98runner210

When my truck is cold (sitting for a long time) the brake pedal is very hard to push for the first 4-5 minutes. It is like stepping on a brick and very hard to stop the truck. When warm, it brakes normally unless I have to slam on the brakes. If i hit the brakes, the pedal is hard then gradually goes down. It doesn't even stop hard enough to get the ABS to kick in. It has new pads and rotors with new shoes in the back. Someone kept saying pads or something but I don't think that would create a hard pedal. Any ideas?

ninjarunner

flush the fluid, mines does it for like 30 seconds, you might have quite alot of water in it. brake fluid absorbs water.... just a thought

jason191918

Sounds like a MC.

98runner210

brake fluid has been flushed

GSGALLANT

Check your brake booster check valve (It's on the vacuum line... a couple of feet away from the booster.) It may be sticking closed when it's cold, which would prevent vacuum to get to your booster and would cause the exact same symptoms you're describing. I replaced mine with one from the junkyard, and although it still does it slightly for the first couple of brake pumps when it's really cold outside, it is much better than it was with my old check valve.

98runner210

is there any way to check or test it?

GSGALLANT

Yeah... take the check valve out and replace it with a hose nipple of the same size. If the problem goes away, the check valve is your culprit. If it doesn't go away, at least you'll know that's it's not your problem.

Be aware that with the check valve removed, you'll have no reserve power brake assist in the event that your truck stalls while you're driving (the check valve allows you an assisted pump of the brakes even after your truck shuts off).