kcochran

Hello,

I know that brake issues have been covered thousands of times before, but I'd like some specific advice before ordering parts.

I bought a 1980 last week, and need to get it to pass safety this week. It had a minor drag on the front left caliper, the rim would get a little warm and under hard braking (as in a lot harder than you'd have in town) it would pull right as if the left caliper wasn't grabbing as hard. It got worse throughout the week / 300km.

I ordered brake lines as they are pretty hard, and while driving home the brake light came on and the brake pedal dropped to the floor. To the floor barely holds the car at a stop sign, but if you try to drive it through the floor like hulk you can get the car to stop with some downshift assist.

Would I be safe in guessing the left caliper got too hot and burned out a seal? New caliper for that corner and new hoses all around, a solid bleeding and should be good to go? Anything else I should investigate now while ordering parts (ie prop valve, MC) so I don't have another week of down time?

SIXFOOTER

With that kind of thing happening I would not make any assumptions.
First, look for leaks, thats an obvious way to locate some problems.
What does the brake fluid look like? If its cloudy it has moisture in it which could cause all the symptoms you described..

The light came on because one branch of the brakes is failing, causing the proportioning valve piston to shift.

If there is doubt, replace the soft lines. Then I would pull, inspect the calipers, rebuild or replace as necessary. Flush and refill the system and bleed all 4 branches. You may have to play around with the proportioning block to get it to reset, there is a procedure in the manual for that.
You have at least 1 issue and maybe more in there. All this is quite doable in a weekend.

Good Luck and repost with pics, questions and results

BlackC3vette

When the brake light came on, pedal to floor - was the car still pulling to one side? If there are no leaks in the system and the MC is full, you could have an internal leak in the master. But a bad master would cause all wheels to perform poorly due to not enough pressure in the system. You can also jack up all four and rotate each wheel one at a time and have somebody step on the brake to see if the wheel stops rotating.

kcochran

I took it all apart, the front left that seemed to be sticking was a mess of brake dust and was definitely leaking. Swapping the front lines, calipers, rotors (original at 90,000km, but the one looks pretty torched) and pads. Hopefully that solves it.

The car was stopping straight and the rears were still (kind of) functional so I think the MC and prop valve did their function properly after a front caliper went through a total melt down. I'll report when the parts come in! Brake fluid by the way looked more like old engine oil than brake fluid. Thick and BLACK.

Easy Mike

Probably not. What is more likely is that the left front pistons stuck with the pads in full contact with the rotor. Hence the heat.

Possibly not.

My advice is not to order any parts until you have R&Red the entire system, front and rear, and determined what you actually need.

See above.

Rotors seldom fail and thousands of them stay within GM specifications their entire lives. Check yours before deciding whether they need to be replaced. No sense buying rotors if you do not need them.

BOOT77

From stuff I've read sometimes the rubber line brakes down and doesn't let the caliper release fully.

kcochran

new calipers, pads and lines did it. The pad on the one had basically dissolved from heat and brake fluid, came out in 5 pieces. Car stops straight and hard, light cleared after a hard press on the pedal. Looks like all is well!