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1976 C10 - No Brake Fluid to Front Driver Side


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beems
New User

Apr 20, 2017, 11:36 AM

Post #1 of 14 (133 views)
1976 C10 - No Brake Fluid to Front Driver Side Sign In

Vehicle: 1976 C10 RWD Pickup
Brake System: Rear Drum, Front Disk

So in learning to do some basic mechanical stuff on my old, inherited truck, I've come across a brake problem I don't know how to troubleshoot. The truck has always pulled to the right when I braked, so the problem has likely been going on for a long time.

The rear drums have had new hardware kits and hardware cylinders, and the front has new calipers and pads.

The brake system was bleed successfully until I got to the last wheel - the front driver side. I have no fluid at that wheel, and the rest of the system is now pretty "tight" after bleeding (the brakes are set a little snug against rotors/drums after the bleeding of the first 3 brakes).

I'm assuming the problem is with the proportioning valve because my father said that the brake light was on so he unplugged the indicator from the proportioning valve. This leads to the conclusion that the proportioning valve has been tripped for years or even decades for all we know. Am I on the right track, or where should I start to troubleshoot this? If it is the proportioning valve, is there any way to "reset" it or do I need to buy a new one?

Thanks in advance,
Beems


Hammer Time
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Apr 20, 2017, 12:00 PM

Post #2 of 14 (128 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

I don't know how you got to proportioning valve but it sounds like a bad rubber flex hose. I would replace both front and in the process, make sure the caliper pistons and slides are free.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



beems
New User

Apr 20, 2017, 1:39 PM

Post #3 of 14 (122 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

Sorry for my ignorance, but if the proportioning valve has tripped won't it cause the "Brake" light on the dash to light up? The sensor is unplugged from the proportioning valve right now so of course right now the dash light isn't on.


Hammer Time
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Apr 20, 2017, 1:51 PM

Post #4 of 14 (117 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

I've been in this business 50 years and I think in that time I have changed one proportioning valve.

If your brake light is on, that means there is an imbalance in the 2 braking systems. You need to find out where the air is in the system. A proprtioning valve won't give you the symptoms you refer to. Check what I stated the first time.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Apr 20, 2017, 1:51 PM)


kev2
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Apr 20, 2017, 2:09 PM

Post #5 of 14 (109 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

this is a combination valve AKA proportioning - it may need to reset, recenter the valve after it has 'latched' either forward or rearward.
Often the switch is removed to aid valve (spool) movement - try google resetting combination or proportioning valves - pictures will help you ID which exact model.


Hammer Time
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Apr 20, 2017, 2:13 PM

Post #6 of 14 (106 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

On this truck that valve separates the front from the rear, not left to right so I don't see how it can possibly cause pulling when braking or no fluid to one wheel.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Apr 20, 2017, 2:18 PM

Post #7 of 14 (102 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

Flex hose - no waste not to anyway, both as HT said earlier,


T



beems
New User

Apr 20, 2017, 2:22 PM

Post #8 of 14 (96 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

Thanks everyone - I'll go snag the front flexible brake hoses.

And Hammer Time, you gotta' relax man, you're going to give yourself an aneurysm. You just said "I don't know how you got to proportioning valve" so I responded. I wasn't in any way saying you were wrong, so please take it easy.


Tom Greenleaf
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Apr 20, 2017, 2:42 PM

Post #9 of 14 (94 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

Everyone calm down! beems: It's not the proportioning valve - I'm near sure because they don't fail at all usually and can't really that way.


Pinched line doesn't usually even stop flow. A bleeder could that you can clean out or just get a new one. Learn to love this truck there isn't much simpler for much out there as this vehicle goes, parts available and not costly,


T



Hammer Time
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Apr 20, 2017, 2:47 PM

Post #10 of 14 (90 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

I wasn't even responding to you. I was more responding to Kev who seemed to be pushing the proportioning valve idea.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



kev2
Veteran
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Apr 20, 2017, 3:47 PM

Post #11 of 14 (81 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

WHOA - Don't shoot the messenger I also think flex line - comment was to have poster look into valve operation - .
There are several different types, and as I said 1976 is not fresh in my mind. learn before changing it was my thought


Tom Greenleaf
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Apr 21, 2017, 6:46 AM

Post #12 of 14 (61 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

Still, please calm down. It is fresh in my mind though - still have impossible to find flare nuts that fit into the "combination valve" is what it's called as it double to set off (light up) brake warning light.
They can get stuck when whole FRONT or WHOLE real has a total pressure loss almost always a rusted out line. If you keep driving it then it might stick blocks off failed system of the two - front and rear only not left and right.
If both of a system - the fix if you live 100 years to have that problem is open the stuck end when fixed right at the master cylinder even pushes it back and then self centers. This isn't the issue so can forget that.


Why picking on one wheel: Can only be a few things......... 1st bad flex hose. 2nd knowing the bleeder works and is clear - take it out and clean it with drill bits. 3rd is a brake line was smashed - any way from a rock, hard hit by mistake by something in it's life?


The rarer other is the caliper isn't any good or pins all screwed up. They rebuild these again and again, rig up a bleeder from a lousy core with a brass insert or who knows? Not all come out well but look nice in the box.


The real disaster hasn't been mentioned is if this was contaminated by something other than brake fluid all rubber parts could fail in assorted ways. Clue would be the rubber seal inside the cap of the reservoir would show swelling if an OIL was introduced. If so make this another whole thread as that would be a serious problem with assorted first symptoms then an involved fix,


Tom



(This post was edited by Tom Greenleaf on Apr 21, 2017, 6:49 AM)


beems
New User

Apr 21, 2017, 11:38 AM

Post #13 of 14 (47 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

Tom, thanks for the detailed tips.

The bleeder shouldn't be the issue because as new calipers were installed I removed everything up to and including the banjo bolt. So at that point, effectively right off the flex line, I have no fluid flow. When I pulled it off the caliper fluid flowed, but apparently only what was in the line. After that was gone I get nothing even when pressing the brakes hard. Since we know the problem exists above that, we can also rule out the caliper. I'll grab a set of flex hoses on my way home (even though one is good, they're only about $14/each so I'll just swap them both. Once I get those swapped I'll be sure to look around for a smashed hard line.

Notably, the rubber seals in the reservoir caps look good to my untrained eye (still flexible and don't appear swollen).

Thanks again for all the support and tips everyone. I'll be sure to swing back by here as I go through this truck piece by piece.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 21, 2017, 1:21 PM

Post #14 of 14 (41 views)
Re: 1976 C10 - No Brake Fluid to Front Driver Side Sign In

Ya - just do them but do yourself a favor and put some PB penetrating oil on the frame end of the hose now AND especially where metal line goes into flare nut right there. If that line that loves to twist up busts off it's a harder line to make up new so try hard not to ruin it.


Do know the metal lines you make yourself with raw line or straight line with ends already on that might not be yours so you bend and flare ends yourself. That stuff isn't sold new ready to just put on,


T







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