Author Topic: scary brakes  (Read 1802 times)

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baldwookie

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scary brakes
« on: Oct 01, 2007, 08:59:14 AM »
hi,
just recently bought this truck... and its had scary brakes sense ive bought it.... knew it needed some work when i bought it... after more closer inspection... i know im gonna replace rotors/calipers/pads  maybe even master cylinder
theres elec tape on the brake lines, im guessing to stop a leak... but what had be stumped is the top line on the lspv.. it isnt there... just had duct tape over it...where is this line suppose to go, could this be loosing all my pedal pressure?  brakes go to the floor then it will dive to the left... my thinking thats the closest to the mc.. why it gets some pressure... any help would be greatly appreciated
1980 lwb sr5  stock

*ROKTOY*

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Re: scary brakes
« Reply #1 on: Oct 01, 2007, 09:47:27 AM »
I would go to how to guides and download the 85 FSM it will answer all your questions.

Oddmar

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Re: scary brakes
« Reply #2 on: Oct 01, 2007, 02:27:16 PM »
Man, i thought Wookies had more experience than this...j/k

Imagine pushing on the brake pedal...this pushes a piston through a cylinder, building pressure which flows through brake line tubing, putting pressure on the pistons in the (slave) cylinders at the wheels, which in turn are supposed to apply enough force to the brake pads/ shoes to STOP THE TRUCK!!

There 'aint no way in Hades that DUCT TAPE and electrical tape can hold back this kind of pressure. Sounds to me like you need to find a master cylinder, replace ALL the brake lines, (brake tubing is pretty cheap), and i'd bypass the LSPV cause it's probably locked up not allowing any pressure to go to the rear brakes anyway (all of ours have been junk so far).

If this causes scary sideslipping on water or ice, install a Wilwood proportioning valve ($40) in the line going to the rear brakes, you can adjust this manually to balance the braking system. People say to put the Wilwood valve next to the master cylinder, but i've found it easier to adjust if it's in the cab...it's easy, it's on the rear line anyway.

If the truck pulls left when the brakes finally work, it means the left front caliper is the only one doing any work. Make sure all four pistons in both calipers are moving freely when you compress them (with a C-clamp) as you're putting in new brake pads. If the pistons are locked up, the brakey no worky. And if it's a straight front axle, the axle/ knuckle seals are probably shot, allowing gear oil/ grease to contaminate the brake pads, which makes them almost useless. If so, you'll need to replace the felt/ metal knuckle seals, and the oil seals inside the axle.

It might sound like i'm advising you to replace EVERYTHING, but i'm not. There's just alot of things in the front end that affect each other, and probably no one has done proper maintenance on these parts since the truck left the factory. The good news is, if you replace it now, and take good care of it, it'll last a looong time. This IS the BRAKING SYSTEM we're talking about, right? Better safe than sorry. Last thing anyone needs is a manslaughter charge cause they ran over someone's little kid.

Feel free to ask more questions if you need to...that's why the forum exists...furrball.
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NT-OUTBACK

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Re: scary brakes
« Reply #3 on: Oct 01, 2007, 03:53:34 PM »
 :wave:

 
« Last Edit: Oct 18, 2007, 10:40:25 PM by NT-OUTBACK »

unclejpl4x4

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Re: scary brakes
« Reply #4 on: Oct 01, 2007, 04:19:12 PM »
:yikes:  they got that bad kevin :yikes:   you doing need no LSPV  cut it out   well bypass it
build thread http://board.marlincrawler.com/index.php?topic=39214.0
CB install http://board.marlincrawler.com/index.php?topic=45467.0
roundeyes http://board.marlincrawler.com/index.php?topic=33294.0;highlight=round+eyes
LC exhaust head 2 tip, EB RVstreethead O/S valves,EB  268c/torker cam , .20 over , metal t-chain wear pads
MARLIN clutch 1200, master clutch cly

baldwookie [OP]

