I have a 1995 Blazer with major brake problems. If you use the brakes very lightly, they seem to work ok... the pedal feels normal and the truck comes to a stop. But as soon as you press on the hard, like for a panic stop, the pedal is super hard and it takes a bit to come to a stop. When presses hard, it feels like there is no vacuum boost. This problem has been going on for a while, and I have changed the following parts:

master cylinder, twice
vacuum booster, twice
removed ABS system
proportioning valve
front calipers
some brake lines that were connected to the parts above
bled brakes, twice

Any ideas?
Oh yeah, the brake light comes on as soon as you step on the brakes for the first time and stays on until you turn it the truck off.

 

You should have a combination valve (metering and proportioning) there and not just a proportioning valve in your system, if I am correct in believing your blazer has rear drum brakes.

 

Sounds like the combination valve is really dirty. Perhaps removing it and giving it a good cleaning by using brake cleaner through it is in order, although I have not heard of this before....but you do have a '95 and that is the first year of the new body style and a hybrid year.

Good luck with it.....I sold my '95 a long time ago.

 

The valve was replaced, and it did the exact same thing before and after it was replaced. Same thing with all the other parts listed. Not one of them made a difference, and I did the MC and Booster twice just in case they were defective out of the box.

 

Wow just going to toss this out how about a new plenum gasket and hose to the booster.

 

That brake light is coming on for a reason. The pressure is falling off on one side of the valve allowing the other side to push the valve over and complete the electrical circuit and turn on the light. As you have taken the abs system out of the equation. by removing it I think you need to be sure that the correct lines are coming from the master cylinder to the combination valve. In other words the line from the master cylinder that goes to the combination valve from the disc brake side of the master cylinder goes to the front brakes only. Same for the drum brake side of the master cylinder. You also need to be sure that the drum brake side of the master cylinder has a residual pressure check valve in its system.

 

Did the ABS fail and that was the reason for removing it? Not sure if the vehicle computer is capable of setting the BRAKE lite to on if it does not sense the presence of the ABS.

I think Cancy Pell might be on to something.....

 

The ABS was removed because it was suspected to have something to do with the pedal issue... and it was annoying.

 

Interesting, thanks... I will have to look into that.

 

When you bled did you have trouble getting fluid from ether the front or the back?