Author Topic: brake failure  (Read 2400 times)

Offline danmandan

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brake failure
« on: September 25, 2020, 01:06:11 PM »
Hi,, I have a 79 k10 shortbed 350 /th350 , I got a deal on a complete rear 12 bolt rear end and a 10 bolt front end ,,,,, drum to drum and rotor to rotor ,, all new parts ,,, swapped the rear out bled the brakes and drove for a bit ,, no problem,, then swapped the front end out ,,, put in all new brake hoses,calipers, pads ,,rotors,, I now have little to zero brake pedal,, I have reset the proportining valve no change and wasted now 4 and a half quarts brake fluid pumping with little to no pedal,, vacuum bled ,, pumped and pumped no pedal,, would this be the master cylinder has failed all of a suddern? proportining valve?,,, If the proportining valve went bad wouldn't I have either front pedal pressure or back pedal pressure? both reservoirs drained out when I swapped the suspension,, any ideas?? Thanks Dan

Offline bd

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Re: brake failure
« Reply #1 on: September 25, 2020, 02:49:07 PM »
Remove and bench bleed the master cylinder using fresh DOT 3 or DOT 4 fluid from a newly opened container.  Reinstall the M/C and then gravity bleed the brakes, rear and front, w/o stepping on the brake pedal.  Verify correct adjustment of the rear shoes.  Inspect the entire length of the hydraulic lines and hoses that there are no leaks.  With the parking brake released, verify that the brake warning lamp in the instrument cluster is not illuminated.  Then recheck the brake function.
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 danmandan

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Re: brake failure
« Reply #2 on: September 26, 2020, 08:48:02 AM »
Hi Rich ,, Thanks for your input,, I took your advise ,,but I ordered a new M/C instead of using the old one  "40 plus years of abuse "and it wasn't that expensive,,, it should be here today ,,going to bench bleed it and then do the swap ,, gravity bleed and go from there,,

Offline danmandan

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Re: brake failure
« Reply #3 on: September 27, 2020, 08:25:41 AM »
in progress

Offline danmandan

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Re: brake failure
« Reply #4 on: September 27, 2020, 07:48:58 PM »
Hi,, I installed the new m/c after I bench bled it ,, Bled the lines front then rear,, seems to have pedal again ,,,, didn't get to drive it yet,,,, had to go so I will test drive tomorrow

Offline bd

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Re: brake failure
« Reply #5 on: September 30, 2020, 06:08:48 PM »
What's the verdict?  How are the brakes working, now?





Also,  ^^^^  if you just flushed 4 1/2 quarts of fresh brake fluid through the brake system, why does the recovered fluid in the Coke bottle appear so dark?
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 danmandan

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Re: brake failure
« Reply #6 on: October 01, 2020, 07:01:54 PM »
Hi , Sorry for taking so long to get back but its been hectic around here ,just got to drive it yesterday , I am happy to say the brakes work just fine "finally",,     I am glad I swapped the m/c out with a new one ,I did what you said ,"bench bleed" but did it in place,  broke the fittings a little loose 1 at a time on the old  m/c while still on the truck and the rear was pumping pressure the front was nothing,,, just dripping,, so I think we pumped it to death ,, when I removed it there was fluid running out the back of the m/c ,, anyway the new one works good,, never had that happen before ,,a m/c fail ,like that,, good it happened in the driveway,, and that coke bottle with the crusty looking fluid in it  I've had for awhile now , I use it when I bleed brakes , just did a complete brake job on the wifes car and it was left over from that job and I never pitched it,, but its going away now cause I'm done ,, ended up wasting the 4.5 quarts and bought 2 more to finish this,, Thanks again,Dan

Offline bd

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Re: brake failure
« Reply #7 on: October 01, 2020, 07:26:56 PM »
Congrats!  Glad to hear you got it squared away.
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)