# Brake help please



## minitrkingking (May 10, 2009)

I changed out the rotors and pads on the 86 720 and cleaned everything up. Everything is back together and fitting fine but the brakes aren't bleeding. I followed the instructions on wiki to keep the cap on, depress pedal, open valve and close, let pedal come up? RIGHT??? Started at the passenger rear then driver and the same for the front. What am I doing wrong, these brakes have me pissed off


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## minitrkingking (May 10, 2009)

We continued to bleed as stated above and we get pressure when the truck is not running (it has pressure on the first push, doesn't need to build) when the truck is turned on the pressure is gone and has to be pumped to build up. The brake indicator is on and off flickering.


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## zanegrey (Dec 5, 2005)

why did you bleed the system if you just changed brakes an rotor ?

i am having a similar problem with my 87 so i have determined the the rear wheel cylinder is shot..

check to make sure that you do not have a purportional valve that must be bled...


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## minitrkingking (May 10, 2009)

We disassembled all the brake parts, cleaned and painted them. While the brake lines were hanging all the fluid emptied so now we're trying to start from scratch I guess?


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## zanegrey (Dec 5, 2005)

check to make sure that you do not have a purportional valve that must be bled..

when bleeding the brakes .
do it with the engine off.

fill res..

have some one pump the brakes and hold.

u open the bleeder to expel air then close..

then have the helper release and re pump..

do this three times on each wheel..


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## minitrkingking (May 10, 2009)

Thanks, we have been doing that exactly. Gone around the whole truck 3 times since yesterday. Before we started, the brake light would come on and stay on while pushing the brakes, now we turn on the truck and it flickers. Could the brake master be bad even though it worked before we started? Thanks again for the help


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## brookwood61 (Aug 18, 2005)

If I remember right, there is a valve like Zane mentions, in front of the gas tank, up in the frame. There is a line going to the rear brakes. Bleed that, too. I'ld go out and look under mine, but it's sitting in slush right now.
Good Luck


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## minitrkingking (May 10, 2009)

That sounds about right, I just need to locate that valve. Thanks! the truck has been sitting for 3 days because of this.


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## Grug (Aug 20, 2009)

The proportional valve on my '93 2WD was over the rear axle. I once had a bad line going into the valve. Thought maybe it was the actual unit itself so I priced one out. Wowsers, you know what one of those valves goes for?? It was about $400.00 (and that's not at Nissan either). Was glad it was the line going into the valve!

Sounds like you pretty much emptied the system of fluid and filled it with air which means you have a lot of bleeding to do.


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## minitrkingking (May 10, 2009)

I bled each wheel until nothing but clear fluid came through with no bubbles then pumped about 10 more times per wheel. It rained today so I'll look for the valve tomorrow.


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## zanegrey (Dec 5, 2005)

maybe bleed it up by the mc...


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## minitrkingking (May 10, 2009)

Tried again yesterday with no success. Did not find any rear valve but I found a splitter block and attempted to bleed from there, also near the master, no bubbles or air at all and still barely any brakes. I'm taking it sometime this week to a mechanic.


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## zanegrey (Dec 5, 2005)

get ready for an 800 dollar bill..

the first thing they will do is mic the rotors and drums and ofcoarse they will be out or so close that you might as well replace them..
then they will try to scare you by saying if the do not replace the mc.wc and calipers they cannot gaurantee the job..
then there is the breakage that will happen because the truck is 20 plus yo..

i know you have to have brakes but get ready..


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## minitrkingking (May 10, 2009)

I just put new rotors, pads and caliper hardware on. I have the two stainless lines that are being made this week. The shop is less than a mile from me and the guy is honest from my experience. My plan is to have them bleed the brakes for me and see if things change, if they come up with another diagnoses I will do the work myself. Hopefully things work out. If the master is toast I may use this as an opportunity to replace it with a smaller setup and run all new lines but I'd rather it just work. I had an astro master in my s10, anyone know what the equivilant would be for the 720? Thanks as always zane you are the man!


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## minitrkingking (May 10, 2009)

I had someone look at the truck and help bleed the system. They pulled the hose from the brake booster and we instantly gained brake pressure. We bled at the wheels and at the master itself. Does that test tell me if I have a booster problem?


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## zanegrey (Dec 5, 2005)

i do not think so..

all you are doing is removing the vacumn assists..

did it fix the brake problem??


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## minitrkingking (May 10, 2009)

It just made the brakes manual. I drove it to the store about 2 miles away and it had pressure in the pedal, it still needed pumping to actually stop. With the vacuum hooked up it just goes to the floor with little pressure and then the brakes lock up.


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## CMax03 (Jan 17, 2009)

Bleed entire system! Find bad caliper and if still going to floor after caliper is fixed M/C is shot!


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## minitrkingking (May 10, 2009)

I am soooooo open to suggestions on these brakes. With no question, the brakes have been bled properly so maybe it is the caliper? How would I check to see? Should I take the rotor off and see if the caliper squeezes? I am about to order a used booster and m/c together for 45 bucks just incase. Sucks if it's the caliper because we spent a good day cleaning and painting them. One of the caliper brakets were siezed, the shop fixed it before we put it back in. We have been driving it very lightly with manual brakes the last couple days.


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## zanegrey (Dec 5, 2005)

i have put 5 mc on mine ..
az called the cops on me because they just new i was ripping them off..

i doubt it is either the mc or booster..

there is simply still air in the system..

my fronts bleed correctly but the rears do not..

i think mine is the rear wc but it has been too cold for me to do the work...


