Squishy brakes on 1996 GMC Sierra K1500 Z71?
 

I replaced the front pads on my 96 GMC Sierra Z71 this weekend and the brakes never came back to feeling right. The pedal goes almost all the way down to the floor before the brakes engage. When they engage, they seem to work fine.

I didn't bleed them since I didn't open the system. I just removed the front calipers, squeezed the pistons back and installed new pads. When I was finished I started up the truck and pumped the brakes to take the slack out and they never firmed up right.

I noticed that the brake fluid was a little low, so I topped it off this afternoon. This evening when I got home, I checked it again and it was a little low again, so I put the rest of the bottle in. It doesn't seem to be leaking as there is no oil on the concrete beneath the truck.

I saw one post that mentioned the bleed pin on the ABS module, so I tried to push it down while a friend pushed the brakes, but it is impossible to hold down when the brakes are pushed.

I live on a dirt road so I took the truck out and ran it up to about 35 MPH then slammed the brakes on in order to get the ABS to cycle. It didn't seem to. The brakes locked up and I slid to a stop. When I tried to go again, the front brakes were locked tight until I pumped the pedal to the floor and released it, then they released and worked again, but still squishy. I turned around and tried again with the same result, except this time it felt as if the ABS was working a little, but the front brakes still locked tight until I cycled the pedal to release them again.

Today the brake light came on and stayed on. I am going to go over to a friend's house to use his OBD2 reader, and when (if) that turns up any codes I'll let you know.

No codes, but whilst exercising the ABS system, I forced the issue. The right rear wheel is leaking fluid now pretty good. It's strange that changing the front pads would cause a problem with the rear slave cylinder. I'll pull the wheel and have a look at what's leaking back there. The inside of the wheel appears to have been collecting oil from a slight leak there for the past few days but now it's making quite a puddle on the concrete under the axle right there.

Upside is that the ABS seems to be cycling properly now however the front brakes still lock completely up whenever I slam the brakes on and hold them until I'm stopped. I have to cycle the brakes to get the front ones to release so I can move again. Is this normal? I've had the truck for 22 years and never noticed that before.

So apparently the cylinder on the rear-right had ruptured. I bought this (https://www.rockauto.com/en/moreinfo...158230&jsn=464) so for $120 I'll have all new brakes on the rear of the truck. That should ficks it.

Though some replies giving me a little guidance would be good.