So this came up about a month ago, when I was coming home from work I was on the highway and I was coming to an exit and I hit the brakes to slow down and the pedal went the whole way to the floor and my Red Brake Light came on, But after pumping the pedal a few times the brakes came back and they were actually better than before. Then it didn’t happen again until a week or two later, the second time, the brake pedal went to the floor almost every-time I depressed it, then after that it hasn’t happened again until today, I was exiting a highway and the brake pedal went to the floor, it seems to only happen whenever slowing down from higher speeds, a week ago I looked over everything and I didn’t find a single leak, everything is dry, my pads up front are good and my shoes in the back still have meat on them. And the reservoir was almost full so I topped it off. Where should I start to find this problem? Everything I looked up said to replace the master, mine is still the original. But it didn’t fix the issue for some. My booster seems fine, maybe the seals in the master are going out? Idk, I’ve seen in some cases the abs modules get air trapped in them. Should I bleed the abs module with the bleeder it has on it? Not sure what to do, any help would be appreciated. Thank you.

 

I'd say the master cylinder. Proportioning valve.

 

You need to do something quickly. The truck is dangerous to drive the way it is!

 

Thats what I was thinking too, I’m going to replace it tomorrow, I’ll update the post if it fixes it.

 

No doubt, I was coming home from work today and now the pedals going to the floor almost every time I try it lol, not driving it until that issues gone.

 

Had the same issue on my 97 k1500. I’ve talked to a few techs at Chevy dealership and they all say the piston inside the 1500 master cylinder isn’t big or strong enough. In my case, Replacing the master helped but didn’t fix it completely. I read in a few posts that changing the rear pads and adjusting the shoes every oil change would fix the issue. It’s done the job for me. Brakes still aren’t as stiff as I’d like during hard braking but they work dependably. I’ve also heard you could install a master cyl from a 3500 truck...maybe those have stronger mast Cyl’s.

Hope this helps