so the car will drive fine but after about 15-20 mins of driving the brake gets so stiff then it will lock up and the car will be stopped with no place to move until they cool off again, any ideas to help this Poor Noob, what should i try (besides just switching to disk haha) thanks in advance
I bet a dollar on bad brake hoses. They get clogged up and the oil can't return to the master cylinder
Start by readjusting the shoes to be a little looser. Insead of dragging when released. It might be that simple.
They actully swell up in the inside, master cylinder has enought pressure to force the fluid through but wheel cylinders can't force it back the other way.
Take it for a drive thats 10 minutes out and 10 minutes back. You want to be back in your yard/garage as the thing gets close to locking up. Jack up a front wheel and verify that the wheel is stiff or locked. Have someone pull back on your brake pedal and hold it back while you check to see if your wheel is still locked up or stiff. If it isn't, your missing a pull back spring from your brake pedal and the piston is being kept past the port in the master cylinder that allows drainback of fluid as heat expands it.
All for wheels or just two? Power brake car? Could be the booster is somehow locking up the brakes. I have had a power booster do some strange things before.
Bad copper washers on your brake hoses will give you the same effect. Make sure they are sealing properly. They can suck air and still not leak.
Another thing to check is what the caliper pistons are made of. If they are stainless steel, then they shouldn't be the problem. If they are a non-metallic material like phenolic or something else that looks like bakelite, then you have problems. Several years ago I had lots of problems like that with a few sets of front calipers with non-metallic pistons that would get stuck in the caliper bores. It only takes a small amount of dirt or fine grit from other parts of the system to make those pistons stick tight enough in the bores that they sometimes don't want to release. Sometimes it comes and goes. I have never run into that problem with stainless steel caliper pistons, only the non-metallic ones. Here is a crazy one for you- I did have a new AutoZone replacement power booster (1978 Cadillac) act up in such a way that it randomly applied the brakes really hard while sitting at a stoplight and wouldn't release. While waiting at a stoplight for several seconds, you would start to hear a sucking sound, feel the brake pedal being pulled down farther than you were holding it, and then you were unable to leave at the green light. The only way to leave the intersection was to shut off the engine, let the vacuum bleed down to release the brakes, then drive away hoping it wouldn't happen again for a while. I had to trade the booster with a bad valve in for another one.
Along with making sure that the pull back spring is working make sure that the push rod is not pushing against the piston in the master cylinder in a way that causes it to cover the bleed back hole in the cylinder. This sometimes happens when the push rod is adjusted wrong or the hole in the piston isn't as deep as the one in the old master cylinder. I've had to crawl under a car and open a bleeder screw before to relieve the pressure so the car could be moved when similar issues happened.
So...what did you find out? Could be a help to other people as its a common issue with many possible causes!
THe residual pressure valve that is inside the port on the master cylinder may be pluged with crud. I had exactly the same thing on a 59 chevy and that is what it was. As the others said the hoses will also cause the same problem.
My 64 Impala acted similar when I replaced the master cylinder recently. My problem was that the rod going from the pedal to the master cylinder was adjusted wrong. I had to back it off a little until there was a little play. Simple fix, but it had been a while since I had swapped a single reservoir master cylinder and I forgot about adjusting the rod.
Bad brake return springs will have that effect too, eventually the springs get weak and the heat of braking cause them to loose tension.
Your master cylinder is under the floor, check to see if the rubber boot is torn and full of dirt and rust, that will cause the piston to not return all the way and not uncover the fluid return port to the reservoir.
I've had this same problem. The brakes on my 52 Pontiac would start to get stiff and drag after I drove the car for a while. I put all new shoes, wheel cylinders, hoses, etc... on it... even rebuilt the master cylinder and it still did it. I also have had to bleed the pressure off to be able to drive the car home. After it sit for a little while, it was fine for a while longer. I re-adjusted the rod going into the master cylinder and the problem was solved. Dave
Thats a good one! I hadn't considered that but its very possible and would be hard to locate as a problem! One to remember....
I would bet it is the rod adjustment on the Master Cylinder. After a short drive, heat from your exhaust (headers ?) next too the master cylinder causes the fluid to expand. The pressure return valve as some hamber mentioned gets past the releif point and pressure forces the brakes cylinders to expand....lock up. The rears don"t due it because of the volume of brake line . front line does because it is shortest and gets all the heat. Bet a dollar thats the cause. It happened to me. Thx v
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