# No Brakes pumping up



## KrAzY (Sep 29, 2010)

Hello everyone i have a 92 nissan HB pickup with i believe the ka24e ( the 2.4l 4cyl )

i had some issues with the front calipers dragging due to rust and age and decided to replace them, Then the problems started : /

After replacing the calipers and bleeding the lines i still have no brakes the peddle goes to the floor until ya pump it 5-10 times then ya get "some" pressure on the peddle but doesn't hold it and if ya release it and wait a few seconds then press it again it goes to the floor again. It isn't holding any pressure.

So i was told it was the MC that was bad and not holding the pressure so i put in a new MC still to only have the same problem no pressure holding on the peddle when pumped and no brakes, I then was told the resevour was possibly leaking air due to bad seal on cap or whatnot so now i have replaced MC and resevour,filter + cap. And STILL no change in brake pressure. I have bleed the lines 100 times now and there is nothing but fluid coming out at the MC lines and the calipers yet peddle isn't holding pressure and still goes to the floor and doesn't build up any pressure.

Also upon removing the vacuum line off the booster after engine running for a bit and then shut off air comes out of it for a second or 2. I was under the impression there isn't suppost to be any air pressure in the booster because it is under vacuum? So when engine is running the vacuum line is sucking air from the booster not putting air into it so when ya shut off engine and remove the hose there shouldn't be any air coming out of it should there? Or am i wrong and this is how it is suppost to be ?

Also if engine is running and you pump the brakes a bunch of times it will stall out the truck i dunno if this is normal or not. 

All i know is it has got me baffled, And any help would be appreciated.


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## zanegrey (Dec 5, 2005)

sounds like you did not properly adjust the mc input rod...


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## jdg (Aug 27, 2009)

Bleed all 4 brakes, not just the front ones. If you emptied out the master cylinder because the front brakes went to shit and/or swapped out the master cylinder, you probably introduced air into the rear brakes too.
The brake booster holds a "vacuum" provided by the engine. Not pressure. And should hold that "vacuum" after you shut the engine off, I'd say at least overnight. If it's not holding a good vacuum, likely the check valve on the vacuum line (if installed) is bad. If you hear a distinct hissing with the engine running and it's coming from the booster, the booster is likely bad.

You seem to be getting "told" a lot of things...a lot of misinformation. As was stated last year (http://www.nissanforums.com/hb-truck/162845-valve-lifter-tapping.html), stop listening to your friends 'cause apparently they are, for the most part, idiots. I'd bet if you got a Haynes manual or something similar (FSM?), you'd get a lot better troubleshooting and maintenance information. Figuring out brake problems isn't rocket science or brain surgery.

EDIT: Or adjust the rod as stated above. (Good call...but doesn't really explain the pumping up business does it?...)

As far as the thing stalling when you pump the brakes? That's one of my oldest tricks for setting the idle on older carb'd cars...pump the brakes, adjust the idle mixture 'till it quits stumbling, call it good.
When you pump the brakes, you are basically introducing a bit of air into the intake, causing the mixture to lean out a bit for a second.
So, either you need a complete tune up, or need to fix another vacuum leak somewhere else.


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## KrAzY (Sep 29, 2010)

jdgrotte said:


> Bleed all 4 brakes, not just the front ones. If you emptied out the master cylinder because the front brakes went to shit and/or swapped out the master cylinder, you probably introduced air into the rear brakes too.
> The brake booster holds a "vacuum" provided by the engine. Not pressure. And should hold that "vacuum" after you shut the engine off, I'd say at least overnight. If it's not holding a good vacuum, likely the check valve on the vacuum line (if installed) is bad. If you hear a distinct hissing with the engine running and it's coming from the booster, the booster is likely bad.
> 
> You seem to be getting "told" a lot of things...a lot of misinformation. As was stated last year (http://www.nissanforums.com/hb-truck/162845-valve-lifter-tapping.html), stop listening to your friends 'cause apparently they are, for the most part, idiots. I'd bet if you got a Haynes manual or something similar (FSM?), you'd get a lot better troubleshooting and maintenance information. Figuring out brake problems isn't rocket science or brain surgery.
> ...


