Brakes not working properly

  • 4.3L
  • V6
  • 4WD
  • 200,000 MILES
So I have the vehicle listed above LS model. About 6 months ago my brakes started acting up and eventually stopped working all together. After some time trying to fix them I determined that the ABS module was bad. I didn't have the money to buy a new and wasn't about to buy a used one from the junkyard because I feel that would only be a temporary fix anyways before it would do the thing and stop working.I decided to bypass the ABS and after a few days I got the brakes working again but only for about 2 days. They started making a hissing noise and I would have to pump them for them to work. Then they stopped working all together again. So the vehicle set for the 5 or 6 months with the master cylinder dry with the exception of me starting it and driving it around the park I live in just to run it so something else didn't happen to it because I believe that just setting for a long period can ruin an older vehicle. Recently I started to try and fix them again and discovered the master cylinder was now bad because it was leaking onto the booster. I decided to replace the booster and master cylinder and bout the parts brand new. Also I bought new line and fittings and flared them myself using a flare tool I bought for like $8.00. Also bought 2 new brake hoses for the front 2 calipers. Since I was still bypassing the ABS I also bought a line T for the front brakes, and left the back brakes as they were and just used a connection fitting to connect new line to the old. After getting all the lines ran and installing the new booster and master cylinder before attaching the lines I did a bench bleed to the master cylinder with is on the vehicle using an assistant to pump the brake until no air bubbles were present. Then I attached the lines and had a hard time getting the fluid to the go through the lines to the calipers. After I started to finally get fluid to the calipers and some pressure I found the T I installed was leaking causing air to enter the line and also causing air to get into the master cylinder so I had to bench bleed it several times. I got the T fitting to stop leaking and finally had good fluid flow at the calipers and seemed to have no air in the lines. Keep in mind I had the line going to the back brakes capped off with no leak and did a bleed to it before bleeding the fronts. So with good fluid flow and 2 days bleeding them I still can't get the calipers to work. At times it seems like they are building more pressure but then they don't. I know with the ignition off if you depress the brake pedal they should get so stiff you can barely move the pedal but not these. They seems to not build any pressure at all. I've pulled off the calipers and depressed them using a c clamp and still they won't work. I'm completely stumped by this. Could the calipers now be bad because they have set for so long not being used? It has been 6 or 7 months since they last worked. Also should I maybe try the hooking up the back brakes and bleed them to see it they will work and maybe cap off the line going to the front as to make sure air doesn't get in the system? Please help.
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have the same problem?
Monday, April 12th, 2021 AT 9:03 AM

1 Reply

Hello. If there are no leaks, and you're sure that the lines are full and bled then I'd suspect that the master cylinder is faulty. An internal seal is allowing fluid to blow by it, keeping the pressure from building. I would suspect there is air in the lines. These guides can help you fix it:



Please run down these guides and report back.

My suggestion would be to replace that master cylinder again. I think that'll get you going. Good luck and keep us posted.
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Monday, April 12th, 2021 AT 2:27 PM

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