Author Topic: 84 C10 Brakes  (Read 28404 times)

Offline Ronno6

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84 C10 Brakes
« on: June 10, 2018, 09:25:02 AM »
I have replaced the rear wheel cylinders, calipers and master cylinder.
Bled master cylinder on the bench and on the truck.
I have done 1 man and 2 man bleeds, gone thru 2 quarts of fluid.
No air visible in the bleeder tubing.
No hoses,lines or joints are leaking.
Brakes are hard as rocks without vacuum boost, but, when engine is
running, the pedal goes way down, far past the stopping point when engine is off.
The truck will stop, but I am not confident that things are as they should be.
Sounds to me like my new (not rebuilt) master cylinder is defective.

What say y'all??
« Last Edit: June 10, 2018, 09:51:48 AM by Ronno6 »
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline bd

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Re: 84 C10 Brakes
« Reply #1 on: June 10, 2018, 10:54:27 AM »
Power brakes feel softer than manual brakes.  It's the nature of the design.  Recheck the rear brake adjustment.  Make sure you adjust the shoes with the park brake cable adjustment backed off; that is, always adjust the shoes before adjusting the parking brake cable. 

If adjustment access for the rear brakes is through a window in the drum, remove the rear wheels, flip three lug nuts per side so the taper is pointing outwards and snug the drums to the axle flanges.  Adjusting one side at a time, tighten the star adjuster for each rear brake until you cannot rotate the drum by hand.  Then, using a small hook through the window to pull the adjuster away from the star, back off 12-15 clicks (teeth), or until you can rotate the drums with very little brake drag.  After the shoes are adjusted, readjust the park brake cable.
« Last Edit: June 10, 2018, 12:04:49 PM by bd »
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Ronno6

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Re: 84 C10 Brakes
« Reply #2 on: June 11, 2018, 03:27:03 PM »
I followed bd's instructions and there is no change.

The pedal is hard as a rock with engine off, and seems to be stiff when I apply more pressure with engine running.
When I ease off the pressure, the pedal travels downward, but stops before hitting the floor.
I believe this indicates the fluid bypassing an internal seal in the MC.
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline bd

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Re: 84 C10 Brakes
« Reply #3 on: June 11, 2018, 03:40:29 PM »
Try depressing the brake pedal lightly with the engine running.  Does the pedal gradually drop with light constant pressure?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Irish_Alley

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Re: 84 C10 Brakes
« Reply #4 on: June 12, 2018, 07:17:37 AM »
couple questions, why did you replace all those parts? and thats about it for now ;)
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Ronno6

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Re: 84 C10 Brakes
« Reply #5 on: June 12, 2018, 07:21:39 AM »
Try depressing the brake pedal lightly with the engine running.  Does the pedal gradually drop with light constant pressure?

Yup.
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline Ronno6

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Re: 84 C10 Brakes
« Reply #6 on: June 12, 2018, 07:23:59 AM »
couple questions, why did you replace all those parts? and thats about it for now ;)

Rear cylinders were leaking.
Calipers had the bleeder valves frozen.
Master cylinder acted a bunch like the new one....pedal went way down and would not pump up.

What is the other question??
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline Irish_Alley

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Re: 84 C10 Brakes
« Reply #7 on: June 12, 2018, 08:28:07 AM »
other question/s will follow. did you replace any hoses?
does the pedal first feel firm (like it should) then once you go past (lets say) 60% it goes straight to the floor or does it pretty much go straight to the floor?
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline bd

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Re: 84 C10 Brakes
« Reply #8 on: June 12, 2018, 08:53:23 AM »
Try depressing the brake pedal lightly with the engine running.  Does the pedal gradually drop with light constant pressure?

Yup.

Recheck the entire system for fluid leaks, including close inspection of every inch of the hard and soft lines and their connections.  If there are no leaks and the brakes are properly adjusted and bled then your original posit regarding a bypassing M/C may be correct.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Irish_Alley

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Re: 84 C10 Brakes
« Reply #9 on: June 12, 2018, 09:51:37 AM »
bd do you think the old MC and new MC could have the same problem? i mean i know stuff can be bad right out of the box but couldnt the problem lay in the brake lines/hoses
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Ronno6

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Re: 84 C10 Brakes
« Reply #10 on: June 12, 2018, 10:11:41 AM »
bd do you think the old MC and new MC could have the same problem? i mean i know stuff can be bad right out of the box but couldnt the problem lay in the brake lines/hoses

That thought had occurred to me.
The MC was acting in a similar manner to the one on my F150.
I replaced it and all is fine.
As the C10 is 34 years old and had been sitting for at least 4 years, I figured it to be time.
If the new MC is good, then the old one probably was as well.
But if one is bad.................

