98 Chevy brake problems

Old 03-08-16, 09:37 PM
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98 Chevy brake problems

So, I was having some problems with a shaking on this truck in another thread.

98 Silverado 4x4, auto trans, about 200,000 miles. Working on getting the shake out, and thought maybe I had a warped rotor. Picked up new rotors and brakes. Put the drivers side on and all went well. When I was doing the passenger side, I found that the caliper was sticking, so I picked up a new caliper.

Installed the caliper, bled the brake and all seemed well. )Took it for a ride and the shake was still there though.) However, now there seems to be a new problem.

When I took the brake fluid cover off, prior to bleeding, the side closest to the steering wheel was just about empty. The brakes were working good before I started anything with them and there were no broken brake lines. So I changed the caliper, bled the brake, had good pedal, took it for a ride and the brakes worked good.

Fast forward an hour or so, and my wife had to go to town. When she got back she said that she lost brakes in town? She was parked at a stop sign and had her foot on the brake pedal, and it just went to the floor. When she took her foot off of the brake, and reapplied it, the pedal was back. It happened twice more before she got home.

I looked things over. The cover on the brake fluid wasn't on tight, so some fluid pushed out, but the level was still good. Not much came out. No brake lines are broke, nothing leaking. Went for a test ride, and the brakes work good enough, but are very spongy and the pedal goes mostly to the floor. The brake light is now on, but the abs light isn't (has 4 wheel anti lock). The area where the master cylinder bolts to the booster has some fluid on it, but that could be from the fluid coming out of the reservoir.

If the pedal goes to the floor, and no fluid is leaking, is the master cylinder bad? Is there any other thing that can cause the pedal to go down but the system to not lose fluid? I understand that these brake systems are a pain to bleed, and I'll probably have to bring it in somewhere to do it if I change the master cylinder. Is there any way to properly bleed these without the scan tool? I find it odd that the brakes worked good when I first bled it, and then shortly after there were issues?

Any thoughts on this? Thanks for taking the time to read this.
Old 03-09-16, 03:36 AM
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One section of the master cylinder reservoir provides fluid for the back, the other for the front brakes. The rear section of the master cylinder should be for the rear brakes. I'd look closely for any signs of leaks!

IMO it's no big deal to blead/prime a new master cylinder. Most do it on a work bench prior to installation but I've always thought it was easier to do it once installed.
Old 03-09-16, 05:00 AM
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You didn't get something bled good. You still have air in the system somewhere.

Since you described it like you did, I am sure you know what your doing but, in order to bleed the system, you'll need a helper. One to pump up the brakes & hold... & one to open the bleeder & close it off. Pump again, bleed again. Make sure your helper holds that pedal down until you get the bleeder open, bled & closed. Then pump, hold, bleed, etc.

I'm not totally familiar with your general vehicle so maybe others else will confirm.
Old 03-09-16, 05:09 AM
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I had a problem like that once. After I replaced the caliper, the increase in pressure blew a line going to the rear. Look at the inside wall of each tire (wet) & inspect the line where is passes the gas tank. Are there drum brakes in the rear? Have your wife pump the brake while you look.

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