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2006 Pacifica intermittent brake failure

This is the first time I’ve attempted to utilize a forum so here goes…
My daughter has experienced what she describes as total brake failure (once at low speed and once at highway speed!) 3 weeks apart. Another symptom that I should mention that happened both times is that the engine began idling alternately high then low then high, etc, along with a “jumpy” speedometer. After the first occurrence, it was towed to an accredited garage where it was diagnosed as two unrelated issues: 1) a kinked brake line and caliper out of place, and 2) a communication glitch between the alternator and transmission. I consented to repairing both - replaced the alternator and flushed brake fluid (they said it was dark-ish), unkinked the brake link and addressed the out of place caliper. All seemed well for 3 weeks then the second occurrence happened. Had it towed back to same garage where they have been unable to diagnose the problem since they cannot seem to repeat the failure. All they found was a PVC valve to replace.
It has been suggested by others with some mechanical knowledge but no one who has actually looked at the car, that it might be a failing brake booster. When the service manager called to tell me that they haven’t found the problem, I suggested they consider the brake booster. He called again to say that they could replace the brake booster and master cylinder if I want (for $500!) but that they still are unable to observe the brake failure or weird loud engine sound. I am willing to do the repair out of self defense but I am reluctant to do so since the last diagnosis was not correct (so I wasted that $475 !). Twice now my 8-month pregnant daughter got away without injury however I am afraid to put her back behind the wheel without knowing for sure that the issue has been identified and corrected.
What do you suppose the problem is and how can it be forced to manifest for the mechanic to observe?

A bad brake booster would not result in brake failure. It would mean, however, that the brake pedal is much harder to depress than usual–i.e.–a lot more force would be necessary to apply the brakes. A bad brake booster could cause erratic engine performance, however, due to vacuum issues.
A bad master cylinder would usually mean that the brake pedal went all the way to the floor, with no effect on the brakes.

Could you clarify the exact nature of the “brake failure” for us?
:thinking:

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She described it as applying the brake which was hard to push and although the car did slow down some, it was not nearly enough stopping power to control the vehicle. The first time she turned quickly into a parking lot and it eventually came to a stop. The second time she applied the emergency brake which slowed it down then she scraped it along the retaining wall and slammed it into park to stop it. I am told that the diagnosing mechanic has been driving the car around and unable to repeat this condition. Does that help?

When you say “erratic engine performance”, could that explain the loud-normal-loud/high-low-high “idle” engine sound?

How experienced of a driver is your daughter? What you describe could be simply that the engine stalled, which wouldn’t be surprising if it’s not idling correctly.

She is 28 and lives in Dallas, Texas. I’ll ask her if she remembers having to turn off the engine once the car stopped either time.

That sure seems like the symptom of a failing vacuum brake booster. The “hard pedal” but the car still slows is a big symptom. The erratic idle can be created by a big air leak in the booster that the engine is trying to control. It is odd that it is intermittent but it might be worth it to replace the booster now. It certainly won’t get better, it will only get worse. Good Luck to you and your daughter and new grandchild.

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If the car had a kinked brake line and out of place calipers (my guess, installed on the wrong side) You did not waste the $475. Those things needed to be fixed. The fact that the poor stopping re-occurred just means that you had more than one problem. I like the engine stalling suggestion. Another thing I have seen happen is the driver getting their left foot trapper under the brake pedal and pressing down with the right foot but not being able to stop the car.

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A sticky PCV valve can cause an engine to run rough, and could cause a low vacuum which could affect brake booster when using brakes more than once, like driving in stop and go traffic.

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Thank you all for your input. I didn’t hear anything from the service manager yesterday and I was putting off calling them until I got some Good Orderly Direction from y’all.

Based on your feedback, I am leaning towards authorizing the Brake Booster replacement and I already had them to replace the PCV part. Do you think I need to let them also replace the master cylinder, too?

When we spoke last week, Ii was told they were unable to reproduce the failure but when I specifically asked about the possibility of the culprit being the Brake Booster, he came back and said they read something on a “Chrysler mechanics blog” (or similar) which spoke to replacing BOTH brake booster AND master cylinder.

I will gladly spend the $$ if its a matter of risking the safety of my daughter and grandchild if there’s any doubt among The Experts (YOU!) however if you feel strongly that the PCV & Brake Booster is all that’s needed, I’ll go with that and not include replacing the Master Cylinder.
Please advise.

Considering they are already working in that area, might just make sense to do the master, too.

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One place in addition to CarTalk that’s helped me with my Chrysler minivans has been allpar. com. They have a discussion group devoted to minivans and Pacifica, with some very experienced people.

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Thank you, Shanonia.

The idle rpm changing at random could be caused either by a faulty brake booster or the pcv valve, so it seems like you and the shop are on the right track for that. The brakes are the bigger problem though. It’s good the shop is willing to let one of the staff drive the car to see if it ever happens to them. You might just have to let them keep doing that for a while, and your daughter secures alternate transport in the meantime, maybe renting a car. If I had this problem the first thing I’d do is test the brake booster with a hand-held vacuum pump to make sure it hold vacuum to 20 in hg, steady for at least 5 minutes. And I’d remove & visually inspect the hose between the intake manifold and the booster on a well lighted work bench for problems like the rubber is cracking, etc.

I suggest you don’t try to address this problem by making a guess and replacing that part. You’ll likely run out of money before you run out of guesses. Brake master cylinders rarely fail in an intermittent way. The problem with them usually shows up as the brake pedal slowing going to the floor as you press on the brake pedal. Which always happens when you press on the brake pedal firmly for a period of time, not just once in a while. Here’s some things that need to be ruled out before going on a parts replacement spree

  • does brake booster hold vacuum?
  • is brake fluid in good condition and at the correct level?
  • has the brake fluid been bled of air per the Chrysler spec procedure? This often requires special Chrysler equipment if the vehicle has ABS, which has its own bleeding procedure.
  • are there any diagnostic codes stored for the brakes or the ABS system? again special Chrysler equipment is required.
  • is there an explanation for how the caliper got out of place? likewise for how the brake line got kinked?
  • have all four wheel’s brake systems been disassembled and inspected?
  • has the brake pedal ass’y been closely examined for parts breakage, cotter pin fell out, carpet interference?
  • have the brakes ever been bled by someone who isn’t familiar with the Chrysler ABS system? An incorrect bleeding method can cause contaminated brake fluid to be pushed into the ABS unit.
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