2007 Brake Master Cylinder - the bad news

[skitown]

Ouch - just received the bad news from my local mechanic:
Likely need new Brake Master Cylinder;
And that he might be recommending that I take it to the dealer.

Found this description on a previous post - it is the exact same symptoms:

So I was driving my 2007 SR5 4wd today to get lunch, and while driving through town, i realized that every time i stopped for too long, the car would slowly start creeping forward and i would have press harder on the pedal​

This is my wife's 4Runner and I'm not a DIY auto guy.

Am I looking at a $3000 fix at the Dealer, because the part is $2000?

 

[Dominic]

If it creeps forward, and the air conditioner is on, that's to blame for it, usually, I've had mine lurch forward when it kicked on... I don't think you should put it all on the master yet, unless the ac wasn't on...

 

[nevada]

If it creeps forward, and the air conditioner is on, that's to blame for it, usually, I've had mine lurch forward when it kicked on... I don't think you should put it all on the master yet, unless the ac wasn't on...

or on defrost, as the AC is activated then as well.

 

[skitown]

Thanks for suggestion - but no - it happens all the time now.
Not associated with AC or Defrost.

Is 2007 SR5 4Runner with 105,000 miles

 

[chmura]

I read a post and it seemed like a very valid post.

The owner replaced all his brake lines to stainless steel brake lines.

This solved his creeping forward program.

Try to search this forum and you probably can find this post.

 

[m85476585]

I read a post and it seemed like a very valid post.

The owner replaced all his brake lines to stainless steel brake lines.

This solved his creeping forward program.

Try to search this forum and you probably can find this post.

I read that too, but it didn't make any sense to me. I don't see why brake lines should affect whether it creeps forward, unless the stock lines are really stretchy.

I guess it's worth a try since it's cheaper than a new master cylinder. You could also try bleeding the fluid in case air got in somehow.

Actually, I wonder if air in the system is why SS lines helped that guy. It just got better after installing them because it was freshly bled, not because the lines are that much different.

 

[blackoutt]

I would bet it was just the good bleed that helped that guy. Braided lines only help keep the pedal feel remain firm at higher pedal pressures, at a comparatively light pedal pressure just holding a stop the rubber lines shouldn't be a place of much system expansion unless there is a big bulge on one somewhere.

OP I assume you've already exhausted the obvious like pads and fluid and a good bleed?

 

[earthrealm]

what other symptoms are you having?......any high pitched beep from the dash?..can you feel the abs pump kick in when you engage the brakes?....

with the ignition on, depress the brake pedal a couple of times and see if the abs pump will kick in...........

 

[CookieRoe]

I read a post and it seemed like a very valid post.

The owner replaced all his brake lines to stainless steel brake lines.

This solved his creeping forward program.

Try to search this forum and you probably can find this post.

I read that too, but it didn't make any sense to me. I don't see why brake lines should affect whether it creeps forward, unless the stock lines are really stretchy.

I guess it's worth a try since it's cheaper than a new master cylinder. You could also try bleeding the fluid in case air got in somehow.

Actually, I wonder if air in the system is why SS lines helped that guy. It just got better after installing them because it was freshly bled, not because the lines are that much different.

post:

http://www.toyota-4runner.org/4th-gen-t4rs/181827-does-you-toyota-4runner-creep-forward-ac-@-traffic-light-best-$36-ever-spent.html#post1843388

Worked for [MENTION=93434]gshadow325[/MENTION] . I'll be installing these lines in the future.

 

[gshadow325]

Thanks for suggestion - but no - it happens all the time now.
Not associated with AC or Defrost.

Is 2007 SR5 4Runner with 105,000 miles

before i suggest you get a new mechanic, i need some back info.

when was the last time you check your brakes?
brake pads changed?
rotors changed?

go outside and look at the rotors and make sure you see shiny metal across the board on the whole sweep of the brake pad. you will need to check the inside pad too on both sides.

my truck in the beginning had uneven wear on the rotor surface. towards the end before i changed my pads, bigger rotors and bigger calipers....i suffered frozen calipers too.

almost everyone on here has a creeping 4 runner. some worse than others because of age of braking system. it annoyed the hell out of me, so i upgraded to fix my problems

 

[skitown]

Dealer Service Manager Fix - a work in progress

Here is my update - current situation:
My local mechanic diagnosed and recommended the Brake Master Cylinder change. And that it was a technical job requiring specific tools.
Recommended that I take to the Dealership.

I called the dealer service department and described the situation.
Dropped off the vehicle.
Got a call from the service manager: We recommend original Toyota Brake shoes. (Note - my local mechanic did the front brakes in April 2014.)

OK - if you think that will fix it.

Picked up the vehicle, took for test drive - did not fix.
Recommended that I "set the new brake shoes" for 300-400 miles.
OK - two weeks going by, shoes are not setting, car is still moving.

Here is a good description:

My driveway has a slight incline.
If I sit in the car, put it into reverse, and wait for everyone to get in.. it starts to roll. Need to push the brake pedal harder, or pump the brakes..

What does it feel like? If feels like it is losing pressure.​

I welcome your feedback and suggestions.

The dealer Service manager is supposed to be looking for a service bulletin for suggested fixes.

I'll send him a link to this post - for a good description and the community suggestions!

 

[kaizer427]

Here is my update - current situation:
My local mechanic diagnosed and recommended the Brake Master Cylinder change. And that it was a technical job requiring specific tools.
Recommended that I take to the Dealership.

