Questions and Answers
Self Applying Brakes
Q. I have a question about a very stubborn problem with my 1981 toyota 2X4 pickup R-22 engine. The front brakes locked up on me so I changed out the front calipers for new ones with new pads. I thought this would solve the problem.
The brakes still lock after about 15 minutes of driving time. I can drive the car a little further by bleeding off the pressure from each front bleed nipple, however it returns even if I do not use the brakes in about 10-15 minutes.
I am wondering about 2 parts here. One is the pressure regulating valve. It seems that this would only make the rear brakes lock if malfunctioning? Secondly, the master cylinder. There must be a pressure release in this somewhere?
There is a third part, the vacuum assist, which if malfunctioning, might somehow keep adding pressure as the engine runs until it locks the brakes?
Anyway, thank you for any info you might be able to share with someone stranded on a tropical island....
Regards,
KollaA. It was always my dream to be on a tropical island with a hot drink and a cold women.... wait... uh... let me think about this and get back to you.
Anyway, you have a rather unique problem here. I read your question and thought about it for quite a while and I have never seen this particular problem before. I called a friend of mine who's been a Toyota technician for the last 27 years and he was stumped as well. After talking it over, (and killing a six pack) we kind of drew a blank. To our way of thinking, the only thing that could conceivably add pressure to a brake system would be the vacuum booster. All the other possibilites would hold pressure after applying the brakes.
In general, when you bleed the brake system, you should bleed the front and rear brakes to equalize the pressure on both sides of the proportioning valve.
You got me on this one. Maybe if you posted this question on my message boards, someone will have some suggestions for you.
