I have a problem with my brakes, the back drums lock up when ever its wet or cold which makes it scary in snow. I changed wheel cylinders brand new line and hoses, master cylinder and new calipers/pads and shoes. It still feels as though only the back are working and the fronts barely work, my pedal is soft and almost goes all the way to the floor, could this be bad a proportioning valve/combination valve? or a bad brake booster. If i hit the petal multiple times it gets harder. before I start the truck there nice and hard as well, but as soon as I start it they get really soft. I have bled the lines multiple times with no air coming out. Please someone help this is very bad with the snow coming and my truck is my dd

 

Booster maybe

 

any leaks? i had a car in the shop a few months ago that had a right rear brake that was destroyed. replaced everything worked fine i thought on the test drive. got it back it the shop to check it all out and the wheel was locked up. it wouldnt release after the pedal was pushed. turned out that the rubber hose had deteriorated inside itseld and was acting like a 1 way valve. replace those and brakes work like new. whether or not this is your problem you might look into it. those arnt very expensive.

it was an instant brake lock-up situation in the back.

 

I will give it a look but I dont think thats it cause ive put all brand new hoses and new brake fluid, There is a switch on my driver side fender that connects to the vaccum lines and it has a broken connector so i stuck a screw in the hose for now. Does anyone know if this switch can affect my brake booster some how? I deffinitly have vaccum pressure though

 

No, the switch is just an idiot light thing. There's actually a load sensing valve in the back, if the lever is just hanging in the back the rear brakes can apply harshly.


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If your pedal is spongy and travels more then 2 inches then you could have air in the master cylinder or the master cylinder front brake piston has a bad oring or the cylinder the piston it rides in is worn out. you can loose all the rear brake fluid and still have an "adequate" pedal in a front to rear system. I say this because I have driven many old trucks that the customer never complained about the brake pedal, just the brake light... I have fixed a 2001 ram from another shop that put the calipers on the wrong side, the bleed screws were on the bottom it cause a pedal like you discribed.. The other shop wanted to blame it on the hydro boost.... I have seen collapse brake hoses 3 times this year, but the pedal is hard and it pulls if its a front hose or grabs if its a rear hose.. If the rear brakes are way out of adjustment the pedal will be a little soft (under 2 inches of travel) and rear brakes will be grabby cold.. Why did you replace the hoses? Was it this way before you touched it? If it was its probably the master cylinder.

Good luck

 

I replaced the hosses when i bought the truck a year ago and this just started happening this winter. Ive bled the lines and no air come out and the master cylinder is new from a few days ago. Rear brakes are adjusted and now leaks. There is probly more than 2in of travel in the brake pedal before it starts braking almost all the way to the floor. Im leaning towardds a bad brake booster or proportional valve. Maybe even my rear abs?

 

Do the fronts gravity bleed? If they do and the proportioning valve doesn't leak then the proportioning valve is fine. Pedal to master cylinder thru the brake Brake booster is a mechanical link.. If the brake booster is bad you will have no assist and your pedal will be hard and hard to stop the truck. Search online for a cut away view of a brake booster to fully understand the relationship between the pedal and the master cylinder. It's a bad master, air or leak.

 

i know every rear drum vehicle i have ever driven had back brakes that locked up for the first few applications after i drove in rain/snow and parked it. i always thought it must have been surface rust on the inside of the drum

 

Adjust them mechanicaldiesel did you get ur brakes fixed?