I have an 85' pickup and when I bought it I noticed that the brake pedal had to be pushed really far before it engaged, way after the brake lights had come on and once it engaged, it was really touchy to where if I pressed any harder, the truck would throw you forward like I just ran into something and in the rain makes me dangerously slide to a stop. It's very scary to drive in the rain. I have to try not to slide just to come to a stop and can't stop fast enough before the brakes lock up. My 4runner was not like this at all so I'm wondering what's wrong. The proportioning valve was also taken off the back because they said it would always lock the back tires. What's strange is that on a hill, the pedal holds pressure just fine and doesn't bleed to the floor like it feels like it's going to.

Do I need new pads all around and to bleed the brake system? Or could this be a brake master cylinder going bad?

 

Unless the proportioning valve wasn't functioning, you are more likely to lock up the rear wheels without it, not with. It's not a true statement to say it causes the rear to lock up, infact it's designed to do the opposite. If a proper by-pass of the valve was achieved, you will be able to lock the rear wheels, before the front, much more easily.

If your brake booster is failing you will have to push the brake pedal further to the floor to get the brakes to grab. Or pump the pedal a few times to get the pressure up.

I don't think you'd be able to lock the brakes up so easily with air in the lines, or with a bad master cylinder. Nor is it too likely to be a brake pad/shoe issue, unless they are so far gone that they need to go.

 

I have an 85 that i bought with similar issues and found out the previous owner had v6 calipers that by the time i took them off were ruined and they were on 4cyl rotors. Id take the assemblies apart at each wheel starting with the front.

 

Everything is stock brake stuff. I think all they've done is replace the pads.

 

They might need an adjustment. Try pulling on the parking brake part way and see if they catch quicker. If they do then the rear brakes probably need an adjustment and the automatic adjusters might not be working. It could also have air in the lines.

 

Doing that didn't change anything. I'm thinking about just replacing the brake master cylinder. It's rusty anyways and the level sensor wires have broken off. I bled the brakes and no air came out, just a steady stream of brake fluid. Same problems too. I'm thinking the master cylinder isn't distributing pressure like it should.