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Old 05-03-2012, 03:17 PM
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1986 chevy braking problems

Im new to the truck world so i need some help with my 3/4 ton chevy k20 350, the brakes i have to push down all the way and it still keeps rolling a few feet then stops, is this the nature of the beast there is no squealing when it stops just not real safe cause i slam the pedal into the floor and it keeps rolling what should i be looking for first.

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Old 05-03-2012, 03:24 PM
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Start by checking the fluid level in your mastercylinder, if its low, you need to determine where the fluid went. Could be a bad wheel cylinder or caliper, a leaking flex line to one of the front wheels or rear axle, rusted out steel lines anywhere within the braking system, or a master cylinder that is leaking internally.

What is your experience level with braking systems in general?
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Old 05-03-2012, 04:19 PM
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hey

i have done alot of brake work not so much with the drums in the rear but changing out calipers pad swapping done alot of and bleeding, I checked the master cylinder plum full to the top I checked the lines does not appear to be leaking, what I was thinking of doing is tearing it apart this weekend inspecting the brakes i just bought the truck the last guy i bought it from drove it about 15 miles all year and i live in Oregon its cold i'm thinking maybe the drum or the rotors are glazed, or maybe the rear brakes aren't working at all or there is nothing left to those pads in the rear. Tell me if I go in reverse its alot harder to stop it rolls alot longer then going forward does that have anythings to do with the rear? or could the master cylinder be going out? it stops but not real good so that's why i was thinking start with the tear down replace pads inspect the drums see if its glazed or even cracked that is what i'm thinking do you think i'm on the right path?
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Old 05-03-2012, 04:21 PM
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hey

and is there a test to chck the master cylinder to see if thats going out
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Old 05-03-2012, 05:29 PM
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Low pedal will be one of three things...badly unajusted rear brakes, air in the system or a master cylinder bypassing pressure.
I have also seen ABS units fail, not trip any warning indicator and allow the pedal to go slap to the floor.Probably not the case with your truck.
First Inspect them, service the rears and adjusters, and adjust. Inspect the fronts . make sure the pads move in the caliper mounts and are not seized.
Then check the braking action, if it improved, your good to go.If pedal is still real low, then bleed the entire system, starting at the pass rear, then drivers side rear, then go to pass front, then finally to drivers side front.
If peadal still hits the floor after all that, replace the master and rebleed.
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Old 05-03-2012, 10:20 PM
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hey

thanks i will
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Old 05-06-2012, 08:17 AM
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First make sure the brake booster is connected to the vacuum port on the back of the carburetor and that it has good vacuum. Without this connection you have brakes, but no "power" to actuate them.

On an '86 HD you may also have hydro-boost instead of a traditional power brake booster, but I think they only put that on 1 ton trucks. You will be able to tell because you won't have the large power brake booster. I don't know how to troubleshoot hydro-boost brakes.

Then check the flexible lines that go to each front caliper and to each of the drums. As they get older they will get soft and may just expand when you push the pedal, instead of pushing all the pressure to the brakes.

There is also a brake proportioning valve that is important, but if the electrical wiring is still hooked up it should give you a brake warning light if it sends more pressure to one half of the system. There is a little switch inside the valve and if there is too much pressure on one side (front vs. rear) it flips the switch and turns on the light when you press the brake pedal.

If there is unequal pressure on the front vs back brakes, it may be because of a leaking rear wheel cylinder. Wheel cylinder leaks inside the rear drums may be too small to see, but release enough pressure to affect the brakes. Leaking pistons on the front calipers should be very easy to see.

Bruce
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