I have not, as of this juncture, replaced any hoses or lines.
There are no visible leaks anywhere.

The snap ring on the original MC has the ears broken off.
Dunno if that means that someone had attempted to disassemble and it went wrong.............

At any rate, I'm gonna do a complete re-inspection and check parking brake adjustment.
I'll see how it is then.
« Last Edit: June 12, 2018, 10:44:36 AM by Ronno6 »
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline Irish_Alley

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Re: 84 C10 Brakes
« Reply #11 on: June 12, 2018, 11:18:19 AM »
one thing that im thinking is a hose is blistering causing the fluid to go to a hose bubble and not the the wheel cylinder or whatever
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline bd

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Re: 84 C10 Brakes
« Reply #12 on: June 12, 2018, 11:24:12 AM »
bd do you think the old MC and new MC could have the same problem? i mean i know stuff can be bad right out of the box but couldnt the problem lay in the brake lines/hoses

I'm not there to make firsthand observations, so must draw from experience with the posted symptoms balanced against how the system functions while doing the best I can to filter out assumptions that have been made.  Based on what has been posted, I suspect an adjustment issue and/or residual air trapped in the system or a simple lack of familiarity with the "feel" of GM power brakes to be the most likely cause(s).  Don't make the mistake of believing that any particular symptom has only one cause.  The original symptom may have been repaired only to be replaced by a similar substitute having a different cause.  Hence, all we can do at a distance is make suggestions for checks to be performed and evaluated in the hope that it is sufficient for the OP to discover the truth and resolve the issue.  Do you disagree?

There are two wrong decisions to make: one is to do nothing, the other is to "overthink" the symptoms rather than just looking.  Filter out that which you can definitively through observation and what remains is probably the cause.

...At any rate, I'm gonna do a complete re-inspection and check parking brake adjustment.
I'll see how it is then.

I think this ^^^^ is a good decision.

one thing that im thinking is a hose is blistering causing the fluid to go to a hose bubble and not the the wheel cylinder or whatever

Checking the hoses while an assistant steps on the brake pedal is part of a basic inspection that may have been overlooked initially.  If so, it should be done now.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Ronno6

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Re: 84 C10 Brakes
« Reply #13 on: June 12, 2018, 11:31:10 AM »
Checking the hoses while the petal is applies id a good suggestion.
I have noticed that the rear brakes will lock up when sufficient pedal force is applied.
I had not mentioned this earlier because until I replaced the shoes and drums, the shoes and drums had been contaminates with brake fluid or grease, which will cause the drum brakes to grab.
So, new drums and shoes, adjusted (parking brake as well) and rear braking is balanced side to side,
but still will lock up earlier than the discs in front.

Possibly a hose or hoses have some give which they should not.
As the pedal is rock solid without engine vacuum, maybe manual only force is
insufficient to cause a hose to swell, but vacuum assist may provide the force to do so.

On to this step.......
« Last Edit: June 12, 2018, 11:34:44 AM by Ronno6 »
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline Ronno6

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Re: 84 C10 Brakes
« Reply #14 on: June 12, 2018, 11:36:14 AM »
Checking the hoses while the petal is applies id a good suggestion.
I have noticed that the rear brakes will lock up when sufficient pedal force is applied.
I had not mentioned this earlier because until I replaced the shoes and drums, the shoes and drums had been contaminates with brake fluid or grease, which will cause the drum brakes to grab.
So, new drums and shoes, adjusted (parking brake as well) and rear braking is balanced side to side,
but still will lock up earlier than the discs in front.
And the pedal still goes rather far down.
With regard to m F150 brakes, when I applied them, I could feel braking occur, then subside.
I do not experience this with the Chevy.

Possibly a hose or hoses have some give which they should not.
As the pedal is rock solid without engine vacuum, maybe manual only force is
insufficient to cause a hose to swell, but vacuum assist may provide the force to do so.

On to this step.......
You can lead a man to water, but yoiu can't keep him from pissing in it.