Author Topic: Brake Gremlin  (Read 20852 times)

Offline VileZambonie

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Re: Brake Gremlin
« Reply #30 on: July 03, 2016, 07:32:30 pm »
Make sure you have the correct adjusters on each respective side. Double check the drums, try swapping the drums L to R and see what happens.
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Offline TheWaterboy

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Re: Brake Gremlin
« Reply #31 on: July 05, 2016, 09:16:52 am »
Hey Everybody,

Thank you to everybody that has responded. I have now replaced the Master cylinder, I do think the seels were going out on it the pedal feels a lot better. However the original issue remains. I also pulled apart both rear brakes and checked for any mistakes, I did find one on the side that has not been giving me issues. The parking brake strut was incorrectly installed. I also cleaned the backing plate to bare metal on the "wear bumps" and applied a very small amount of anti seize to them. There are some ridges in a couple, I will need a grinder to repair. What i still need to try is swapping drums and shoes LH to RH ( I had not does this because I had replaced the driver side drum and the shoes once already and made no change ) and then replacing hard lines?? and trying new shoes?? It has to be something simple ....... I am on week 4 of trying to resolve this
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Offline VileZambonie

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Re: Brake Gremlin
« Reply #32 on: July 05, 2016, 12:37:09 pm »
If everything is correct as you say it is simply swap the drums left to right. If the drum is improperly machined there's your problem. You aren't over adjusting them are you?
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline TheWaterboy

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Re: Brake Gremlin
« Reply #33 on: July 05, 2016, 12:47:31 pm »
If everything is correct as you say it is simply swap the drums left to right. If the drum is improperly machined there's your problem. You aren't over adjusting them are you?
I am adjusting until they drag a little then backing off 4 teeth. However I also tried having them backed off enough where they were not contacting at all and the driver still slowly became over tightened again. Within my 5 mile test loop

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Offline VileZambonie

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Re: Brake Gremlin
« Reply #34 on: July 05, 2016, 12:51:25 pm »
again, do you have the correct adjuster screws on their respective sides? They are not the same L and R, even though it's been mentioned a few times I haven't seen you acknowledged this.
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Offline TheWaterboy

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Re: Brake Gremlin
« Reply #35 on: July 05, 2016, 03:40:31 pm »
again, do you have the correct adjuster screws on their respective sides? They are not the same L and R, even though it's been mentioned a few times I haven't seen you acknowledged this.
Hey sorry I thought I did . The driver side is regular thread and the passenger side is reverse thread. I do believe that is the correct positioning.

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Offline 1967KaiserM715

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Re: Brake Gremlin
« Reply #36 on: July 05, 2016, 05:14:44 pm »
 I wonder if the top anchor pin is worn, this will allow the shoe to rock forward with braking, and cause the adjuster lever to adjust the shoes out. Rather then the springs and rods working the adjuster lever.


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Offline TheWaterboy

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Re: Brake Gremlin
« Reply #37 on: July 06, 2016, 07:13:37 pm »
Okay so an update on this issue  I disassembled the rear brakes again....swapped the shoes and ground down the groves I found in the backing plate on the wear bumps and put a small about of anti seize on them. So far it has dramatically reduced the issue but not completely solved it there is a consistent sound under braking like a rhythmic scrape and an occasional squeal I took it for a ~ 30 mile trip stopping every so often to check for excessive heat. The driver side rear is still the warmest by quite a bit but no where near as hot as it was getting before. So I think the drum was over heated and will need to be turned or replaced and possibly get higher quality brake shoes? With this change in symptoms any additional thoughts??

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Offline VileZambonie

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Re: Brake Gremlin
« Reply #38 on: July 06, 2016, 07:52:30 pm »
Brakes are supposed to get hot. They work on the principal of friction and heat. If you jack it up with the wheels on and they spin freely, aren't locking up or grabbing, pedal feels good, then your only complaint should really be your noises.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline TheWaterboy

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Re: Brake Gremlin
« Reply #39 on: July 06, 2016, 09:06:36 pm »
Yes I  am aware of how brakes work and that they typically produce heat... I am not referring to a normal level of heat. Part of the original symptom with the dragging shoes obviously was the increase in heat on that corner. I have an Infrared thermometer and checked the drums on both sides in an attempt to quantify " being hot"  The passenger side was what I would consider a normal temperature at around 125-140 while the passenger side got to around 295-320 in the same trip under regular driving not exceeding 50mph on a 10-15 mile trip. Now the driver side is at 180-200 and the passenger side still at 125-140 after a 45 mile trip including highway speeds ending in the same 10 mile loop from the previous test. So I feel like I have reduced the problem. I know the drum on that side was way over temp but in my experience that would not cause that system to keep getting hot, the sound could be caused by the drum if it is warped.. maybe?? Usually it would cause a pulse from what I have seen.
Brakes are supposed to get hot. They work on the principal of friction and heat. If you jack it up with the wheels on and they spin freely, aren't locking up or grabbing, pedal feels good, then your only complaint should really be your noises.


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Offline VileZambonie

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Re: Brake Gremlin
« Reply #40 on: July 06, 2016, 09:16:22 pm »
There are many reasons the drum could be the issue aside from out of round. Simply swapping the drums would reveal if it were the issue.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline TheWaterboy

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Re: Brake Gremlin
« Reply #41 on: July 17, 2016, 12:08:58 pm »
Problem Solved!! So as i said in a previous post, i ground out the grooves in the backing plate. I thought this had pretty much resolved the brake sticking problem. I was left with a little bit of extra noise and heat coming from the same driver rear. I swapped the drums and the sound went with the drum, I looked at getting both turned but the cost was 2/3 what a new AC drum cost from Rock Auto so i went that route and also replaced the shoes with AC shoes as the ones that were on there where cheepos. It is working great now no sound or excess heat, So thanks for all the help! Glad that's over with now on to servicing the Rear diff and then a little body work.

p.s Another issue i had was I thought i got all the transmission fluid out of the converter when i had it out and filled it to spec, that was about 1.5 quarts to many.... But figured out a easy way to get that extra fluid out. My truck has a Trans cooler built into the Radiator I just detached the bottom line put a clear rubber hose on the end. Then i disconnected the power to the Coil and cranked the engine with the hose leading to an empty transmission fluid container. It pushes out a quart pretty quick so heads up if you are not careful you will drain to much. I did by about 1/2qt but putting it back in is the easy part.
86 C10 2WD LWB 350 ~ 2nd owner bought in 87 by grandfather