliper on right and it gets loose then
you're gonna have loose parts and the pedal will sink and if you have a car
with drum brakes like this matrix that has disc in the front but drums in the
back if the drums are worn or the brake shoes are worn and not adjust the tight
it'll sink because there's too much play when you stop on the brakes instead of
going a little bit they have to go a lot and I mix the brake pedal thing so you
check to make sure they're adjusted right and that they won't just all worn
out and worn tires hey that's the easiest thing to check you just pull off
wheels and see if things are worn out and if I were not you replace it it gets
hard you know while that pot was too worn it was causing too much play that's
the absolute easiest thing to check aside from just purely three pull up the
wheel you see the fluids leaking all over the place you know you need to fix
that leak now the fifth and last thing getting cause brake pedals to sink it's
probably the most expensive and hardest one to figure out when you go under the
hood and go over here you see all this crazy-looking stuff
well that's the main actuator for the anti-lock brake system and a problem in
your anti-lock brake system can also cause the pedal to sink
that can get expensive it's all computer run when you slam on your brakes
anti-lock brakes does exactly what it says it keeps your brakes from locking
up so if the sensors on one wheel shoulder it's slipping and the other one
isn't then it's got a actuate valve so that they all stop evenly so the car
doesn't pull and slide all over the place well it's all fine and dandy when
it actually works when they break the valves inside that modulator can go bad
and they can stay open when they're supposed to be open which makes the
pedal go to the floor things up they're supposed to pulsate they might pulsate
at the wrong time or not pulsate at all and you can get a dropping pedal now if
you get a dropping pedal and your abs light comes on that's on you there's an
ABS code on you got to get it scanned with the scanner and see what the
problem is if you do have an ABS problem and does sink to the floor generally
it has to do with that entire ABS actuator module going bad in a case of
this Lexus a new one is over 1,500 bucks so it's not something even worse you on
your worst enemy you don't want to have a problem with ABS modulator that's an
expensive problem now generally they are hard to diagnose spot often when these
go bad you will get an external leak you'll see this assembly has fluid
leaking out of it and it should be bone dry so if you see fluid leaking out of
it you know the modular starting to go bad no case you in the past I got
clusters where the pedal doesn't sink but they're losing fluid and you look at
that ABS module and you see it's starting to get a little bit wet well if
the brake pedal doesn't sink but you losing some fluid and you see it leaking
air you don't see leaks anywhere else hey truthfully I've had customers when
they find out they want to spend 1,500 bucks they buy canta brake fluid and
when it gets a little low and a light comes on they pour some back in and they
drive them yours that way sometimes if it's just the tiny little external leak
of a gasket or something seeping hey a lot of guys will just live with that and
add fluid as long as the pedals not sinking up it starts sinking yes kind of
replace it or get another car if it's that expensive so now you know the five
reasons that your brake pedal can start sinking to the floor and how you can fix
such problems or at least keep them under check so they don't cause future
problems or make you spend all your money fixing them
and here's some bonus questions and answers William the Concord says Scotty
helped me I got an 05 Toyota Tacoma v6 it won't start and I know a
little bit all cars it has no injector pulse and there's no ground to the fuel
pump and the wires and powers or grounds are okay everyone can check help you got
no injector pulse on one of those and all the grounds and the power wires are
good unfortunately this is a rare occasion but odds are your main computer
is gone your PCM the power control module is probably shot that's the only
reason I've ever seen him not having injector pulse on that particular
vehicle it is 15 years old now it's a rarity that the computers go bad on
Toyotas but when they do exactly that I worked on the Lexus a couple years ago
and did the same thing and I had to replace the main computer
it just wasn't pulsing the injectors anymore it's a rarity but even the
Toyota Lexus products once in a while their main computers will go out and as
long as you're sure that you got power and ground going to the computer and the
wires are good odds are your computer's gone out cuz they do every once in a
while, so if you never want to miss another one of my new car repair videos
remember to ring that Bell