runnermedic

as the title says
today while taking my daughter to the doctor,i passed the scare of my life.
i live in puerto rico so living in an island means uphills and downhills every where
but today my recently buyed 3rd gen 4runner wants to make a point,be quick!!!
yep while going downhill for about 10minutes i encounter this guy that turned to the left with out any signal and SURPRISE!!!!! NO BRAKES!! i couldn't stop at all
so i put it in low gear while usng the ebrake and i made it to safe zone,believe me i was really scare,thank god and the ebrake we make it alive.

ok now to the problem
when i stepped in to the brake pedal and realized there where no brakes i didnt left the pedal off and then there was that grinding noise (I KNOW ABS WORKING)
the pedal was touching the floor,no pressure at all then i tried to pump and cycle the brakes and nothing,i took a look to the,booster ,master cylinder,calipers ,fluid level,no leaks and everything was ok.
so i was thinking ,maybe brakes are ok and the problem is the abs system?
i took out the abs fuse (BIG 60amps fuse) and then the brakes started to work not right away but i took me nearly 5 minutes to build pressure in the system.

thank god again we made it home ,then in home and started to test the brake booster and master cylinder this way (tell me if i did it wrong)

1.while engine off pressed the brake i took 3 or 4 press to be like a rock.
2.let the pedal pressed for a few minutes and no loss in pressure
3.turn the engine on and pressure drop,pedal stays in mid travel,no loss of pressure.
4.while engine is running pressed the braked pedal a few times and pressure and rpms go up

i think brake booster is ok (no wet carpet)

master cylinder appears to be factory one (100000 miles on the 4runner)
1.no leaks
2.is building pressure quick
3.brown brake fluid (needs to be flushed)
4.some damp spots around the master cylinder and brake booster connection

any comments about this momentary brake failure?????

habanero

Did you overheat your brakes with contaminated fluid on the downhill?

runnermedic

the fluid is dark brown (contaminated) and about the brakes there was no signs of overheating no odor no smoke i even touched the rotors with my finger with out hurting it when downhill i prefer to use the tranny to slow down a bit and turning off the Over Drive
im going to loose a bit the MC and see if there is fluid in the back of it,anyway im going to replace it along with new fluid,shoes and pads
my worry is about the abs failing i don't want to suffer this again,so i think im going to leave the abs with out the fuse for a while

about the brake fluid ,regular dot3 is ok or not?

Texas_Ace

I am gonna guess that you boiled the brake fluid. If the brake fluid is dark brown then it have been overused/overheated quite a bit and can lead to this exact problem.

If it boils you will loose brakes until it cools back down which sounds like what happened to you.

I would start with a complete flush of the brake fluid system. Get a vacuum bleeder and bleed each wheel until the fluid runs clear.

Do this first, if you have to do something else to the brake system later and bleed it again that is good.

Dot 3 is ok but if you are getting the brakes hot on a regular basis Dot4 or 5 is better fluid that stands the heat better.

TheDurk

My understanding is that DOT 4 is backward compatible but that DOT 5 is not and can cause damage to DOT 3 systems unless completely flushed out and that different physical characteristics (compressibility) can cause problems with DOT 3 ABS systems.

Texas_Ace

I have heard this as well but have seen people use it without a problem in the past.

Generally you won't find DOT5 anywhere but online anyways so not a real problem. In this case DOT4 should work fine anyways.

runnermedic

ok guys
job finished
flushed the entire brake system twice until fluid is clear in all corners (DOT3)
replaced pads and shoes (maybe half life but just in case)
replaced the MC with a new one (found a small leak in the old one)
all hoses are ok no swells,no cylinder and calipers leak

system bleeded twice while engine is off
system bleeded twice with engine running(abs was storing some bubbles)
then again with engine off and on (what a pita)

brakes tested in clear road abs working ok
brakes tested in gravel abs working ok
ebrakes working ok

did i missed something?

i think today i deserve a corona extra!!!!!!!

the old MC

Texas_Ace

Sounds good, hopefully that should take care of things. I would drive carefully until you make sure they are working right and pay special attention to the brakes to make sure you don't feel any fade or other issues.

Drive like it is always raining out and test the brakes from time to time.

Be sure to bed the brakes if they were just installed.

runnermedic

yep
drive it like grand ma

Jomoka

There is also Dot 5.1. Which is as good or better than Dot 5 in terms of boiling points, but fully compatible (and mixable) with Dot 3 and 4.

Texas_Ace

I thought there was something like that.

Chrisblankenhorn

Came here to make a new thread, but looks like y'all can probably help....

My 98 4runner failed state inspection cuz I was missing a lug nut and stud on my front driver side wheel. I took tire off, brake pads off, and the caliper ( first time doing this, didn't know the correct process and I lost a lot of brake fluid ), when i realized that i had enough threads on the stud that was broken to fit a lug not on there, and I didn't need to replace the stud itself..I put everything back together, and yes, I had enoughs threads on the stud to put a new lug nut on.....

I put more brake fluid in, and went to drive it back to the inspection place, but now my brakes barely work. Feels like there is just no pressure there. I am not leaking any brake fluid, but no pressure is building and its just not safe...I carefully drove it back to the inspection place to show them that I put a new lug nut on there ( thankfully they didn't do the whole inspection again - or I would have failed the brake test ). I was able to drive it back, and I mean the brakes work, but not great at all. I had my hand on the ebrake at all times in case I needed it lol..

So what y'all think? I spent a couple hours looking around online, but never got a solid situation-specific answer.. Thanks!

Texas_Ace

You have to completely re-bleed the brake system once air gets into it. Get yourself a vacuum bleeder and go to town. You can find the process in the BGB.

Get your self a few bottles of brake fluid, you will need it. Also will need a friend to keep the brake cylinder filled, if it ever runs dry and gets air in the system you have to start all over.

You want to bleed the system until the fluid runs clean and no air is left. The pedal should be very hard when done.