brake system trouble

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e1than89
Posts: 4
Joined: Thu Apr 03, 2014 7:31 pm

brake system trouble

Postby e1than89 » Thu Apr 03, 2014 7:42 pm

Well to start off i have had this 84 king cab truck 2wd for 5 years. always had brake problems. finally had even funds to do something about it. figured master cylinder was bad so got a brand new one done a instructions said. put it together and had descent brakes. desided to bleed brakes and i couldnt get front brakes to bleed. i took off line at the mc to front brakes and still nothing coming out. plz help


e1than89
Posts: 4
Joined: Thu Apr 03, 2014 7:31 pm

Re: brake system trouble

Postby e1than89 » Thu Apr 03, 2014 9:29 pm

i bench bleed the mc before hooking it. the back brakes bleed fine. the front brakes when i first cracked it it shot out a stream of brake fluid. then nothing on the second try. does anyone have any answers? should is i bench bleed it again? is it my brake booster? is there something im not doing?

xsdg
Posts: 41
Joined: Mon Nov 18, 2013 7:45 pm
Car: 1985 Datsun 720

Re: brake system trouble

Postby xsdg » Fri Apr 04, 2014 11:52 am

You _must_ bleed the proportioning valve _first_. It sits under the passenger seat, on the inside of the frame rail. Bleed screw is on the top. Once that's done, bleed the rears and then the fronts.

If that doesn't fix it, the next step is to re-bench-bleed your MC. You can try just pulling off the flare fittings, attaching the bench bleed fittings with the MC still mounted in the car, and doing it that way. I can't find it right now, but I had followed a video on YouTube that recommended bleeding it with the piston end of the MC lower than the other end, and then doing it again with the piston end higher than the other end. I found that changing the angle like that did let me get more air out. With it mounted in the vehicle, you could just jack up the front or rear (and support with jack stands) while you're re-bleeding.

e1than89
Posts: 4
Joined: Thu Apr 03, 2014 7:31 pm

Re: brake system trouble

Postby e1than89 » Fri Apr 04, 2014 6:51 pm

Thanks for the help. i will try this again in a couple days. ill post a reply of how it goes. how can i tell if the booster is bad?

e1than89
Posts: 4
Joined: Thu Apr 03, 2014 7:31 pm

Re: brake system trouble

Postby e1than89 » Fri Apr 04, 2014 6:53 pm

What do i do if driver side back wheel doesnt have bleeder?

xsdg
Posts: 41
Joined: Mon Nov 18, 2013 7:45 pm
Car: 1985 Datsun 720

Re: brake system trouble

Postby xsdg » Sat Apr 05, 2014 1:49 am

The brake booster has no fluid inside of it, and will not affect whether or not you can bleed the brakes.

You can check if your booster has a vacuum leak by pressing the brakes, turning the car off with the brakes still pressed, and seeing if the pedal pushes back on your foot. If so, the vacuum level in the booster is decreasing after the car shuts off (which should not happen). If the pedal stays down, it's good to go.

The only thing the brake booster does is to reduce the amount of effort required to actuate the brakes. If it's not working properly, it takes (a lot) more effort, but you should still be able to slow down.

And I'm not sure what you mean by the cylinder doesn't have a bleeder. Is it missing, or just replaced with some non-bleeder screw? If the system holds pressure at all, then it's at least not _open_, which is good. You could just replace all the bleed screws with new ones, or with ones from junkyard trucks. But it's hard to say without getting a better idea of what's actually going on.

brant914
Posts: 1
Joined: Wed Apr 09, 2014 1:55 pm
Car: 1986 720

Re: brake system trouble

Postby brant914 » Wed Apr 09, 2014 2:03 pm

e1than89 wrote:What do i do if driver side back wheel doesnt have bleeder?

trying to help a friend and found the same 2 problems:

1) no bleeder on the rear passenger side drum

2) where is this proportioning valve?.... I have pressure and have bled the front axle, but have zero pressure coming to the rear axle.

thanks in advance
brant

xsdg
Posts: 41
Joined: Mon Nov 18, 2013 7:45 pm
Car: 1985 Datsun 720

Re: brake system trouble

Postby xsdg » Sun Apr 13, 2014 11:04 pm

"You _must_ bleed the proportioning valve _first_. It sits under the passenger seat, on the inside of the frame rail. Bleed screw is on the top. Once that's done, bleed the rears and then the fronts."

User avatar
Brownietruck
Posts: 2
Joined: Tue Nov 17, 2015 1:08 pm
Car: 1985 Nissan KingCab 4x4 Z24

Re: brake system trouble

Postby Brownietruck » Sat Dec 22, 2018 9:37 pm

This is somewhat unrelated but I thought I would try anyway......
I just broke my driver side rear bleed valve off. Does anyone know of any tricks on how I would get the broken part out? I am all ears (and apparently thumbs) :gotme

Best regards,
Mark


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