brake booster issues (other then air leaks)

This might be what you were looking for.



After looking at this parts explosion, there is quite a bit going on under our dashes.

 

so you think its in the linkages somewhere? it sure does feel to the foot like its a a hydrolic issue

yes there is a lot going on, but im seeing nothing there that, to me any way, makes any sense that it could cause the "random" binding symptoms I have?

what is your opinion, now that you see how the pedal setup works?

 

You could disco the pushrod from the pedal,,then feel for wear in that pedal assy. Fresh everything, rapid in-vehicle bleeding? might have taken something else out. Shattered bushing could cause a weird drag.

 

its just so strange feeling when it does it and then returns to normal again.

good idea disconnecting the bellows, but then I cant seam to get it to repeat the condition when I try to get it to so its very frustrating and my bad eye sight doesn't help when trying to look at thinks and see "something" out of the ordinary.

I guess I don't have much choice other then to tear the whole pedal assembly apart and examine everything??? after 12 years I suppose it wouldnt hurt to replace all those bushings and regrease every thing under there anyway but if I knew what a brake booster looked like internally and how it worked I would feel better about making a decision to replace it without knowing if its bad or not so time to google search that I guess

 

well after looking at the internals of brake boosters there seams to be a whole hell of a lot more stuff going on and a lot more internal parts to it then I ever imagined there was




I will definitely check pedal functions every which way but I think getting another booster is in my future

 

well I pulled the booster connection loose and the pedal is free and easy but I still pulled all the pedals apart and everything is fine there, no worn bushings or anything wearing, binding, or loose.

so I ordered another booster from car-parts.com

wasn't bad on price at all, only $25 plus $15 shipping = $40 total

guy said they were that cheap because they almost never sell any

 

UPDATE:

replaced the booster and its all good now, it moves easy and smooth all the way now

before, when I "thought" it was in its periods when it was working normally, it would stiffen up and offer slight resistance after about an inch of soft pedal and I thought that was normal and just where the pedal pressure was building to apply more pressure to the brakes, but now that that's not there anymore, I realize that wasn't supposed to stiffen like that and now its smooth all the way from full up to fully depressed and brakes are working great.

removal note 1 - I didn't have to disconnect the brake lines from the master cylinder, I just removed the vacuum hose, then the two nuts holding master cylinder and dont lose the check valve holding bracket, now take the brake light wire off and remove the snap in keeper from fender so it gets completely out of the way, then unhook the fuel line, master cylinder from booster, and gently pulled the master cylinder forward enough to allow the booster to come out. there wasn't a lot of clearance and it took a little wiggling and finagling but it comes out without having to remove master cylinder and bleed your brakes.

removal note 2 - under dash was a real PITA until I figured out you need to remove lower dash and the side door a/c vent duct under steering column to get access to the bolts and pull the yoke catch pin. remove catch pin and top nuts first, then bottom nuts.

to reinstall - start both bottom nuts until snug, then put in the catch pin and clip slightly pushing pedal to align holes, then top nuts go in and tighten those first before tightening bottom ones. then go under hood to finish everything under there.

 

Sometimes, it stares you right in the face. It's good to diagnose a bit, before you just go for the gusto and fling money. That way,,a person learns a bit more.

I would bet that your bleeding process strained/stretched it to max and it gave up. Just a guess.

 

no, this happened out of the blue and only "then" with the brakes acting up, did I replace the master cylinder. I did that for two reasons, 1 I never heard of a brake booster going bad for any reason other then vacuum leaks, and 2 it was cheaper solution and less involved then replacing the booster.

after watching a guy open a booster to rebuild one I saw the insides of the can are just raw unpainted metal and he mentioned it will often collect moisture in it and build up "rust dust" that collects in the bottom and wears on the diaphrams and can cause them to bind. I think this might be what was happening on mine. I shook it after removing it and I can hear "something" in there in the old one so im betting that was the problem and it also explains the come and go randomness of the binding.

