Front Brake lock-up

[JimVette]

What will cause the front brakes only to lock up. I have a good idea but would like other inputs. Let me explain what happened.
I was coming home from a car show Saturday and through my rear mirror I spotted a Camaro pace car coming up behind me in and out of traffic. So I figure he wanted to play, I turn A/C off, radio off (antenna down) and ASR off. Well we never could get side by side but about 50 mph I started to feel a vibration in the steering so I pulled into a side street to stop and see what the problem was. There was a little smoke coming from the drivers front brake. I open the hood and discovered smoke coming from the tire and the front drivers side brake is locked up and it appears the right is also locked but not smoking. I cannot get it to release so I shut it down and am ready to call AAA. I start it up to move it into a parking lot and the brakes are released but in order to get brake pressure I have to pump it several times to stop. I never got a brake warning light and the fluid is normal. By the time I get home the brakes seem to be normal with a little more pedal travel. The ASR is only rear only, the vacuum booster I think should not cause it loose pedal pressure (to the floor). Besides the brake lines colapse or master cyclinder failure I can't think of any else. I have a GM service manual but this problem I could not find in it. '92 ZR1

 

[Vettelt193]

What will cause the front brakes only to lock up. I have a good idea but would like other inputs. Let me explain what happened.
I was coming home from a car show Saturday and through my rear mirror I spotted a Camaro pace car coming up behind me in and out of traffic. So I figure he wanted to play, I turn A/C off, radio off (antenna down) and ASR off. Well we never could get side by side but about 50 mph I started to feel a vibration in the steering so I pulled into a side street to stop and see what the problem was. There was a little smoke coming from the drivers front brake. I open the hood and discovered smoke coming from the tire and the front drivers side brake is locked up and it appears the right is also locked but not smoking. I cannot get it to release so I shut it down and am ready to call AAA. I start it up to move it into a parking lot and the brakes are released but in order to get brake pressure I have to pump it several times to stop. I never got a brake warning light and the fluid is normal. By the time I get home the brakes seem to be normal with a little more pedal travel. The ASR is only rear only, the vacuum booster I think should not cause it loose pedal pressure (to the floor). Besides the brake lines colapse or master cyclinder failure I can't think of any else. I have a GM service manual but this problem I could not find in it. '92 ZR1

how could you tell the other brake was stuck?

If only one brake being a problem I would start with the caliper. take it off and check the travel, make sure it still floats ok on the pins and nothing is rusted or stuck. My guess is the brake didn't slide back to center like it should have and was rubbing on one side only.

The brakes having problems after the brake was stuck makes sense... I am guessing you haven't changed your brake fluid in some time. with all the heat from the brake sticking it would boil any moisture in the lines turning it into air, causing a mushy pedal. Brake fluid loves to suck up our humid florida air, and is really only fully effective for about a year down here. A brake fluid change is necessary at this point no matter what.

 

[G Winter]

Like Vettelt193 said calipers could have stuck to one side, when it came loose you would have the pads quite a distance apart. It would take a couple pumps on the peddle to get them back to where they belong. Take a real good look at both of them you don't want to have to pump brakes on a panic stop.


could there be enough moisture that it would boil and put preasure on the brakes?

 

[JimVette]

You might be right on the pressure loss afterward. I looked at my maintenance book and the last time I changed the fluid was almost 3 years ago. I bought speed bleeders over a year ago with the intention of installing them and changing fluid. The G...D.. storms though have put other to do's at the top of my list and the Vet has done alot of sitting in the garage. Thanks for the input.

 

[aboatguy]

There have been reports of the rubber brake hoses deteriorating and clogging up. Since the Master cylinder pressurizes the brake fluid the caliper

engages normally but the restriction caused by the hose does not allow the caliper to empty and the brake remains engaged.



I do not have personal experience with this phenomenon however, I have read about it many times on different C4 sites and it seems plausible to me.



How old are your rubber brake lines?

 

[JimVette]

I thought of the brake lines, they are original as far as I know. I tried to rock the car using each front wheel and both sides seemed to be locked up but only the left front smoking. I'll order the brake lines anyway because like you I have heard of them collapsing internally trapping pressure and they are old.