Toyota, Honda recalls for brake problems

what are they recalling for? sounds like things I've known for years, and which ought to be in every maintenance manual:

1) always use original style brake fluid, unless you have a very old car that predates DOT3 spec (and in that case find out what the modern equivalent of the original fluid is before purchasing) 2) pressure bleeding is preferable to pump bleeding, because pump bleeding can cause failure of MC seals (granted, the reason I've seen this happen is due to the seals riding over portions of the bore that it usually doesn't wipe, which if the car has been poorly maintained in the past may have light corrosion which abrades the seal lip - not the reason given here)

So Toyota and Honda are recalling cars because improper maintenance can cause seals to fail? Sheesh.

nate

The leak is a very slow leak. The brake light will come on first.

Jeff

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sorry nate, but this is bullshit. nothing personal because i know this is a widely propagated myth, but it's fundamentally misguided for two reasons:

i. if you disassemble the modern master cylinder, you'll find the bore to be absolutely perfect inside, particularly on modern aluminum cylinders. unless using urine for emergency brake fluid over extended periods, normal brake fluids contain corrosion inhibitors that very successfully prevent corrosion and maintain this condition. even in junkyard vehicles left open to the elements which i've examined.

ii. the piston MUST fundamentally be allowed to travel the full length of the bore and maintain pressure at all times. if for some reason there might be a problem with full travel, you want to know about it - not remain in ignorance.

now, there frequently is a coincidence for seal leakage onset happening a couple of weeks after a pumped fluid change operation, but this is because the fresh fluid is exposing prior damage the seal had accumulated - it's nothing to do with the pumping action.

seal elastomer volume and mechanical properties are a function of the fluid in which it resides. old contaminated brake fluids can mess with the seal and let it expand too much and get too soft for several reasons, one being excess moisture, another being problems with the seal conditioners. this results in the elastomer, in extreme cases, to more closely resemble half-sucked gummy bear than anything else. when new fluid is flushed, its refreshed conditioners do their job in returning the seal to a better state, but that can involve shrinkage from gummy bear size, and thus the wear it sustained in gummy bear condition becomes apparent because it no longer fits the cylinder bore the way it used to. so it leaks!

so where does this lead? imagine you had one circuit out - the one operated by the farthest piston. the first piston must then be able to travel most of the length of the bore until the second piston bottoms before it will give pressure. if the first circuit were to then fail because it's "traveling in an unused section" of the cylinder, there would be little point in having dual circuit braking.

bottom line - the brake cylinder must be able to travel the full length of the bore without fear of failure. if it can't, you want to know asap. pump bleeding is a good thing. misattribution of seal failure to it is flat out wrong. and even if there were to be some problem exposed by it [although if you ever look inside a cylinder bore, you'll see how unlikely this is] - you *want to know*.

i expect it's a confluence between someone taking short cuts with the brake fluid formulation, someone else taking short cuts on the seal elastomer formulation, resulting in an especially bad care of seal gummy bear syndrome.

and based on some stuff i've seen, i think this problem is /much/ more widespread among other manufacturers. the fact that honda and toyota have stepped up to the plate is a good thing. i doubt you'll find domestics doing it - even though i guarantee you, they're not immune.

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The "Honda rep" above is "Honda PR Manager Christina Ra", so taking the notice with a grain of salt might be called for. The original brake fluid is a DOT-3 type. Both Honda and Toyota say their brake fluid includes lubricants that aftermarket brake fluids do not, but they do not say the aftermarket fluids don't meet DOT-3 specs.

It looks like the Toyota fiasco has resulted in car manufactures being a bit quicker on the trigger MLD