First post. Thanks for having me.

I believe '91 Accord, manual trans.

After driving for a bit, the front brakes lock up. Replaced the left front caliper, thinking that it was the culprit (thought that it was the only one locking up).

I've read maybe master cylinder, booster, or porportioning valve. Is there a way to narrow it down? Car belongs to a young friend who is strapped for cash, and cannot replace all three.

Again, thanks for the help.

 

Try replacing the others if you can.

 

Young one is back from the used parts yard with a proportioning valve and a master cylinder. We'll see.

Thanks for the reply.

 

Sweet let us know.

 

Make sure there is sufficient free-play at the brake pedal. You should be able to move the pedal at least a 1/4 inch before you feel resistance.

If the pedal can't return to the fully relaxed position, pressure will be retained in the system and the brakes will stay applied, heat up and lock.

In most cases this is caused by the brake switch being kicked out of adjustment or some such foot issue.

P

 

Welcome back P Adams!

 

I have herd of internally collapsed brake lines that will hold the calipers closed with pressure ED

 

This problem is most often caused by an improperly adjusted master cylinder pushrod. As P_Adams suggested, check the pedal freeplay and if needed, adjust the pushrod (which runs from the pedal itself through the booster and actuates the master cylinder piston).