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Automotive/2000 Honda Odyssey Brake Problems

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Question
My daughter was driving when she heard a pop from the front end and brake pedal went to the floor.  No warning lights came on.  After sitting a day, I took a look at it.  Master Cylinder is full of fluid, not leaking fluid anywhere on vehicle.  Started it up, drove short way, but whole time, had plenty of brake pedal.  No visible damage to lines, master cylinder, or abs module.  Checked fuses and they were fine.  Dumbfounded and just hate to say, "it's ok, til it happens again", and have her get into an accident if brakes fail again.

Answer
LEAVE THE CAR PARKED, and GET the MASTER CYLINDER CHECKED AND SERVICES BEFORE YOU DRIVE THE CAR AGAIN!

In general, brake problems of the type where the pedal goes to the floor while no external leak occurs indicate a failure of the sealing surface between a master cylinder piston cup and the walls of the master cylinder (older, and fairly typical for - in example - pre-1966 American cars which had single-cylinder - non-redundant - systems) or else in the one-way check valve that admits fluid from the M/C reservoir to the working cylinder in those systems which relied on an intrusion-type displacement rod rather than a piston cup to reduce the volume and thus increase the pressure.  

With the latter type, a leak in the reservoir/cylinder check valve will bypass fluid withOUT an external leak being evident, however, it is also possible for leakage to occur through a defective gland seal through which the displacement rod itself passes.  Depending on the mounting configuration, fluid leaking from this seal might not be immediately evident - although that point might be considered moot if no drop in reservoir fluid level is noted.  [Just as an aside, there was at least one early "power" brake system (Bendix TreadleVac) in which the vacuum-assist chamber shared the SAME gland seal; with those systems, a failing seal could lose fluid to the vacuum chamber, with NO external leakage noted, plus this could happen progressively while on a road trip in any case!  

Regardless of whether the system is a piston type or a displacement type, the outcome is that the braking pressure which should result in flow from the cylinder to the brake lines and thence to the wheel cylinders or caliper actuators is instead being relieved by being leaked back into the void behind the piston in the older type or back into the reservoir in the later and more common type.  BOTH WILL HAVE THE RESULT OF DIMINISHED AND ULTIMATELY LOSS OF BRAKING.

For this reason, I STRONGLY advise AGAINST driving the car to any repair facility.  Tow the car, or trailer it, or repair it / have it repaired on site.

Regards ... EGK

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Ernest (Ernie) Kenward

Expertise

The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!

Experience

A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

Organizations
IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Education/Credentials
Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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