front brake help...

[westong]

Working on a 1972 K10......since i got the truck the front brakes have been poor.realy poor actually...when on gravel or a hard stop on pavement the rear wheels lock up and it feels like the front are weak. I replaced both front calipers and still no luck, when bleeding i have good fluid coming out with no air in all 4 corners and can get the front to lock up when tryig to turn by hand. I have bleed all 4 five times with no diffrence....old calipers acted the same way...any ideas.....thanks

[BMERDOC]

Do you think the rear brakes need to be loosened up? Are they touchy to lock up? What does the friction material on the front pads look like? Do the front rotors look glazed?

[michael bustamante]

I had the same problem in myk5 4wd blazer. Loosening the rear by hand helped a litlle but I had to replace the prop valve

[westong]

The breaks only work with your foot to the floor...both rear breaks lock up pretty easy ....the front rotors are somewhat rusty but both front pads are replaced. ....

[Gumby]

all to common on many GM boards, I struggled with that for a long time in my Firebird. I replaced nearly every part till the last thing I did was toss some cheap $15 pads on it.

and I had brakes, as if the fancy high dollar pads I had on there, that still looked new would not grip at all till you got real hard on the pedal. [ who changes pads that look new, used a grinder to give them a fresh surface, no help ]

a good 5 years of crappy brakes and spending money yearly to try something different.

my long strugle
http://www.thirdgen.org/techboard/br...i-do-keep.html

[BMERDOC]

If you have long pedal travel and the rear lock up first I'd say the rear cup in the master cylinder is bad. The front reservoir is for the rear drums and the rear is for the front discs. The cup in the master for the front brakes is bad. This is the fundamental reason for a split system so that all the brakes aren't lost if one segment loses pressure. Replace the master cylinder. If the rears still like to lock up somewhat prematurely then loosen up on the rear adjustment until they do. You should be able to spin them and have the drum still want to spin on its own for almost a full revolution. Its an old tried and true method for adjusting the rears.

[tcoop68]

You might check your proportioning valve that's the valve close to your master cylinder it's what regulates pressure to front and rear, you might also check and make sure you don't have a crimped line. Hope you figure it out. Coop

[WIDESIDE72]

Sounds like a mc and/ or prop valve to me.

[WIDESIDE72]

Fyi its "brakes" not "breaks" but i guess you figured that out, since you used the correct spelling in the thread. I know that you cant edit the title after posting. Im not an English teacher but have done some technical writing in the past and its a per peeve! (Although I have even "fat fingered" a post title myself in the past!)