i got a 1984 toyota truck 4x4 that i have built into a trail buggy and i have replaced the brakes master cylinder, pads, shoes, cailper, and wheel cylinders and it still won’t stop. you can hit the brakes and maybe 1 for every 4 or 5 times it will stop. the rest it just goes the the floor. if you put it on a incline or decline there is no brakes what is wrong with it i am at my witts end… BTW it is a stock drivetrain and i have bled them too know end and there is no air in it
A lot of “new” parts these days are bad off the shelf. I’d suspect the master cyl you put on there might be no good.
Hopefully you’re also certain that you used the right brake fluid.
If the flexible brake lines are original I’d also replace those - If bad those would tend to just produce a soft pedal moreso than unpredictable pedal to the floor, but either way its a good idea to replace them.
I concur with Cig’s suggestions. But I have a question: what are you rumming for wheels and tires?
If when converting this to a trail buggy you went with huge tires, you’ve dramatically increased the rotating inertia and put it well away from the axle’s axis, both of which will require substantial brake system upgrades.
To illustrate, try spinning the wheel on a 700C (road) bicycle wheel, and stop it with your fingers. Now try it with a mountainbike wheel. You’ll find that the mountainbike wheel is far harder to stop. That’s solely because of the increase in inertia due to the heavier tire. Multiply that difference by thousands and you’ll get the idea.
Dont be so sure there is no air. The symptoms of the peddle you describe, and the intermittent nature of when they do operate, suggest very strongly that there is still a major air bubble trapped in the lines or a cylinder somewhere. It could be, as ciggy sugests that a defective cylinder is leaking internally, even though new, I have seen this before on my 85 toy and it took three brand new masters before I got one that worked. Have you tried taking it in for a power bleed? this will positively eliminate the possibility of air. TSM’s comments are enlightening too, and must be considered.
Did you bench bleed the master cylinder before installing? A very important step.