Master Cylinder failure(s)?

[Scotty_h]

I've been using the valvoline DOT 3&4 compound without mixing my brands.

My GF is now a pedal pushing brake champ. She shouts when she's got it pumped and lets me know when it's close to the floor so I can shut it. before it completely bottoms out. I run it through a clear hose so I can see the fluid/air and make sure that it doesnt suck air on the release.

OK, well. I can't justtify a third MC on this thing. Maybe I will take it to have it vaccuum bled somewhere. I can't help but think that I'm missing a key point as to what happened to it to make it do this in the first place.

Thanks Nissanh for all the time put in on the head scratchin.

 

[Scotty_h]

-UPDATE-

OK guys, so just got done driving the truck and the brakes seem to have cleared up thier issues.
-What then, you may ask, was the problem?.. oh, I'll feed you baby birds,
Seems that all of my issues cleared up once I replaced the brake hoses (likely rear) that may have caught some strain while in my garage on a drooped rear axle.
My thoughts- possibly small cracks throughout the strained line formed allowing for really small amounts of expansion to occur under load?...:shocked:

That's what I'm going with.

Thanks everyone for the suggestions and the, what seems, ulimate correct answer.

The brakes now feel slightly underpowered which I am going to attribute to the 285's. I feel more mods on the horizon.

 

[LittleCaesar]

Good to hear Scotty_h. When the MC goes bad, the pedal is usually on the floor. At least that has been the case for the four I have changed out in my lifetime.

Now get some 199mm Tundra brakes for your ride sometime in the future.

 

[Scotty_h]

Haven't decided if I'm gonna go 199's or if I'm gonna do spacers for the 231's. I do tow, alot during the summer. On the fence about it

 

[Hunter89]

I know this is an old thread, but I seem to be having a similar problem. I'll start from the beginning. I bought my 97 4runner in March 2017. It was completely stock. As soon as I got it I did the usual maintenance, full tune up, tranny flush, smog (CA sucks), just to make sure everything was in good shape. Then I started adding the fun stuff, 3 inch lift OME in the rear and eibachs up front all on some bilstein shocks. When I did the lift, I also installed wheeler's offroad extended steel braided brake lines. I installed everything, bled the brakes and got some bfg km2's aned and alignment. Everything seemed to be fine, however my buddy also has a 97 4runner and I drove his and his brakes seem different than mine, they engage way sooner, and pedal doesn't go as far as mine. Since I got the lift and bigger tires I decided it was time to upgrade the brakes, so I got some ebc stage 3 slotted rotors and greenstuff pads. Installed them and when I test drove it, it didn't engage as well as I expected. I didn't really worry about it too much since it still stopped and my 4runner isn't my DD. I would drive it a few days a week to the grocery store and to the gym. I went to the mountains one day to go hunting and as I was going down the hill I quickly realized that my brakes weren't engaging as they should. I had to very forcefully push the brake pedal to engage the brakes! then on the way home all of the sudden my brake light on the gauge cluster would flicker sporadically. So this weekend I got a brand new Master Cylinder from O'rileys, (Couldn't afford OEM). I bench bled it before I installed it, I used dot 3 brake fluid, I bled the lines extensively in the sequence that is recommended Passenger rear, driver rear, passenger front, driver front. While I was bleeding the brakes, the pedal got really hard so I got excited that may have solved my problem, unfortunately it hasn't! I'm getting extremely frustrated, brake systems are supposed to be simple, and I've never had this much problems with brakes in my entire life. I've owned about a dozen vehicles, including 3 toyota 4x4's. I wonder if anyone has had this issue and actually resolved it? I'm a college student with a part-time job trying to raise a family so I don't have the money to keep throwing parts at it, I just want to be able to drive my 4runner. At this point it is undrivable. Also after I installed the new MC the brake light on the gauge cluster stopped lighting up sporadically.
TIA!!!

 

[Zcarjoe]

Awesome thread.

I just did the same with OME 906 and 1.5" spacers and have THE SAME ISSUE. Was about to go buy a new MC and read this. The rear line is the only original line left so SS it is. Hopefully that does it.