Quote:
Ross wrote:
Having fluid at atmospheric pressure on one side of a seal does not constitute a "strain" on a seal. Check out any engineering handbook about seals.
Your unit is worn out; the seals are shot and not sealing. The piston may or may not have pits on it. There is dirt that can hold the compensator open. Have someone rebuild it.
Ross,
Point taken. I'm not waffling on getting it rebuilt, just trying to learn as much as I can in the process and share the information. Everything I've presented so far has been, I think, in the form of query, and not any kind of endorsement of a particular view, especially pertaining to modifications of any type. I did want to post my "temptation" to plug the port during the rebuild in order to elicit responses. I will be more careful in future to emphasize that I am bringing up points for discussion. Remember my creed: "I am not an expert."
One observation: I don't think that the fluid up against the seals is at onlyy atmospheric pressure when the brake pedal is
released, because of the vacuum present at the back side of the seals. Else, how would enough fluid be drawn into the vacuum side quickly enough to cause it to go directly to the intake manifold in quantities large enough to produce smoke for an extended period?
I can't claim to know for sure whether the smoking starts upon release of the pedal but I'm pretty sure this is the case. I'm wondering if, once the process of "sucking" begins, repeated application and
release of the brake pedal keeps the process of fluid flow into the vacuum section going. Under this condition, instead of making fluid available under pressure to the wheel cylinders, the fluid could be actually
flowing the wrong way. As has been attested by others experiencing this kind of sudden failure, "pumping" the brakes in order to try to stop is useless. My speculation is that at this point, pumping just pulls more fluid into the vacuum section each time the pedal is released.
I have observed that, after a smoking episode, the level of fluid in the reservoir is depleted a great deal, so my guess is that incremental seepage of fluid past the seals into the vaccum section would not cause the sudden complete failure of brakes, but the process described above might.
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