but I know what you are saying, an old part can go bad by making it articulate fully after it has been in place for years only functioning in a limited range of movement. most times this is where people find master cylinders leak after pushing the pedal all the way to the floor when bleeding brakes after repairs. leaks happen where rust has formed on the shafts in places where it hasn't extended that far since new and it tears the seals causing it to leak

now having done it, the booster was more expensive, but easier to replace then the master cylinder because there is no need to bleed all 4 wheels

 

FOLLOW UP:

well after a few weeks of working great the booster I got from the salvage yard is acting up as well and has started to also give a "hard" pedal every now and then so trying to save money on salvaged parts wasn't that good of an idea after all and $50 down the drain.

so I just ordered a new booster for $150 and would suggest others learn from my mistake and not try using a salvaged booster.

I learned on youtube where a guy cut one open, they don't paint the insides of the boosters, so they all get rusty inside and over time, this rust falls off and builds up in the bottom of the boosters and jams the movement causing the random hard pedal issues I have.

 

I just read the first couple of post and "yes" boosters can go bad!!! Back when I was in Vo-Tech school taking mech-II in 1983, I had a booster that would try to slam you into the windshield, we didn't use seat belts then. Put a new booster on and it was back to normal.

 

Some Tannerite is in order. Damn junkman!,,he gotcha!. Picked up a used 5 speed for my old rust corrolla,,dude swore it was a 5 speed,,got it hope, put it in,,nope 4 speed. MFMFMF!. Got my cash back,,after I had already pressure washed the thing and ran bolts thru.

Hope the new booster solves your issues. They are listed as a consumable in the Toyota policy fine print. Necessary evil,,it has to be in place for a daily.

 

well a further update is in order

due to limited time issues, I knew I was going to be a week or two before I was able to get around to replacing the junk yard booster that was starting to bind at times, so I pulled the check valve out and squirted about an ounce of motor oil inside the booster (5 or 6 good squirts from a pump lever style oil can). my reasoning is, since its a buildup of powdered rust flakes that cause the binding, I figured the oil might keep it from clumping or maybe turn it into a mud like sludge that would be pushed aside harmlessly to not cause any more binding.

well after adding the oil into it, i had a couple more times it was binding the first day or so and then after that it has never had anymore binding issues so im going to return the new booster I bought and see how long the junk yard one lasts without anymore problems. if im lucky the dust/mud/oil mixture has done what I hoped and its been pushed up out of the way somewhere so it wont be an issue anymore.

it has been 25 days since I added the oil and without any more binding issues so im going to be hopefully optimistic and call it problem solved and fixed by squirting an ounce of oil into the booster.

just a little FYI that its worth trying to see if it might work for your situation before you drop $200 on buying a new booster

now an important thing to note in all of this is that all this is just speculation of whats going on inside my booster as well as what "might" be going on if the rust dust was wet with oil. plus I could hear the rust dust inside my old booster as I shook it after removing it.

after seeing a youtube video showing a brake booster being opened up and how the inner drum is literally within a feeler gauge distance of touching the outer drum and the fact that the video pointed out "and showed" almost all old boosters have an accumulation of rust dust in the bottom that over time can and sometimes do cause the inner drum to jam when it moves causing a hard pedal but still get full normal braking power if stepped on.

 

Check everything again before spending time & money on a booster.

I suspect pumping the pedal rapidly may have induced air bubbles into the system. I also picked up a tip on how to reset the brake proportioning valve. (On older cars) Not sure it works with ABS.
Symptoms: Only front or rear brakes work.
To fix: #1 Open the bleeders on the brakes that aren't working.
#2. STOMP on the brake pedal HARD. This will reset the shuttle.
#3. Close the bleeders and bleed brakes.

 

thanks for the tip, but all the brakes work fine even when the pedal is hard, after thoroughly checking out every possibility, I determined that it was losing the vacuum assist part of the booster.

I "presume" because the inner drum of the boster is getting jammed and not fully articulating as it should is what is going on. I have ruled out any other possibility and replacing the booster solved the problem for a few weeks before I had a few more instances of the junk yard replacement booster doing it too which was resolved by squirting oil into it