brake booster issues (other then air leaks)

im having issues with my brakes

I have all new brakes all around front and back about 6 months ago and in the last month my brake pedal has been acting up. its sometimes hard to press and brakes instantly with just 1/4" of pedal movement and if I literally stand on the pedal it gives way like pressure was forced to release and then is back to a normal travel of about an inch of pedal before it starts to brake.

in all these situations the truck still is stopping just fine but it seams the issue has something to do with the brake booster since replacing the master cylinder has made no difference in the problem.

the pedal moves easily for 7-8 stops then at random its hard like its not getting boost assist

there are no fluid leaks or fluid loss and the booster and check valve has no vacuum leak because I forgot to disconnect the hose and the booster held vacuum for a good 30 minutes after the engine was off because when I replaced the master cylinder it still had vacuum suction on it.

is this a bad brake booster even though its not leaking? I remember when I was pumping the pedal fast to build pressure to bleed the brake lines it was "grunting" under the dash as I pumped the pedal rapidly fast to quickly bleed the master cylinder and build some line pressure, but it doesn't make that noise when its used in a normal pumping action

 

hmmm, no replies yet

cant say im shocked though, I mean I never heard of anyone having a bad brake booster and the few rare cases I read about were having vacuum leaks to be obviously bad ones.

just hat to spend nearly $200 on one just on an "assumption" that that's it but I don't know what else it "could" be?????????????

sure would be nice if someone with experience could help me diagnose it to be sure of what is going on and if replacing it is the right thing to do

 

on a side note - does anyone know

do all year first gen tacos use the same brake boosters?

did they ever change them?

can I get a brake booster from any year and it will fit and work?

 

Sounds like classic vacuum brake-assist failure.
If your vacuum line and check valve are good, another (unlikely) possibility is something interfering with / maintaining pressure on the brake pedal. Check your brake-light switch or the brake-pedal rod-adjuster for anything loose or out of adjustment.
Otherwise, you may just need a new booster.
You didn't state your Tacoma's year or equipment. You might give your specs to a local autoparts store. Then ask what other years/versions their part fits.

Happy Motoring, Mark

 

I already checked the linkages and nothing seams excessively lose or having any type of connectivity or articulation issues but I suppose there "could" be worn bushings or something at the pivot points but I never took it all apart to check those (if it even has anything like that). the truck is in great shape and interior is like new and very well kept so things aren't rusty inside or under the hood

what is going on inside those things that fails on them besides the most common and obvious diaphram leak failure that's easy to detect

what is your background with this stuff? and how often or rare do boosters actually fail with anything other then with leaking diaphrams? in other words is buying a used one assuming they almost never go bad, a good idea

 

All first gen tacos share the same brake booster. The exception being the tacos with ABS. Even then, all first gen tacos with ABS share the same brake boosters with other first gens that have ABS.

 

Definitely doesn't seem to be many posts about them going out. I had one fail on an old 76 Land Cruiser and that's all my experience with brake boosters entails.
Here is an image of the on vehicle inspection process from the FSM for a 2000 taco. I imagine that it's the same for all first gens, being that they share the same booster.

 

Negative. 95-00 tacos have a dual diaphragm booster with a 1" master cylinder, similar setup to a T100. 01-04 models have a single diaphragm booster with a 13/16" MC. The MC and booster are not interchangeable between the two setups, you either need both from one era or both from the other.
The inspection procedure for the booster posted above is the same for all power boosters of all types.

 

thanks, that's very good info

 

brand new ones go for well over $200 and reconditioned ones go for around $175 but used ones on car-parts are going for as little as $25-$35 average plus shipping (I guess they are cheap maybe because its never something people need to change) so i'll try the for sale section and watch for one

at least it is still "working" for now (albeit with issues) but I don't use the truck much and can have other transportation I can use so its not a "dire" need have to fix it today situation

 

just like the above test, all I can find on them is testing the diaphragm for leaks, nothing is ever discussed about how to test the slide or rod movement operation inside them.

the way its acting is seaming to suggest the rod in the diaphragm is getting hung up somehow or its a bad check valve that might seal from leaking down but randomly sticks and doesn't always open again to allow more vacuum when needed because it doesn't leak but it sometimes randomly acts like there is no vacuum assist to it but after standing on the pedal to force the diaphram to move, it forces the check valve to open and allow vacuum in again. but its pure uneducated assumption and wild guessing on my part trying to decipher the symptoms im feeling.

I took the check valve out and its as shiny and clean looking as if it were brand new and shows no signs of sticking or not easily opening and closing as need by blowing on the hose but I sprayed it real good with wd40 just to be safe.

the trouble is, buying the new the check valve, that I have nothing to indicate is bad other then my assumptions it must be the cause and it costs $45, or I can buy the whole booster "used" from salvage yard that comes with the check valve for that same money, but then its good condition but still old salvaged parts.

I would hate to buy a new check valve only to find out I still need a booster for it anyway, so im chasing my tail here going in circles not knowing for sure whats bad on it.

where is that crazy electrode lady at? this sounds like a problem for lovemytacolots, are you out there ???? I bet she could figure this out, she knows how to fix everything there is about these trucks now

 

Interesting. The part number for the brake booster showed the same through all years. I'll double check, not sure what happened. I obviously looked up something wrong. Sorry for the incorrect info. Will correct later with right info.

 

My only bad experience w/ a booster was the check failing and not letting the brakes 'release' after application.

They would just get tighter and tighter after each brake app. 'til the vehicle couldn't move any more.

 

I really kind of think there is something mechanical causing the binding.

On my present '04, the accident had actually pushed the booster down. The point that the booster was mounted to the firewall was bent. I had to hook my chain falls to the booster/MC with a strap and winch it up to bend it to its normal position, thus straitening the firewall.. After that, the MC still needed replaced, but the booster seems to be working fine.

Any chance that the booster is out of alignment? Can you compare it to another Tacoma?

Pretty slick trick posting this thread to Jens' thread. I like it. I'll remember this when I need some help.

 

Vacuum gauge?. You say it held for 1/2 hr?. What does it read idling?

Any witness marks on moving parts?.

 

I don't have those tools, I have no way to measure it but the brakes work normally 95% of the time, its just once and a while it feels like there is no brake assist or like the pedal is stuck but I have braking power what I would describe as feeling like its 80% of what it should be and stopping with just 1/4" pedal movement. in its normal working state it travels about an inch to feel some breaking then about another half inch to full brakes

there seams to be no abnormal movement in the pedal pivot points and I see nothing binding or even like it could bind. the pivot points still have what looks like factory aged grease on them that is still good

when I stand on the brakes when its in this "hard" state, I feels like im forcing pressure relief to go off in the braking system to let the pedal release and then everything is normal for a day or two or something like 20 uses of the brake pedal

I should add, the truck had no issues and was working perfect for a little over a year now and then this just started out of the blue

 

is there any bushings I can change somewhere? I wasn't going to take the pedals apart unless I needed to but it seams to all work smoothly by hand while im under there

 

I found this image, maybe you can get something from it.



This is for a 2004 Tacoma.

 

Here is another.

 

thanks "k" but I was talking about the physical brake pedal under the dash and if there were any bushings on the pins that it pivots on in order to push on the bellows