brake problems

[tjhaf2007]

So I was driving my 2007 4wd limited 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 press harder on the pedal and it was a repetitive cycle, all the way until the point of my pedal touching the floor. i was keeping constant normal pressure on the pedal, it seemed as if there was a pressure leak, so i checked my fluid levels, and they were good. i have no idea what it could be, im assuming its has to do with the master cylinder assembly. this is the first time ive noticed it and it was doing it on the way home from work too. The only thing i did brake related was spray brake clean on the rotors and pads to clean them. yesterday i cleaned my throttle body and maf. but thats it. i was planning on bleeding my brakes soon, but its not a spongy feeling. any ideas on how to check to see if it my master cylinder or something else without taking it to a shop or dealership??

 

[tjhaf2007]

and there arent any vsc or abs light on.

 

[earthrealm]

most likely a leaking/failing MC, blackworks has lots of experience on this, he should chime in soon

 

[BlackWorksInc]

Unfortunately it does sound like there's some sort of internal leak. I would try and inspect all your brake lines, check the fluid level, ect. for leaks/buldging lines. If you double pump the brakes does the pedal get stiff and then slowly bleed off like you're saying it does? This sounds similar to what happened to my unit, the internal piston seal developed a nick/imperfection and was bleeding fluid pressure internally.

 

[tjhaf2007]

Unfortunately it does sound like there's some sort of internal leak. I would try and inspect all your brake lines, check the fluid level, ect. for leaks/buldging lines. If you double pump the brakes does the pedal get stiff and then slowly bleed off like you're saying it does? This sounds similar to what happened to my unit, the internal piston seal developed a nick/imperfection and was bleeding fluid pressure internally.

thats what i figured, if you pump the brakes some, and then hold the pedal down, you can here a leaking sound. it sounds like fluid is bypassing something in the master cylinder.

 

[DC runner]

That bypassing noise is usually a blown gasket.

 

[tjhaf2007]

That bypassing noise is usually a blown gasket.

what gasket?

 

[tjhaf2007]

ive concluded that one of the seals in the master cylinder has gone bad. and since i dont have the cash right now to buy a brand new abs brake booster unit, i bought a used one online for about $350 shipped to my door. my next step is to find a shop or place that will let me use their scan tool to bleed my brakes. i used a genesis scan tool to bleed the brakes on my old 2003 2wd, its so much easier to bleed the 4runner brake systems with a scan tool; that's as long as nothing else is wrong with the brake system. i heard the naval base in town has a shop that i might be able to use. i guess you can rent out a bay with a lift and they lend out some of the specialty tools and stuff. so im gonna check to see if they have a scan tool and bay i can use to swap my new abs brake booster unit and bleed all my brakes and stuff.

 

[Velonici]

ive concluded that one of the seals in the master cylinder has gone bad. and since i dont have the cash right now to buy a brand new abs brake booster unit, i bought a used one online for about $350 shipped to my door. my next step is to find a shop or place that will let me use their scan tool to bleed my brakes. i used a genesis scan tool to bleed the brakes on my old 2003 2wd, its so much easier to bleed the 4runner brake systems with a scan tool; that's as long as nothing else is wrong with the brake system. i heard the naval base in town has a shop that i might be able to use. i guess you can rent out a bay with a lift and they lend out some of the specialty tools and stuff. so im gonna check to see if they have a scan tool and bay i can use to swap my new abs brake booster unit and bleed all my brakes and stuff.

If its anything like the 5 or so bases I was on, then they will have very basic tools. They might have a OBDII scanner if your lucky.

 

[earthrealm]

just back tracking: prior to this, how was your actuator/abs pump behaving?...was in pumping/kicking in every 7 to 15 secs if your foot is on the brake pedal? or every 1 to 3 mins if ur car is idling with your foot off the brake pedal?

 

[tjhaf2007]

I thought normal. The vehicle would shudder upon hard braking. I thought warped rotors, but I couldn't feel it in the pedal. I'm still trying to get adjusted to the differences between my old 2003 sr5 2wd to my new 2007 limited 4wd. I drove it stock for about 1 week and then threw the lift that I had just put on my old 2wd. I swapped the suspensions between the 2003 2wd and the 2007 4wd. Then I got an alignment and new tires on the 2007 4wd. The tires got mounted Monday last week. I havent had a bunch of time to get accustomed to the way the new one handles. I didn't really notice the pump running or not. I didn't pay attention to it.

 

[tjhaf2007]

Im still waiting on the other replacement unit in the mail. should be here next tuesday. anyways, i haven't noticed the brake issues lately, its acting normal and it stopping and staying stopped.

as of right now, im just going to flush out the old brake fluid and just try all new fluid for now. if nothing changes between now and when the replacement unit arrives, and if the old unit seems to be acting fine, i will just send back the one i ordered and not worry about swapping it.

any ideas as to why it would act up randomly and then be fine all of the sudden, makes no sense to me.