Author Topic: My 84 K10 could use better brakes..What should be done?  (Read 3255 times)

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #30 on: May 03, 2020, 09:22:50 PM »
The flex line in the rear looks like it had been changed out recently before I bought the truck but it is just a factory style line.  What happens to these lines to cause issues?  I looked up some stuff regarding the proportioning valve and the symptoms listed sounded exactly like what I have going on.
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline ehjorten

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #31 on: May 04, 2020, 09:14:57 AM »
You can sometimes get a flap of material that comes loose inside the flex line that will "flap" over the opening and restrict fluid flow.  Your proportioning valve could be the culprit though.  Have you tried pushing the reset button at the front of the valve?  There should be a rubber bulb at one end of the proportioning valve.  If the system becomes unbalanced and the valve travels to one side, that button lets you push the valve back into position.  Sometimes the valve can be difficult to get reset and you will need a tool to help you move it.

Here is a decent troubleshooting guide: https://www.classicperform.com/TechBook/BrakeTroubleshoot.htm#testprop
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #32 on: May 04, 2020, 09:43:43 PM »
You can sometimes get a flap of material that comes loose inside the flex line that will "flap" over the opening and restrict fluid flow.  Your proportioning valve could be the culprit though.  Have you tried pushing the reset button at the front of the valve?  There should be a rubber bulb at one end of the proportioning valve.  If the system becomes unbalanced and the valve travels to one side, that button lets you push the valve back into position.  Sometimes the valve can be difficult to get reset and you will need a tool to help you move it.

Here is a decent troubleshooting guide: https://www.classicperform.com/TechBook/BrakeTroubleshoot.htm#testprop

Thanks!  Maybe I should try replacing the rear flex line before I go farther?  I have checked the proportioning valve reset but it seems that it is already in the correct position and I was thinking that the end where that is deals with the front brakes.  I have tested for continuity and also with a test light like the trouble shooting article showed with no luck there so maybe there isn't a problem with the proportioning valve?  I have also tried stomping on the brakes very hard multiple times as I read that could reset the valve but haven't had any luck at all.
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline JohnnyPopper

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #33 on: May 04, 2020, 09:58:53 PM »
Getting closer...
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #34 on: May 05, 2020, 07:34:19 AM »
Getting closer...

Hopefully!  With my luck the last piece I try to replace or repair will be the culprit and I will have made the entire system new in the process lol!
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline JohnnyPopper

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #35 on: May 05, 2020, 04:24:54 PM »
Yeah, like finding a lost item "the last place you look"!

Hope this is over for you soon... :o ;)
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline roundhouse

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #36 on: May 16, 2020, 09:01:16 AM »
I like the adjustable proportion valves
They are nice if you have larger tires etc
Ive even used two of them on the back axle to be able to balance each wheel
I once had a truck with 35 inch tires and a 14 bolt 3/4 ton axle and we replaced everything, lines, wheel cylinders, shoes, drums , hardware etc and the right rear always locked up first
We finally installed an adjustable prop valve on the axle for each wheel to solve it


Id also replace the flex line

If a new flex line doesnt solve it Id get a pressure gauge made for brake systems

And start by hooking it to line at the wheel cylinder, then hook it to the end of the flex line
Then hook it to The front of the flex line and So on at every junction till you isolate the problem

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #37 on: May 17, 2020, 04:16:26 PM »
Well I spent some more money and didn't get anywhere.  I replaced the rear axle flex hose with a skyjacker braided hose and I also replaced the rear axle hard lines since that was pretty cheap and easy.  After some very thorough bleeding they work the same and will barely slow the rear wheels down when I have it up on jack stands and have the truck in gear idling.  I can put a pressure gauge on to test but I know I'm low on pressure to the rear.
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #38 on: May 22, 2020, 08:56:26 PM »
Bought some more parts and went in the upgrade on the cheap direction but still no real progress.  I changed out the front calipers and pads and went to the 3/4 ton hd brake caliper and a quality pad and even though the truck already had aftermarket braided lines the new calipers required a different style banjo end so I got a new set of sky jackers braided hoses.  I also swapped out the master cylinder with a new one for a 2001 chevy Tahoe with vacuum booster application over the hydroboost.  I read many forums stating this was a good improvement over the stock 1984 setup.   I gravity bled everything and that went really well and I will follow up with some manual bleeding at some point but all in all the brakes are the same.  I'm thinking the last piece of the puzzle has to be the combination valve even though all testing showed it was fine. 

Should I simply install a new combination valve or remove it , and T the front lines along with adding an adjustable valve for the rear?
« Last Edit: May 23, 2020, 10:44:22 PM by 84Silverado4x4 »
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline VileZambonie

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #39 on: May 23, 2020, 07:49:27 PM »
Stock combination valves are fine. The more you deviate from the factory setup the more Frankenstein the truck becomes. The factory braking system will lock the rear brakes easily in a hard stop. You've definitely missed something!
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Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #40 on: May 23, 2020, 10:38:04 PM »
Stock combination valves are fine. The more you deviate from the factory setup the more Frankenstein the truck becomes. The factory braking system will lock the rear brakes easily in a hard stop. You've definitely missed something!

Wish I could figure out what that is.  This truck has never had good brakes since the day I bought it and everything I try makes no change.  I'm down to the combination valve that passes all the tests I've been told to try and the last remaining item would be  the booster and that seems fine and passes the simple tests also.  I'm not a stranger to brake work and install complete new systems on a hand full of vintage vehicles yearly with great success with both aftermarket and oem parts so I'm scratching my head on this one.  About the only issue we ever run into is when the camshafts are borderline for vacuum brakes and we have to go a different route like hydro or electro boost systems.

I'm about ready to say thats as good as it gets and just drive it.
« Last Edit: May 23, 2020, 10:49:43 PM by 84Silverado4x4 »
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt

Offline roundhouse

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #41 on: May 23, 2020, 11:08:54 PM »
Bypass the combination valve and see what happens

You could also have a pinched line between there and the back axle

If you want to find out where the problem is
You need to get a gauge and start testing it at every junction starting at the wheel cylinders

Offline 84Silverado4x4

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Re: My 84 K10 could use better brakes..What should be done?
« Reply #42 on: May 23, 2020, 11:24:11 PM »
Bypass the combination valve and see what happens

You could also have a pinched line between there and the back axle

If you want to find out where the problem is
You need to get a gauge and start testing it at every junction starting at the wheel cylinders

I'll snag the gauge from work and check it out.  Can the rear lines on the frame be replaced and fished through easily enough if need be or do the bends and tight places make it nearly impossible?
84 Silverado Reg Cab Shortbox 4x4
4" lift with 35's
5.3 vortec, 4l60e, np208, dana44, GM 12 bolt