I called the dealer service department and described the situation.
Dropped off the vehicle.
Got a call from the service manager: We recommend original Toyota Brake shoes. (Note - my local mechanic did the front brakes in April 2014.)

OK - if you think that will fix it.

Picked up the vehicle, took for test drive - did not fix.
Recommended that I "set the new brake shoes" for 300-400 miles.
OK - two weeks going by, shoes are not setting, car is still moving.

Here is a good description:

My driveway has a slight incline.
If I sit in the car, put it into reverse, and wait for everyone to get in.. it starts to roll. Need to push the brake pedal harder, or pump the brakes..

What does it feel like? If feels like it is losing pressure.​

I welcome your feedback and suggestions.

The dealer Service manager is supposed to be looking for a service bulletin for suggested fixes.

I'll send him a link to this post - for a good description and the community suggestions!

I really do not think you have a problem. I highlighted the suggested solution in red above.

 

[m85476585]

Maybe take it somewhere and have them bleed the brakes/ change the fluid. Or do it yourself, it's not too difficult.

Does it do this when the engine is cold, or when it's warmed up, too? When it's cold it will fast idle, which is surprisingly powerful in these vehicles.

How does the pedal feel? Is it hard like a rock, very soft (goes almost to the floor with light effort), or about normal?

 

[ChuckJ]

I have an 05 and wouldn't consider this normal..it sure sounds like a problem related to the master cylinder..you shouldn't loose brake pressure and have your foot slowly sink to the floor and then start rolling, not unless it were leaking out somewhere, and you would have figured that out by now by the fluid that would be in your driveway. To sink that much you'd probably need alot of air in the system but before you spend the big bucks, I agree with the previous post, I'd have somebody bleed them good (pretty cheap, any shop can do it as you said you're not a DIY guy), maybe you'll get lucky (hard to believe the dealer didn't do this first, or at all)...I never realized how expensive these master cylinders were til I just looked...wow, I guess its been a long time since I bought one, and that wasn't for a toyota.. good luck

 

[skitown]

Under normal driving, the pedal feels good.
Brakes feel good.
Stopping at a stop light, all is good.
But, while stopped and waiting for the light to turn green, my mind wanders and as my pedal pressure remains the same.. It starts to roll.
The brakes (not the pressure I am applying) starts to fail, bleed off, release.
Next thing I know, I'm rolling forward.
I then press further and harder to stop again.
the symptom repeats in about 5 seconds.

Feels like a vacuum leak.

 

[earthrealm]

:flock:

 

[nevada]

Under normal driving, the pedal feels good.
Brakes feel good.
Stopping at a stop light, all is good.
But, while stopped and waiting for the light to turn green, my mind wanders and as my pedal pressure remains the same.. It starts to roll.
The brakes (not the pressure I am applying) starts to fail, bleed off, release.
Next thing I know, I'm rolling forward.
I then press further and harder to stop again.
the symptom repeats in about 5 seconds.

Feels like a vacuum leak.

the mc is bad, its bypassing internally.

 

[emoore924]

you shouldn't loose brake pressure and have your foot slowly sink to the floor and then start rolling, not unless it were leaking out somewhere

Actually ^ this is exactly the symptom of a failed m/c and it doesn't have to have a fluid leak.

The m/c is a tube with a plunger in it that pushes the brake fluid out the brake lines when you step on the pedal. Stepping on the pedal pushes the plunger down the tube and out goes the fluid.

A good way to test the m/c is to start the car, then press **and hold** the brake pedal with some pressure for about a minute. You don't have to kill it.

If the pedal slowly goes to the floor, the m/c has failed because the seal on the little plunger is letting brake fluid leak past the seal and back into the reservoir instead of pushing it down the brake lines.

Happens all the time.

OTOH, if the m/c holds pressure (the pedal stays up) and you're still not stopping, something is preventing the fluid from getting to the calipers. One or more frozen calipers comes to mind but there are a bunch of things between the m/c and the calipers. So, i'd jack up one side of the truck, have an assistant gently press the brake pedal and see if one or more of the wheel(s) still turn. If so, the caliper isn't doing its job and you have to diagnose why.

Note: This is NOT a definitive test for a frozen caliper as the power from the m/c is pretty significant. Even a small amount of force from the m/c on the caliper might stop *you* from turning the wheel but could still allow a 5000 lb truck to move. Or, the caliper might be well and truly stuck so any amount of pressure from the m/c won't make any difference anyway...

 

[BlackWorksInc]

My old MC was actually leaking internally from developing a small tear/cut in the primary piston cup seal, I caught it before it resulted in brake failure though (I actually replaced the plunger assembly on my old unit to keep it as a back-up.)

 

[TumbaBurros]

Did you ever get this figured out?

I was chilling at a red light last thursday and the same thing happened to me.

The brake pedal started to sink and I started moving forward. I had to push the pedal almost all the way to the floor before it stopped. I almost hit the guy in front of me. I put it in neutral to pump it, but as soon as I let off the pedal and went to pump, it grabbed higher(where it normally does).

Hasn't done it since. But now I'm paranoid it will do this while I'm driving and not just idling at a light.

These 4Runners have a reputation of being reliable but it seems problems like this failing hydrobooster thing are quite common. What's the use of a reliable engine/tranny if replacing a part like this costs as much as an engine? Or the plague of 4Runner sticking calipers? Milk shakes in the third gens?

Anyways that's beside the point. Did you ever find out what it was or get it fixed?