My Friend just dropped off his truck asking me to look into it quick since he is actively trying to sell it.
1989 K2500 350TBI ECLB Auto trans, 6-lug truck, vacuum brake booster.
OK, Lots of recent history with this truck and he is just trying to get the front brake to unlock and drive like normal so he can sell it. I'm just looking for quick checks to look into. I cant work on it until tomorrow night so asking for input tonight and tomorrow. If it was my truck I would go about the situation much differently but he needs cash quick so just trying to help him.
Recent history related to brakes: His Pop replaced rear brake lines from the master to the wheel cylinders and also the proportioning valve right next to the master, then tried to bleed the rear brake lines. He said the left rear couldn't bleed at all. He got the proportioning valve lock-open tool so he could bleed the rear, still didn't quite work apparently. I looked into the master and the rear reservoir is fresh and clean and the front is dirty.
He told me to not mess with the rear, its 'good enough' unfortunately. I'll still bleed that rear properly because its somebody else's safety. But that's just showing where his mind is at right now.
OK, history done, now onto the problem that he asked me to fix: This is a new problem since the rear brake lines and proportioning valve were replaced. (and fronts probably haven't been bleed). When you step on the brakes to shift from park to drive or reverse and try to go, the front drivers side is LOCKED SOLID. After he left, I tried to move it in front of my garage and it just spun the rear tires in either Drive or Reverse, non-directional. Then lightly tap the brake pedal dozen times and it drives like normal. Come to another stop like sitting at a stop light, same thing... tap it a dozen times and drives like normal.
My first step was going to be just bleed the whole system properly tomorrow but please any other ideas welcome!
The front rubber 'looks' ok but that would be my 2nd suggestion to him to replace. But ballooned rubber wouldn't let loose by tapping the brake repeatedly, right? Those just hold pressure and gets the rotor hot from my experience. These rotors weren't hot when he got here (30 min drive)
I've never replaced a proportioning valve or had to use a special tool to bleed it, could something be out of adjustment with it?
The left front was the worst but it could very well be both fronts locked up.