90 V6 4Runner.
New master, rotors, pads, shoes have put 3 different boosters in (latest one brand new) several gallons of fluid bled through system and still no brakes no leaks, no swelling lines, everything bleeds out smoothly. Still failing booster pedal test...makes me think it must be a vacuum leak at this point. Anybody know what the vacuum should read at the booster vac line? Check valve good. Rubber vac line good.
There is also a terrible idle when warm issue I haven't been able to solve. Replaced coolant temp sensor. I'm out of ideas and after throwing several hundred dollars at the truck I'm just hoping a vacuum leak will kill these 2 birds with one stone.

 

did you replace the whole booster unit or the master cylinder(the part that has the fluid resivoir, that connects to break pedal?)
i don't know the what the vacuum numbers should be

have you tried using carb cleaner or starting fluid to see if you have a vacuum leak?
spray it around your motor and it'll idle up when you spray over the leak

 

Thanks for the quick reply.
Both the master and the booster.
Here is a link to my other thread regarding the idle issue and some things I've been trying to find vacuum issues.

https://www.yotatech.com/forums/f116...n-warm-185266/

 

ok, i checked it out. i don't really know much about these 3.0 motors. my guesss is like you said something about your TPS is throwing a code, which makes me think a vacuum leak leading to more air tripping the TPS a little. i'd just try some carb cleaner or some starting fluid because that mapp gas can get blown aroun by the fan.

ok one more thing, you might think i'm some crazy dumba$$ that thinks i know more than i really do but, my little brother had a '93 pickup that my dad bought brand spankin new in '93 with the 3.0. it was a great truck, great motor. but around 170,000 it started having a real rough idle and get a little warmer than usual. call me friggin crazy but we replaced the thermostat and it ran perfect. no joke man. i'm not playin around at all. just wanted to throw that out there.

 

but that doesn't really pertain to your brakes, sorry. man, i don't really know what else to tell you. not to sound like a know it all, but you sure your bleedin them properly? like an extra person to help you, to pump and hold the breaks? and your sure your keepin an eye on the fluid level in the res? making sure to close the bleeder vavle before the fluid gets back to the valve? sorry man, this would frustrate the heck out me too

 

Thanks again. T stat is brand new. I've got under 500 miles on the thing since I did the valve job/head gasket. I also had the injectors blueprinted at that time.
I have an 05 Jeep Liberty with a V6 and 00 Lexus RX300 V6. I'm thinking of testing vacuum on both these vehicles at the booster vac line to see if I'm in the ball park.
The rough idle and braking problem slowly came into play at the same time after doing the rebuild and driving smoothly with no problems for a couple hundred miles.
Thanks to all who are checking into this and I'll post updates/findings.

 

good luck man, hope you get it figured out.

 

I have an old vacuum gauge that reads inches...both the 4Runner and Jeep are reading between 13 and 14 on this gauge at the booster vacuum lines.
Does this rule out a vacuum leak? Or at least the idea that there's not enough vacuum to make the booster actually work?

Another thing I just noticed is that the idle is raising when I push the brake pedal.

 

i suppose so man.

you sure there no leaks in the break lines? like 100% sure?

after you bleed the brakes, does the pedal hold? or does it go straight to the floor?
are you bleeding them when the vehicles running? i've always done it with it off, don't know it makes a difference or not but just throwin it out there

 

hey one more thought, do you think it could be the load sensing poportioning valve on the rear axle? i hear alot times they get stuck open and draw alot of air in, how long was the motor out of the vehicle? maybe with out the wight up front it caused it to open and now its stuck open?

 

What exactly is the brake problem? Does the pedal sink to the floor? Is it like a rock, no booster assist? Does it pull,shake,vibrate? You don't say.

 

Theres a method to bleed the brakes, by the way.
You cant just go in any plain old order.
Gotta go drivers rear, Passenger rear, LSPV, i think passengers front then drivers front..

Gotta go longest to shortest in terms in brake line length.

 

definitly sounds like the vacum line coming off the booster is leaking... have you checked that one really well? if that was leaking it would give you a bad idle and bad breaks... just an idea.

 

hi,
Need more info on brake pedal feel. Based on info you provided about the parts that were changed. The booster has a push rod that must be adjusted before it is installed. The master cylinder needs bench bleeding prior to installation. After these procedures, Start by checking for hydraulic pressure at the master cylinder and brake assemblies. Let me know what happens and so we can narrow your problem down to a simple solution for example (improper adjustments, clogged line etc.)
Good Luck

 

Thelast83inNJ=Pedal does not sink to the floor, pull, shake or vibrate. I mash the brake pedal and the truck gradually rolls to a stop. It fails the booster pedal test, where you hold your foot on the brake, start the truck and pedal should drop; pedal does not drop. Booster is new and holds vacuum.
peow130=The system has been bled in the proper order; Drivers Rear, Passenger Rear, Passenger Front, Drivers Front, then LSPBV.
YellowTT= Push rod is within specs on the distance allowed, master cylinder was bench bled. All the lines bleed out fine, no clogging, swelling...
The vacuum at the end of the line where it hooks to the booster is the same as it is everywhere else, so I think that line is good.
Thanks for your responses. Anybody have a gauge to hook up to theirs at that point to compare?

 

no gauge or I would for you. Come on down the hill and bring your gauge and I'll test mine.? If you have brake issues though probably not the best idea.

 

Alright, here's what I'll go with. You have a good brake pedal. If you have been driving this truck repeatedly testing the brakes, maybe you have overheated or glazed the pads and shoes to the point that the truck just skates and doesn't stop quickly or the way it used to. [Stopping like a mad truck driver]. Maybe the pads and shoes need to be sanded and scuf/machine the rotors and drums. Maybe different set of pads? Different compound? I'm 3,000+ miles away or I'd take a ride in it.

 

FYI
Your engine vacuum reading should be around 18-20 inches/Hg if everything with your rig is mechanically sound. Your reading of 14inches sounds pretty low.

 

Hmm...this gauge reads mm/hg. I'll pick up a new gauge.
Thanks.
Pads and rotors are brand new. I drive 10 ft out the driveway every time I test something and see that it's not going to stop and I back it back in. Rotors and pads have 0 miles on them.
I live in the mountains and if I even get on my street I have to take some very steep hills. I can't Really go anywhere, it makes this a lot harder to deal with!

 

You are only a couple of inches of vacuum off, which probally is your idle problem. But you should have some assist. You said you didn't have any problems bleeding, so no restrictions throughout. Man, I don't know without driving it. You got me, but I want to to know.