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## minitrkingking (May 10, 2009)

Jesus P. Christ!!! I don't know what it is? We drove it a good distance today with no booster line hooked up. It isn't fun but it gets there. I'm so broke that I can only fix one problem at a time but I can't really find this problem.


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## zanegrey (Dec 5, 2005)

i do not know how to respond to that...


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## minitrkingking (May 10, 2009)

no need, hahha I was venting a little there.


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## zanegrey (Dec 5, 2005)

u should hook the vacumn back up..

also i have noticed that driving it has allowed the pedal to pump up more than it does when bleeding it..

so i am thing the air is moving ..so maybe after driving it for a while might make it easier to bleed..


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## tinworm (Aug 20, 2009)

At this point I would use a hand vacuum pump to draw brake fluid down through the system and try and suck out an air pocket. 

Leave the cap off, and top off the master cylinder constantly, there is no point to leaving it on if you are working on it, air can only be introduced if you draw the fluid down enough that air can be sucked in the lines. Much better to maintain a constant level than to pop the cap afterwords and suck in air cause it was so low.

What are you getting for flow when you bleed? If its fully bled, when you have someone put pressure on the pedal, then open the bleeder, you should get a jet of fluid that goes about at least 10-15 inches away, no dribbles or slow flow. 

If you have no obvious leaks (best test is clean it off with brake fluid, then blow it dry with air, then have someone put a lot of pressure on the pedal while you inspect for leaking), there are really only two options. 

1, its not fully bled, and 2, you have internal leakage at the MC or at some proportioning valve. If it was fine before, its probably just a huge air pocket floating around in there, especially if you were painting and finishing with the lines were open. Keep bleeding each wheel until you get a positive jet of fluid each time you open the bleeder. It may take way more than 3 times a wheel.

On heavy trucks, my basic procedure is Right rear, left rear, right rear, left rear, right front, left front, right front, left front, right rear, left rear, right front, left front. 
If the rear uses a splitter, opening the opposite bleeder will require you to go back to the brake you just bled on the same channel. back and forth, back and forth until you have the same flow on both sides. 

This is the full procedure we use with someone helping us. First, with the new hardware installed if we were putting on a new caliper or whatnot, I open the master cylinder, fill it up, and open the caliper bleeder and let it gravity bleed while I complete some other work. When I have a drip, I close the bleeder, check the master level, then have someone pump on the pedal until they have something. Then I call "down" and they put constant pressure on the pedal. I then open the bleeder and release the pressure and they yell "down" when the pedal reaches the floor. I close the bleeder and call "up". They let the pedal return to the up position and yell "up" when its completely up, and we repeat until I have solid flow coming out if the bleeder. 

I follow the same procedure until I have all the air worked out of all the calipers and lines jumping back and forth until I get the same flow everywhere while topping off the master.


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## zanegrey (Dec 5, 2005)

i did try the vacumn pump to no avail..

my fronts bleed out good .
but the rears do not spit..they just kind of drool...

my truck has no ppv...


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## CMax03 (Jan 17, 2009)

It's not bleed correctly if the fronts are only been bled!


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## minitrkingking (May 10, 2009)

Thanks tinworm. I feel that I must have some other problem. The brakes blast fluid nearly 2 feet in the front, I've been hit in the face, it sucks. The rear is more like a steady flow. I have bled each wheel in rotation many times over, at the mc, at the rear splitter which doesn't have a bleeder. I feel really stupid right now. I don't think it's a caliper because it doesn't pull to either side when braking. The brake warning light has stayed off since I capped the vacuum.


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## tinworm (Aug 20, 2009)

Is the bleeder blocked or restrictive, and 2 is there an internal blockage inside the brake part itself that still allows it to work but could be keeping air in there?

How about a collapsed rubber brake line? It would not be obvious from the outside, but could be closed up inside if its delaminated some. You could work your way back piece by piece.

I once had a hydraulic clutch that worked great until I went to replace the clutch and pulled down the tranny. I disconnected the line at the slave, did the job, then when I went back to install and could not bleed the clutch. I found that no fluid would come out even if you completely removed the bleeder from the slave. The orifice was blocked inside the slave itself, but until I opened it, it worked great. 

In other words, everything was fine until I dared to do some other maintenance, then all hell broke loose.


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## Grug (Aug 20, 2009)

Did you have the rear drums off? I quickly looked over previous posts and didn't see any mention of rear drums being off. The only reason I'm asking is that you say the force of the fluid when you bleed the brakes seems to be much stronger at the front. Those rear cylinder bleeders should be spitting out fluid just as strong as the front calipers.

I'm wondering if the rear drums need to be pulled and a close inspection of the rear cylinders done. I know it's more work based on a hunch, but it sounds like you're not getting the same pressure at the front as at the rear.

Make sure the brakes are properly adjusted when you replace the drums.

Like Tinworm said, you've kinda' opended Pandora's Box with the front brake line work and maybe all Hell's broke loose...or at least at the rear cylinders??

By the way, I've always bled my brakes with the engine running...not sure if that's the right thing to do, but it's always worked. Nothing like a face full of exhaust while working on that left rear wheel. But I also like the smell of napalm in the morning.

Good luck, man!


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## zanegrey (Dec 5, 2005)

mine is definately the rears not bleeding..

i get a little spit from the drivers side but just a flow from the passenger side..

this is what makes me think it is that side wc..

but again it is too cold for me to do the work yet..

least we forget i am 67 yo and the cold seems to be worse on me the closer i get to the otherside...


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