84 Toyota brake issues

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Bain

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I did search and couldn't find much info.. I have a 84 22R 5 speed. When I got the truck the brake pedal would pump with the truck off but when I cranked it the pedal would go to the floor and wouldn't build pressure. So I checked all the lines and installed a new master cylinder (bench bled) and it still has the same problem..I thought when a brake booster went out the pedal would get stiff ( like when the trucks off and not getting vacuum). and there's no air in the lines..Whats the odds of me getting ANOTHER faulty MC or could it be the booster? Thanks
 
When you bled the system after installing the new master cyl, did you bleed the proportioning valve first, then rr, lr rf lf?
 
It sounds like your MC is leaking internally past the seals. You are correct about the booster not being it.
 
adjust the rear brake shoes ? have you done this, or at least checked them ?

the LSPV modulates fluid front and rear, if the shoes aren't adjusted right, you may not get a pedal, or a weak one.

also, verify what calipers you have up front, is this a completely stock truck ? or has someone installed vented Cruiser rotors and V6 calipers ? if the rotors and calipers have been changed, you may need to swap in a different master cyl. Stock rotors are solid/non vented
 
Ive had this truck a few weeks and Im not sure what alls been done to it. But its been lifted, locked, geared and a few other mods..Just checked and the front rotors ARE vented..and heres a pic of the caliper..not sure how to tell if its a V6 or not...

252478_10150283545660482_665190481_9498354_104845_n.jpg
 
Are the pistons on the calipers the same size or is one bigger? If they're the same size, you need a bigger bore master cylinder. I'm running the ones with different sized pistons and don't have any problems with my stock MC.
 
x2 on LSPV, I think you can bypass it pretty easily, it can definitely screw with your braking
 
They are different sizes...It will be Monday before I get a chance to mess with them again...
 
Rear disks or drums?
 
Gotta be an internal leak in the MC.

Or maybe a rubber line that's soft and just expanding all the volume of the MC?
 
well..put in ANOTHER master cylinder..new wheel cylinders and brake shoes and adjusted the brakes and still no pedal :confused: should I be able to hear a little suction sound coming from the LSVP?
 
Toyota

Have had this same problem
Gravity Bleed all wheels----- (One at a time Rears 1st)
Yes it will take a while
DONT let Master cly Run out
then hopefuly You should have some Pedal
Then Bleed Normally
 
just gravity bled them and still have no pedal..Cant get help bleeding them til monday..I pulled the vacuum line off the intake that goes to the booster and the pedal got stiffer and the truck died..so its getting vacuum..
 
I worked on bleeding the brakes some more this morning..now the truck will actually stop..but brakes still suck. with truck running= i hit the brakes the first time and it goes to the floor and I hear the front calipers slap the rotor..hit them a second time and I have better brakes...so at least they are pumping now.. The booster IS working and so is the check valve..It almost feels like I have V6 calipers and not enough pressure to work them or not enough stroke in the booster..I'm just trying to eliminate things before I have to wrestle with changing the booster..

262339_10150293080275482_665190481_9596285_6632024_n.jpg
 
That is really strange. It just doesn't seem like a bad booster would cause those symptoms. Guess it's just one of those things.
 
rattlecanpaint said:
That is really strange. It just doesn't seem like a bad booster would cause those symptoms. Guess it's just one of those things.
Click to expand...
Thats why I was so hesitant to change it...but everything else was new so I figured what the hell.. :)
 
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