Help! I can't stop!

[ckhd]

No, this is not about any addictions, except maybe '67-72 Chevy addictions!

I have brake issues. 1/2-ton 4 wheel drive. Brakes work great first 1-4 times, but then I might as well be sticking my foot out on the ground and trying to stop Flintstone style.

Things that have been done:
2) new master cylinders
2) new brake boosters
2) new check valves (the vacuum one in the brake booster - held vacuum for three days)
"professional" reworking all four corners (Previous owner had this done real recently, haven't checked it yet)
Bled, bled, bled, bled, bled, and then for good measure, bled some more.

I haven't touched them yet. The previous owner told me all this when we were negotiating price. Any ideas?

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Bowen
'68 K20 fleet
'69 K10 swb fleet
'72 C10 lwb step
'72 K10 Suburban



[This message has been edited by ckhd (edited May 13, 2002).]

[pierce]

The previous owner may not be lying but he may not be telling the whole truth like it was new 10 yrs ago...The previous owner of mine told me that he put on a new MC. I couldn't get the back drums to pump up. I put a new MC on and it worked fine.

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72 Chevy Blazer
69 GMC Longhorn
37 Chevy Coupe
pics at http://home.fuse.net/pierce
Cincinnati, OH

[Mongo]

Hmmm, It looks like you replaced everything but the proportioning valve. Mabey give that a try. Other thant that you have scratching my head too.

[This message has been edited by Mongo (edited May 13, 2002).]

[ckhd]

Pierce, the previous owner is a local guy and I kinda know him. A friend of mine knows him pretty well, and the guy has been completely honest and forward with me on the deal and I have no reason to think that he didn't do all the stuff he told me. Besides, the MC looks new (and so does the brake booster). I have gotten MCs that weren't rebuilt right, but I wonder because it was doing this with his original MC, then with two replacements.

I was kinda thinking about the proportioning valve. The only things that haven't been given attention that I can think of is that and the rubber lines. I thought that maybe the lines were balooning, but it seems that they would baloon every time, not just after a few uses. I don't know, I've never had the rubber lines baloon...

I do wonder about the "professional" that did the corners. I know some of the "professionals" in this town and I could crap a better brake man -- like the "professional" that did the rear drums on my brother's '78 F@#d. Went 200 miles, and one of the shoes cut the drum in two! That's some good brake repairs! Or the "professional" that did my brothers front disks on his '92 K2500, and cross threaded the caliper bolt, and instead of backing it out and putting it in right, he took an impact wrench and made a whole new set of threads! That "professional" got to buy a new caliper once we found out what he did.

Anyway, anyone have any other ideas? Anyone know where can I get a proportioning valve (front disks, 4-wheel drive)?

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Bowen
'68 K20 fleet
'69 K10 swb fleet
'72 C10 lwb step
'72 K10 Suburban

[bigvinnie]

Need a better description of the problem... you say they work great the first few times, but then what? Does the pedal get hard to depress, does it go to all the way to the floor, etc..... knowing the symptoms would make it easier to diagnose the problem...

[Blue68]

Take a look at your brake lines. Are they witin an inch or two of your exhaust? Running headers? If you get the fluid above about 500 degrees, you'll boil the fluid and kiss your brakes goodbye. You need a couple of inches distance at best.

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'68 C-10 LWB, '98 Z-71 350 w/accessories (Serpentine), Edelbrock Performer, Edelbrock 1405 (600cfm) carb, GM HEI, CompCam Extreme 4x4 roller cam, Thorley Headers, Carter Electric Fuel Pump, Vintage Air, 700r4, 3.73, disc brakes and power steering upgrades.


Way too much money and time..But it's a hobby.