Brand: Cause of brake system failure requires sleuthing

  • Article by: PAUL BRAND
  • July 5, 2013 - 1:27 PM

Q: I was driving my 2008 Ford Escape Hybrid in rush-hour traffic when my brake system failed. The ABS warning light and a message on the information panel told me to check the brake system. When this happened I lost most of my stopping power although I had some braking left by pushing hard on the pedal. At my garage, the technician inspected the vehicle and read the failure codes — C1479 and C1481, which read “plausible brake pressure incorrect.” They were unable to re-create the failure mode and the vehicle worked flawlessly in their tests.

The Ford dealer told me that the advice from Ford with these failure codes is to check for a brake fluid leak and, absent one, to replace the hydraulic control unit. There was no brake fluid leak. I have now cautiously driven the vehicle for several weeks and everything has worked perfectly every time, including the braking system. The cost to replace the hydraulic control unit exceeds $4,000. If this was your vehicle, what would you do?

A: That’s a tough question. My ALLDATA automotive database confirms what the dealer told you. Diagnostic Trouble Codes C1479 and C1481 refer to left rear and right rear “brake pressure control plausibility failure,” respectively. Ford’s service recommendation is to check the hydraulic system for leaks, and if no leaks, replace the hydraulic control unit. The heavy pedal pressure required during this event indicates the brake system was in the “manual mode,” which is basically a fail safe mode to ensure the brake system will still stop the vehicle.

Here’s what I would do. Flush and bleed the entire brake system to remove any moisture and debris and fill the system with fresh DOT 3 brake fluid. Bleeding this system requires a special process done with a pressure bleeder and scan tool. Your Ford dealer might be the best choice for this.

Check the condition of rear brake pads. Due to the regenerative hybrid braking applied to the front wheels, the rear pads will wear roughly twice as quickly as the fronts. As the pads wear, more brake fluid is drawn into the system, perhaps trapping debris or air in the rear hydraulics.

If it were my vehicle and no problems were found during the inspection and bleed process, I’d be inclined to drive the vehicle cautiously until one of two things occurs — the brake issue recurs or, hopefully, it doesn’t and your confidence in the brakes returns. Remember, even in the manual mode, the brakes still work and will still stop the vehicle.

Q: My 1991 Dodge Caravan with a 3.0-liter V6 and 260,195 miles is acting like a cylinder or two are cutting out or missing. When the vehicle accelerates harder into passing gear, it runs OK. It will run without a problem for a week or more and then start missing again. It has new plugs and fuel filters.

A: With that many miles on the vehicle, start with a cylinder balance test — the electronic version of a compression test. Low compression may be a big part of this issue. This same test will also evaluate performance of the ignition system and coil. A check for fault codes might turn up a clue as well, although this vehicle has an early OBD (onboard diagnostics) I engine management system with limited self-diagnostics.

And don’t overlook low fuel pressure as a possible intermittent cause. A weak pump or clogged sock filter might be a factor.

Q: I have Grandpa’s big 1996 Buick Park Avenue and a 2012 Ford Focus. I know today’s cars are much safer than yesterday’s, but settle an argument: Which one of these is safer to be in on the road?

A: The Buick isn’t that old and does incorporate many modern safety features like unit-body construction, side impact beams, crush zones and air bags. Given a choice, I’d take the Buick. In my opinion bigger is better — mass wins.

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