91TPU

so im driving the runner today, coming to a stop and boom brake pedal hits almost goes all the way to the floor. seriously i almost crapped myself when it happened. even with it going to the floor i still had just as much braking power, but the pedal just traveled much farther. it would occasionally not go all the way to the floor on the ride home, but only like 3 or 4 times out of the 30 times i probably hit the brakes.

so i get out of the truck expecting my fluid to be really low or a leak somewhere, but i see nothing in relation to a leak, check the fluid and its good. so now im thinking, could air have gotten into the lines? or do i need a new master cylinder or brake booster?

just looking for some help, plan on bleeding the lines and seeing if that solves my problem, then if that is not it getting a master cylinder or a rebuild kit if they make one.

thook

I'm going to guess the master cylinder has blown. The inner seal, that is. If you'd blown a line or wheel cylinder, you would have lost fluid noticeably as much as you said you've hit the brakes.

Try pumping the brakes to a point where they will hold. Hold the pedal, and if it creeps slowly down that would be a master cylinder problem.

91TPU

i can pump them up a bit and then the minute i put any stopping pressure on the pedal it sinks into the floor. i still have braking power, but the pedal is on the floor. Do they make a rebuild kit? or just replace it? and with that will it get worse, like no brakes at all or is this as bad as it will get. We are having some bad weather and i need a 4x4 vehicle.

zlathim

T-hook is right as usual. Your master cylinder is bypassing internally. You won't find any leaks, and it is somewhat intermittent, at first.

Just buy a remanufactured m/c, bench bleed it (the good ones include the bench bleed kit with the m/c), and install it. Shouldn't take more than an hour to do start to finish.

91TPU

would i be better off getting a remanufactured or just getting a rebuild kit. this is not my daily driver, and i can afford to have it off the road for a day. im pretty mechanically inclined, but honestly i have never rebuilt a master cylinder. i see a kit from raybestos online for like 45 bucks, most new a reman mc's are between 50 and 175. i dont mind spending the money, im just trying to find out what my best plan of attack is.

thook

You're best off getting an Aisin master cylinder. But, to save a buck, the next best is get one with a lifetime warranty from NAPA or O'Reilly. I don't care for Auto Zone brake components. But, that's just me.

I say that because after you've spent the money and taken the time to rebuild it, if it leaks or fails you're in the same boat, again.

91TPU

thats exactly my thoughts. i went searching and found an aisin one http://www.autopartswarehouse.com/de...3-1614735.html
i think thats what im going to go with. i also see wabbit has one that is bigger? aisin one says its 13/16ths and wabbits is 1 inch.

this being wabbits http://www.wabfab.org/products/brakes/brakes.htm

both pretty much the same in price, what do you guys think. id love to give my money to wabbit as it supports him, but if the aisin is a better fit and better unit itself i would stick with that. what do you think.

ps thanks for the help thook i havent really done much brake wise other then calipers rotors pads and bleeding, never really done any master cylinder work or brake booster work so its all new to me.

Ezrider_92356

i rebuilt the master on my Toyota quite a few years ago and still working great, very simple do to, the only slightly uncommon tool you need is a set of snap ring pliers

thook

Aisin, Wabfab, or even rebuilding your original.....it's all good stuff. Just depends on what you'd prefer. Weigh the pro's and con's.

Personally, I like Aisin (even a good rebuild) because they're dependable components. It doesn't have a cylinder as large as Brian's (Wabfab) and therefore not as much hydraulic capacity, but it's been fine for my daily driver what with frequent hauling and towing. The draw back was the price and a limited warranty. (But, it's an Aisin.... it will last for YEARS!) I'm sure Brian's is just as reliable. He wouldn't sell junk, and he's a stand up vendor....meaing, he'll take care of you. But, his unit is targeted more for heavy duty offroad. Doesn't mean it wouldn't work for average situations, though.

Anyway, Ezrider makes a good point. So, why don't you have a look at your original one before deciding? If it is an Aisin and in decent rebuildable shape.....ie. no pitting or scoring (otherwise, a reman w/LT warrany is the better option)....you could save some money for now and it would be a good learning experience to rebuild it. True, you wouldn't have the warranty, but still......learning is also a good thing.

I'd have probably rebuilt my original from a long time ago, except the PO had not maintained the brake system well. It was pretty much toast and would've more trouble than it was worth..... even though it was an Aisin.

91TPU

cool, thanks for all the info, its very much appreciated. i think what im going to do is pick up with brians or the aisin, not sure yet as the truck will see a lot of offroading. im also going to pick up a rebuild kit as well. rebuild the one i have, and either sell it off or keep it as a spare, not that i think ill ever need it but who knows. plus ill get some experience.

thook

Hell, I'd atleast keep it as a spare. Spare parts are a very convenient thing to have. Just don't let it rust up. Spray it liberally with some silicone spray (not a penetrant!<<<degrades the rubber over time) and keep it in a ziplock.

And, you're welcome.....

91TPU

so i went searching locally, found a rebuilt aisin. was the best price. gotta give my old one back for the core, but thats ok. honestly i wanted to buy brians, but hours have been scarce at work and i promised a buddy i would help move next week, and another buddy asked for help today so i just went and picked up the rebuilt. gonna go get wrenching now.

thook

Stupendous. Good luck and post back the results, if you would. And, if your truck blow up, it's zlathim's fault......>>>>runs in haste>>>>>

91TPU

so everything went very well, besides it being sub freezing outside when i did the work. all the lines came off good, unbolted the master, transfered over the resevoir and put everything back together. it was no doubt a needed fix as my pedal is now back to where it was. did not bench bleed however, just didnt have a vice handy(we moved 2 years ago and still have not found it) so i just bled it on the truck. brakes are slightly spongy compared to how they used to be, but as soon as i get some good weather i plan on gravity bleeding everything so no worries on that(really wanna get some new, clean brake fluid in as the old stuff is practically black).

all in all everything went very well, again i appreciate all the help and encouraging words.
now on to the next task, upper rad hose and thermostat.

thook

You reused your brake fluid? I understand if you did what you had to do under your circumstances, but do change that out ASAP.

If you think you still have in the master cylinder, you'll need to bench bleed it, again. On the vehicle works. But, your spongey pedal could just be the old fluid. That'll happen.

Don't forget to bleed the proportioning valve, too.

Otherwise, I'm glad it went well. Brakes can be a pain.

91TPU

no no, i didnt reuse the fluid sorry i didnt make sense. i drained and cleaned the resevior(and when i say cleaned i mean i am super weird about putting dirty things back on the truck, i swear it looked brand new when i put it back on lol), but i had to swap my current resi over to the new master because the replacement didnt come with one. i tried for the life of me to get one with it, but i only found one master out of the 14 stores i called or went to after work today. i replaced all the fluid that was in the resi with new synthetic DOT3, and once the weather gets warmer, i plan to bleed all the brakes themselves, for now i only bled the master cylinder. i just meant i wish i could have flushed the lines clear of all the old fluid by bleeding everything, but its far too cold for that today and i dont have a garage to work in

i plan on doing a 4 wheel brake job in the next few months, so when i do the brakes i plan on gravity bleeding all 4 and the prop valve and flushing all the old fluid out for new stuff.

thook

Ah. I see. Lol.....thanks for clarifying. Yeah, I don't have a garage, either. So, I can completely relate.