Brakes Locked!

bran3b · #1 (**permalink**) 04-12-2002, 08:36 PM

Today while driving in stop and go traffic, I noticed the brakes starting to drag. As I drove further, they got worse. After stopping for a little while, and checking over the car, they freed up. While driving home, at higher speeds, they seemed fine. I came to the conclusion that the heat under the hood got to the point that the brake fluid expanded, causing the brakes to drag. Have any of you had similar problems, if so, how did you fix it?

Bran

ERA535 · #2 (**permalink**) 04-12-2002, 08:54 PM

How many miles on the car?

Is this the only time it has happened?

Don't think the heat under the hood idea is viable.

E-Brake off?

bran3b · #3 (**permalink**) 04-12-2002, 09:41 PM

200 miles or so. Still working out the kinks. The e-brake was off, but my first thought was that it was somehow kinked, or pinched, but the fact that it got worse over time, then better as the car cooled has me stumped. While the car cooled, I did have the e-brake on, so maybe it unkinked it enough to release.

Bran

got snake? · #4 (**permalink**) 04-12-2002, 09:56 PM

hey Brandon,

Glad to hear the car is on the road with the new paintjob!

GS

427sharpe · #5 (**permalink**) 04-12-2002, 10:33 PM

I dont know too many of the details, but it sounds as if a caliper may be beginning to seize or a proportoning valve going bad. Did you leave residual pressure valves in the system? What kind of brake system are you using? What kind of master cylinders, etc? I have seen a caliper locking up cause the same symptoms...it doesn't release the way it should, and takes a little bit of time to let the piston retract into it's bore. I have had this happen when the ring seal inside the piston bore 'flips' or gets kinked. The seal is actually bias cut to help the piston retract, and if it begins to fail it will keep the piston engaged to the rotor. Was the car pulling to one side, or was one end of the car dragging? If both fronts (or rear) were maintaining pressure, I would bet on a e brake misadjusted, or a proportioning valve or master cylinder failure (assuming that you have dual brake master cylinders). A long shot would be a maladjusted bias bar if you are using twin master cylinders...if the jam nuts were loose and let the bias bar shift it will hold pressure against one master or the other. Sounds like you have some brake diagnostics ahead of you! Good luck, and repost details if I can help out at all...

JS · #6 (**permalink**) 04-12-2002, 10:55 PM

First, do you run rubber brake lines or stainless?
Second, has the car sit or is the brake fluid old?

Reason, my friends Posche had been sitting for awhile and the brake fluid actcually cause the rubber brake line to swell from the inside so that fluid would flow to the caliper, but not back once the brake was reliesed. The hotter it got, stop and go traffic, the worse the brakes dragged. (drug?) Kind of similar to clogged arteries around your heart for a comparison.

If you think you brake lines are bad, take one off and try to blow compressed air through it. With the Porsche line, you could barely feel the air coming out it was so bad.

Anyway, the new brake fluids that the racers use won't go bad like regular brake fluid if it sits too long. Going to stainless line will cure it too.

bran3b · #7 (**permalink**) 04-13-2002, 08:03 AM

I do have dual master cylenders, so I will check the proportioning bar first (also cheapest fix). The rubber lines to the front wheels are new, but the fluid might be questionable on quality. All of the parts are new, less than 300 miles.
I will post the results soon. I love this diagnostic stuff

.

Bran

Coloradocobra · #8 (**permalink**) 04-13-2002, 08:38 AM

Hi Brandon,

If you are using the standard e-brake cable setup that Midstates uses, they have a tendency to drag. The way that they anchor the cables on the frame in front of the axle allows the cable to accuate depending on the height of the car. Additionally, because of the way the cables are spread right in back of the e-brake handle, a significant amount of mechanical advantage is lost. It takes a long pull, and even the the brakes do not hold that well. I installed a Lokar handle and cable system that runs full cables all the way to the axles - good grip and never any lock-up. The thing that will really mess you up is if you adjust your rear brakes with the frame on jack stands and the rear axle hanging down. It will darn near bind just by setting it on the ground. It happened to me when I TRIED to help somebody adjust their brakes last summer. I finally got them so they would grap sitting still but we darned near burned them up on a test drive. Another club member in the Denver area had the same problem. The rear brakes would grab when he went over bumps. By the way, the one that I messed up modified the handle so that it was still in the same location and simply installed the Lokar cables. Works like a charm.

Gary

Bob Putnam · #9 (**permalink**) 04-13-2002, 04:55 PM

Make sure that the linkage to each master cylinder allows the m.c. piston to fully retract.

bran3b · #10 (**permalink**) 04-20-2002, 02:17 PM

427Sharp,
Your "longshot" seems to be the answer. I had apparently missajusted the balance bar, which was causing the front brakes to very slowly bleed pressure. While driving in traffic, there wasn't enought time for the pressure to release. I reajusted the bar, and now they feel much better.

Thanks all for the help,
Bran