mtywty

I'm having a hard time diagnosing my issue. Basically I drive all day everywhere (sales), when i have to 'jump' on the brakes quickly the pedal is very hard and does not stop for about 1 second or 2. Then the brakes engage. Truck is a '99 k1500 classic body style. I've had it at several shops. One Chevrolet dealer and one Ford (i have a buddy there). Both tell me the brakes are fine and within "Spec". My wife's 05 tahoe and my 94 1/2 ton do not have this problem and have similar setups. Any suggestions? Sorry for the long read and I know its not LS but I'm lost and everyone here has always had an opinion good or bad.

I have replaced everything, master, booster, all pads front and back, rotors, rebuilt rear brakes, relathed rear shoes, wheel cylinders and bled about 2 bottles through the system, the big ones.

Josh

Brakemotive

iTrader: (73)

Do you know what brake pads you are running? If they are a fleet type or sever duty pad they may not have the cold friction characteristics you're after. If the system is sound mechanically and bled properly you shouldn't have any issues with initial pad bite. A stiff pedal is usually a sign of a bad booster - if you haven't yet I would suggest inspecting the vacuum line to the booster as well as the grommets etc (anything rubber) for proper seal. The rubber components will dry rot inevitable and rob you of the vacuum needed to properly operate the booster. (assuming you have a vacuum booster on there and not a hydraulic one)

Also, do you tow a load around with it? Or in the bed?

Jon87transam

iTrader: (1)

i own a C2500 suburban (in sig) and like yourself, have had brake trouble since in owned it which is almost 2 years now. although i have hydroboost instead of traditional vacuum brakes, but never could get the truck to stop. idk if your also having a stopping distance problem or not, but i wouldn't be suprised if your problem may lie in the proportioning valve, which is built onto the abs pump on the driver side inner fender. my truck had a similar issue on hard stops, but i also would just smoke the front brakes, blowing stop lights, or have to head for the ditch. i did almost everything you have, minus the master/booster replacement, and i also have the 13x3 1/2 drums on the back, which are the biggest gm used in those days even with a dually (14 bolt full floater rear end). they were adjusted so tight at one point i couldn't hardly turn the rear wheels with them in the air. to not get into a really long story here, i had enough, and i disconnected and removed the entire abs pump, and to my suprise (not really) all the lines into the system had different fittings and such. so i cut them all back about an inch, (there are 5 lines, 1 front input-2 front output, 1 rear input-1 rear output) and i "T" the front lines together, i used a JEGS adjustable proportioning valve for the rear, and also ran from that into a 2lb residule valve to keep just a small amount of pressure on the rear, about enough to keep the wheel cylinders slightly loaded. immediate improvement! that fixed all my issues that i know of. i now have to feather my brakes on hard stops to keep from lock-up, but i'm ok with that, and i have full adjustment for my front/rear bias. before, i really didn't need abs, because it wouldn't have locked a wheel if it had to, i tried (with the abs un-plugged). idk if this would help your paticular situation, but it sure helped mine. if you want some pics just let me know. btw, total cost was around $100.

Wesmanw02

iTrader: (4)

My friend has a '95 Blazer with this exact problem. Hard pedal when brakes are first applied, resulting in delayed engagement.

After doing a complete brake service, changing the master, and replacing the booster, my diagnosis has come down to there being a restriction in the system. It seems that there must be a fluid restriction somewhere, most likely in the ABS/Combo unit. One day when we have some free time we are going to bypass the ABS block and see if it eliminates the problem.