So when i pull the vacuum line off the booster after shutting engine off and i hear air escaping for a second or 2 is that just the vacuum escaping that you say should be there overnight? If so then it sounds like the booster is holding vacuum to me and i just thought it was air coming out not vacuum. 
We have bleed the lines many many times and got nothing but fluid out of the bleeders on mc side and at the calipers and drums. However the new MC was just bolted back up without any adjustment to the pushrod on booster first i wasn't aware it had to be adjusted.

But i discovered something new about a hour ago i never noticed before, When you pump the brakes the resevoir drops in fluid level then when ya release the peddle it slowly rises back up to the full line again, Like the fluid is being sucked down somewhere then is pushed back into MC again when peddle is not being pumped anymore.


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## jdg (Aug 27, 2009)

KrAzY said:


> So when i pull the vacuum line off the booster after shutting engine off and i hear air escaping for a second or 2 is that just the vacuum escaping that you say should be there overnight? If so then it sounds like the booster is holding vacuum to me and i just thought it was air coming out not vacuum.


Overnight give or take. As long as when you start the engine the "power brakes" are "right there", I wouldn't worry about it too much past that.



> But i discovered something new about a hour ago i never noticed before, When you pump the brakes the resevoir drops in fluid level then when ya release the peddle it slowly rises back up to the full line again, Like the fluid is being sucked down somewhere then is pushed back into MC again when peddle is not being pumped anymore.


Because that fluid is getting pushed down the lines, into whatever air is in the lines, causing a nice frothy mixture in the lines/calipers/wheel cylinders/whatever, and getting pressurized. Fluid doesn't compress, *AIR* does.
When you quit pumping, the brake fluid/air mixture depressurizes, comes back out of the frothy solution back into normal fluid, and hence the fluid in the reservoir rises.

Might help if you fully describe your method of bleeding the brakes...'cause I think it, rather than your brakes, are faulty...and your mechanic friends are actually the inexperienced idiots (yes, original posts get thru to emails, before you edit them).


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## Grug (Aug 20, 2009)

Hey Krazy...how are you making out? Any progress?

My only thoughts on your issue is that you've had a lot of brake components removed which means a lot of air has entered the system. If you have no leaks anywhere, then you're working with a closed system that, somewhere, is hiding air.

Bleed, bleed and bleed again. Of course, always keep your eye on the reservoir while your bleeding to make sure the level is 'safe'.

Considering advice from everyone is good...acting on it is another story. Pretty deep, eh? 

Keep us posted and good luck, man!


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## KrAzY (Sep 29, 2010)

Thanks for the advice guys i lost my help so didn't get to anything else today because i can't do it by myself takes 2 to bleed, But i did discover a new problem or one that was allready there and just didn't notice before.

When i was pumping the peddle earlier by myself listening for any air leaks on the booster or leaks outside or inside cab i noticed some air escaping from where the MC bolts up to the booster when i pumped the peddle. I retightened the bolts thinking they were too loose but it's still doing it, I'll post back about what else i find when i can get some one to come over and help me bleed the lines again but it may be the air is being drawn in right there at the booster and MC anyway.


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## jdg (Aug 27, 2009)

You can bleed the brakes by yourself.

Get a piece of clear tubing, submerge it in a jar full of fresh brake fluid, put the other end of the tubing on the bleeder screw of the caliper/wheel cylinder, open the bleeder screw and leave it open, pump the brakes *ONCE*, check/refill the master cylinder, check the jar to make sure the tubing is still submerged, do it again. And when you get done with each individual brake, don't forget to close up the bleeder screw.
Start with the back right, back left, front right, front left. 

You'll likely want to go out and buy a rather large can or two (or five) of good brake fluid. Don't reuse old stuff and close the top on the can when you're done pouring it out. Brake fluid is hygroscopic and will go bad quick.

Basically, you're flushing out the entire brake system from master cylinder down to the wheels. Short of pressure bleeding and using a turkey baster up at the master cylinder, it's arguably the most-bestest way of bleeding the brakes...completely.

And don't kid yourself. You're not going to bleed the brakes by pumping the brakes once, twice, or even 10 times. It might take maybe 50 pumps for each of the rear brakes and another 20-30 each for the front ones. The master cylinder doesn't move a whole lot of fluid per pump.

You can either do it right, or dick around for another few weeks, give up and take it to a shop and have them do it right and pay thru the nose. Your choice.


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