Question I have a 1989 dodge diplomat. I have changed both front brake calipers, a brake lin on front driver side and brake master cylinder, and also proportion valve. I had bench bled the master cylinder before i installed it. I bled the brake system with engine off, rear pass, rear driver, front pass, front driver. i turned the engine and press the brakes and had pressure then pedal slowly went down. i drove the vehicle and had to pump the brakes a few times and pedal goes all the way down for brakes to stop vehicle. I then changed the brake booster and bled brakes again in same sequence. the brakes was still doing the same thing. the pedal has pressure when engine off. when engine is on, i have to pump brakes a few times for brakes to have pressure and pedal goes almost all the way down. Can u please tell me what i am doing wrong or what i have to do to fix this problem.
Answer Hi Ryan,
Assuming that you are not loosing brake fluid (correct?), and although you changed the brake power booster, what you describe is consistent with there not being sufficient vacuum to the booster for it to operate properly. So I would check the vacuum hose, its connections at the booster and the intake manifold, and the other vacuum lines that it shares with the heater system (a small diameter hose that goes through the firewall to the ac/heater control panel and to the cruise control. A leak in any of those lines will impact the power brake booster function in the manner that you describe.
Let me know what you find.
Thanks so much for the rating and nomination.
Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.
I answer questions seven days a week and respond to you in about 30 minutes. "Maxed Out" means I am answering another question or briefly unavailable so try again later.
I have do-it-yourself experience (50+ years) and a library of 100 1982-2012 Chrysler factory shop manuals and 20 multi-manual Chrysler Corp. CD's.
I was voted "Top expert" from 2010-2015 here at AllExperts, and have answered 20,000+ questions.
Five decades as a 'do-it-yourselfer' on domestic and imported cars
Organizations Yahoo Autos Group called The Chrysler Lebaron Club (co-moderator)
Education/Credentials Degrees in Physics/bruised knuckles.
Awards and Honors "Top expert" of 2010, 2011, 2012, 2013, 2014, and 2015 here at Allexperts.
Quickest "average response time" at Allexperts (currently no. 1).