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Re: scary brakes
« Reply #5 on: Oct 01, 2007, 08:47:28 PM »
oh yeah joe they have gotten pretty scary,  thought maybe it was just on the trails, using em a bunch was making em kind of spungy,  but they've gotten worse,   and ya knuckle rebuild is in the near future,  lots of oil leaking on the inside of the wheel,  and out the hubs it looks like... yep next paycheck braided brakelines, and rebuild for knuckles.    maybe even a new mc,  just in case, upgrade to fj rotors/calipers also....wish i had a camera,  where does the top line go to on the lspv anyway,  yeah i think im gonna do away with it.. someday id like to add discs in the back....oh an this wookie has very little if not any experience :).. all i have is a willingness to learn
1980 lwb sr5  stock

blyota91

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Re: scary brakes
« Reply #6 on: Oct 02, 2007, 02:45:31 PM »
When ever I run brake lines to the rear on a yota I'll put tape on one of them so I don't mix up the two lines to the LSPV.
Retiring the 91
Rebuilding the 94

YotaJosh

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Re: scary brakes
« Reply #7 on: Oct 04, 2007, 10:07:31 AM »
It sounds like someone put a LSPV on your truck from a first gen. That loose line you have is the bypass line that routes fluid back to the front brakes in the event of failure.

LSPV's from the 79-83 trucks didn't have this line (at least none of mine did). They just have 2 hard lines: one going in from the frame rail, one going out to the rear axle.

Quoting Roger Brown (http://www.4crawler.com/4x4/4R_suspension.shtml#ProportioningValve):
Quote
The final function of the LSPV-BV is as a Bypass Valve. What that does is to sense the front brake circuit pressure (via the 3rd brake line that runs up the frame rail to the passenger front corner). IF the front brake pressure falls too low, the Bypass Valve basically overrides the proportioning valve and send full brake fluid pressure to the rear brakes to ensure adequate braking in case of front brake loss.

I'd just remove the LSPV, and add an adjustable proportioning valve from Front Range: http://frontrangeoffroadfab.com/nfoscomm/catalog/product_info.php?cPath=27&products_id=57&osCsid=a87fbaea234e762a9a22713d7c486f04

Are you leaking brake fluid from any lines, bleeders, or wheel cylinders? If not, and your brakes are just spongy, I'd flush the system, and gravity bleed it. Don't mash the pedal numerous times to bleed it (like the old "pump and hold" method). It just adds bubbles to the fluid, and will starve the piston in the MC, causing more air. I usually open the bleeder, have someone mash the pedal slowly and hold, and I close the valve, and have them letup. Wait 10 seconds or so, and do it again.

Brake fluid is cheap. Try and get what you have going first if you aren't leaking anywhere. Throwing money at it doesn't always fix it (but the new MC and braided lines sure are nice!).  :twocents:
'79 Short Bed Pickup 4x4
'04 4Runner V8 Sport 4x2

baldwookie [OP]

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Re: scary brakes
« Reply #8 on: Oct 05, 2007, 09:39:43 AM »
thnx josh,  gonna try that this weekend... cant really tell if its brake fluid.. think its fluid from the axle seals.. wish i had a camera id post some pics, another thing tht makes me believe its not brake fluid reservoir doesnt go empty
1980 lwb sr5  stock

unclejpl4x4

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Re: scary brakes
« Reply #9 on: Oct 05, 2007, 03:01:28 PM »
could be a bad seal in the master cly
build thread http://board.marlincrawler.com/index.php?topic=39214.0
CB install http://board.marlincrawler.com/index.php?topic=45467.0
roundeyes http://board.marlincrawler.com/index.php?topic=33294.0;highlight=round+eyes
LC exhaust head 2 tip, EB RVstreethead O/S valves,EB  268c/torker cam , .20 over , metal t-chain wear pads
MARLIN clutch 1200, master clutch cly

 
 
 
 
 

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